Configuration

• 1: WebUI Configuration
• 2: Confd and Confcli
• 3: Session Groups and Classification
• 4: Advanced features
• 4.1: Content popularity
• 4.2: Consistent Hashing
• 4.3: Predictive load balancing
• 4.4: Security token verification
• 4.5: Subnets API
• 4.6: Lua Features
• 4.6.1: Global Lua Tables
• 4.6.2: Health Check Functions
• 4.6.3: Request Translation Function
• 4.6.4: Session Translation Function
• 4.6.5: Host Request Translation Function
• 4.6.6: Response Translation Function
• 5: Trusted proxies
• 6: Confd Auto Upgrade Tool

1 - WebUI Configuration

The web based user interface is installed as a separate component and can be used to configure many common use cases. After navigating to the UI, a login screen will be presented.

Enter your credentials and log in. In the top left corner is a menu to select what section of the configuration to change. The configuration that will be active on the router is added in the Routing Workflow view. However, basic elements such as classification rules and routing targets, etc must be added first. Hence the following main steps are required to produce a proper configuration:

1. Create classifiers serving as basic elements to create session groups.
2. Create session groups which, using the classifiers, tag requests/clients for later use in the routing logic. of the incoming traffic.
3. Define offload rules.
4. Define rules to control behavior of internal traffic.
5. Define backup rules to be used if the routing targets in the above step are unavailable.
6. Finally, create the desired routing workflow using the elements defined in the previous steps.

A simplified concrete example of the above steps could be:

• Create two classifiers “smartphone” and “off-net”.
• Create a session group “mobile off-net”.
• Offload off-net traffic from mobile phones to a public CDN.
• Route other traffic to a private CDN.
• If the private CDN has an outage, use the public CDN for all traffic.

Hence, to start with, define the classifiers you will need. Those are based on information in the incoming request, optionally in combination with GeoIP databases or subnet information configured via the Subnet API. Here we show how to set up a GeoIP classifier. Note that the Director ships with a compatible snapshot of the GeoIP database, but for a production system a licensed and updated database is required.

Click the plus sign indicated in the picture above to create a new GeoIP classifier. You will be presented with the following view:

Here you can enter the geographical data on which to match, or check the “Inverted” check box to match anything except the entered geographical data.

The other kinds of classifiers are configured in a similar way.

After having added all the classifiers you need, it is time to create the session groups. Those are named filters that group incoming requests, typically video playback sessions in a video streaming CDN, and are defined with the help of the classifiers. For example, a session group “off-net mobile devices” could be composed of the classifiers “off-net traffic” and “mobile devices”.

Open the Session Groups view from the menu and hit the plus sign to add a new session group.

Define the new sessions groups by combining the previously created classifiers. It is often convenient to define an “All” session group that matches any incoming request.

Next go the “CDN Offload” view:

Here you define conditions for CDN offload. Each row defines a rule for offloading a specified session group. The rule makes use of the Selection Input API. This is an integration API that provides a way to supply additional data for use in the routing decision. Common examples are current bitrates or availability status. The selection input variables to use must be defined in the “Selection Input Types” view in the “Administration” section of the menu:

Reach out to the solution engineers from Agile Content in order to perform this integration in the best way. If no external data is required, such that the offload rule can be based solely based on session groups, this is not necessary and the condition field can be set to “Always” or “Disabled”.

When clicking the plus sign to add a new CDN Offload rule, the following view is presented:

The selection input rule is phrased in terms of a variable being above or below a threshold, but also a state such as “available” taking values 0 or 1 can be supported by for instance checking if “available” is below 1.

Moving on, if an incoming request is not offloaded, it will be handled by the Primary CDN section of the routing configuration.

Add all hosts in your primary CDN, together with a weight. A row in this table will be selected by random weighted load balancing. If each weight is the same, each row will be selected with the same probability. Another example would be three rows with weights 100, 100 and 200 which would randomly balance 50% of the load on the last row and the remaining load on the first two rows, i.e. 25% on each of the first and second row. If a Primary CDN host is unavailable, that host will not take part in the random selection.

If all hosts are unavailable, as a final resort the routing evaluation will go to the final Backup CDN step:

Here you can define what to do when all else fail. If not all requests are covered, for example with an “All” session group, then the request will fail with 403 Forbidden.

Now you have defined the basic elements and it is time to define the routing workflow. Select “Routing Workflow” from the menu, as pictured below. Here you can combine the elements previously created to achieve the desired routing behavior.

When everything seems correct, open the “Publish Routing” view from the menu:

Hit “Publish All Changes” and verify that you get a successful result.

2 - Confd and Confcli

Configuration of a complex routing tree can be difficult. The command line interface tool called confcli has been developed to make it simpler. It combines building blocks, representing simple routing decisions, into complex routing trees capable of satisfying almost any routing requirements.

These blocks are translated into an ESB3024 Router configuration which is automatically sent to the router, overwriting existing routing rules, CDN list and host list.

Installation and Usage

The confcli tools are installed alongside ESB3024 Router, on the same host, and the confcli command line tool itself is made available on the host machine.

Simply type confcli in a shell on the host to see the current routing configuration:

$ confcli
{
    "services": {
        "routing": {
            "settings": {
                "trustedProxies": [],
                "contentPopularity": {
                    "algorithm": "score_based",
                    "sessionGroupNames": []
                },
                "extendedContentIdentifier": {
                    "enabled": false,
                    "includedQueryParams": []
                },
                "instream": {
                    "dashManifestRewrite": {
                        "enabled": false,
                        "sessionGroupNames": []
                    },
                    "hlsManifestRewrite": {
                        "enabled": false,
                        "sessionGroupNames": []
                    },
                    "reversedFilenameComparison": false
                },
                "usageLog": {
                    "enabled": false,
                    "logInterval": 3600000
                }
            },
            "tuning": {
                "content": {
                    "cacheSizeFullManifests": 1000,
                    "cacheSizeLightManifests": 10000,
                    "lightCacheTimeMilliseconds": 86400000,
                    "liveCacheTimeMilliseconds": 100,
                    "vodCacheTimeMilliseconds": 10000
                },
                "general": {
                    "accessLog": false,
                    "coutFlushRateMilliseconds": 1000,
                    "cpuLoadWindowSize": 10,
                    "eagerCdnSwitching": false,
                    "httpPipeliningEnable": false,
                    "logLevel": 3,
                    "maxConnectionsPerHost": 5,
                    "overloadThreshold": 32,
                    "readyThreshold": 8,
                    "redirectingCdnManifestDownloadRetries": 2,
                    "repeatedSessionStartThresholdSeconds": 30,
                    "selectionInputMetricsTimeoutSeconds": 30
                },
                "session": {
                    "idleDeactivateTimeoutMilliseconds": 20000,
                    "idleDeleteTimeoutMilliseconds": 1800000
                },
                "target": {
                    "responseTimeoutSeconds": 5,
                    "retryConnectTimeoutSeconds": 2,
                    "retryResponseTimeoutSeconds": 2,
                    "connectTimeoutSeconds": 5,
                    "maxIdleTimeSeconds": 30,
                    "requestAttempts": 3
                }
            },
            "sessionGroups": [],
            "classifiers": [],
            "hostGroups": [],
            "rules": [],
            "entrypoint": "",
            "applyConfig": true
        }
    }
}

The CLI tool can be used to modify, add and delete values by providing it with the “path” to the object to change. The path is constructed by joining the field names leading up to the value with a period between each name, e.g. the path to the entrypoint is services.routing.entrypoint since entrypoint is nested under the routing object, which in turn is under the services root object. Lists use an index number in place of a field name, where 0 indicates the very first element in the list, 1 the second element and so on.

If the list contains objects which have a field with the name name, the index number can be replaced by the unique name of the object of interest.

Tab completion is supported by confcli. Pressing tab once will complete as far as possible, and pressing tab twice will list all available alternatives at the path constructed so far.

Display the values at a specific path:

$ confcli services.routing.hostGroups
{
    "hostGroups": [
        {
            "name": "internal",
            "type": "redirecting",
            "httpPort": 80,
            "httpsPort": 443,
            "hosts": [
                {
                    "name": "rr1",
                    "hostname": "rr1.example.com",
                    "ipv6_address": ""
                }
            ]
        },
        {
            "name": "external",
            "type": "host",
            "httpPort": 80,
            "httpsPort": 443,
            "hosts": [
                {
                    "name": "offload-streamer1",
                    "hostname": "streamer1.example.com",
                    "ipv6_address": ""
                },
                {
                    "name": "offload-streamer2",
                    "hostname": "streamer2.example.com",
                    "ipv6_address": ""
                }
            ]
        }
    ]
}

Display the values in a specific list index:

$ confcli services.routing.hostGroups.1
{
    "1": {
        "name": "external",
        "type": "host",
        "httpPort": 80,
        "httpsPort": 443,
        "hosts": [
            {
                "name": "offload-streamer1",
                "hostname": "streamer1.example.com",
                "ipv6_address": ""
            },
            {
                "name": "offload-streamer2",
                "hostname": "streamer2.example.com",
                "ipv6_address": ""
            }
        ]
    }
}

Display the values in a specific list index using the object’s name:

$ confcli services.routing.hostGroups.1.hosts.offload-streamer2
{
    "offload-streamer2": {
        "name": "offload-streamer2",
        "hostname": "streamer2.example.com",
        "ipv6_address": ""
    }
}

Modify a single value:

confcli services.routing.hostGroups.1.hosts.offload-streamer2.hostname new-streamer.example.com
services.routing.hostGroups.1.hosts.offload-streamer2.hostname = 'new-streamer.example.com'

Delete an entry:

$ confcli services.routing.sessionGroups.Apple.classifiers.
{
    "classifiers": [
        "Apple",
        ""
    ]
}

$ confcli services.routing.sessionGroups.Apple.classifiers.1 -d
http://localhost:5000/config/__active/services/routing/sessionGroups/Apple/classifiers/1 reset to default/deleted

$ confcli services.routing.sessionGroups.Apple.classifiers.
{
    "classifiers": [
        "Apple"
    ]
}

Adding new values in objects and lists is done using a wizard by invoking confcli with a path and the -w argument. This will be shown extensively in the examples further down in this document rather than here.

If you have a JSON file with a previously generated confcli configuration output it can be applied to a system by typing confcli -i <file path>.

CDNs and Hosts

Configuration using confcli has no real concept of CDNs, instead it has groups of hosts that share some common settings such as HTTP(S) port and whether they return a redirection URL, serve content directly or perform a DNS lookup. Of these three variants, the two former share the same parameters, while the DNS variant is slightly different.

Each host belongs to a host group and may itself be an entire CDN using a single public hostname or a single streamer server, all depending on the needs of the user.

Host Health

When creating a host in the confd configuration, you have the option to define a list of health check functions. Each health check function must return true for a host to be selected. This means that the host will only be considered available if all the defined health check functions evaluate to true. If any of the health check functions return false, the host will be considered unavailable and will not be selected for routing. All health check functions are detailed in the section Health Check Functions.

• Redirecting/Host
• DNS

$ confcli services.routing.hostGroups -w
Running wizard for resource 'hostGroups'

Hint: Hitting return will set a value to its default.
Enter '?' to receive the help string

hostGroups : [
  hostGroup can be one of
    1: dns
    2: host
    3: redirecting
  Choose element index or name: redirecting
  Adding a 'redirecting' element
    hostGroup : {
      name (default: ): edgeware
      type (default: redirecting): ⏎
      httpPort (default: 80): ⏎
      httpsPort (default: 443): ⏎
      hosts : [
        host : {
          name (default: ): rr1
          hostname (default: ): convoy-rr1.example.com
          ipv6_address (default: ): ⏎
          healthChecks : [
            healthCheck (default: always()): basic_health_check()
            Add another 'healthCheck' element to array 'healthChecks'? [y/N]: n
          ]
        }
        Add another 'host' element to array 'hosts'? [y/N]: y
        host : {
          name (default: ): rr2
          hostname (default: ): convoy-rr2.example.com
          ipv6_address (default: ): ⏎
          healthChecks : [
            healthCheck (default: always()): ⏎
            Add another 'healthCheck' element to array 'healthChecks'? [y/N]: n
          ]
        }
        Add another 'host' element to array 'hosts'? [y/N]: ⏎
      ]
    }
  Add another 'hostGroup' element to array 'hostGroups'? [y/N]: ⏎
]
Generated config:
{
  "hostGroups": [
    {
      "name": "edgeware",
      "type": "redirecting",
      "httpPort": 80,
      "httpsPort": 443,
      "hosts": [
        {
          "name": "rr1",
          "hostname": "convoy-rr1.example.com",
          "ipv6_address": "",
          "healthChecks": [
            "basic_health_check()"
          ]
        },
        {
          "name": "rr2",
          "hostname": "convoy-rr2.example.com",
          "ipv6_address": "",
          "healthChecks": [
            "always()"
          ]
        }
      ]
    }
  ]
}
Merge and apply the config? [y/n]: y
  

$ confcli services.routing.hostGroups -w
Running wizard for resource 'hostGroups'

Hint: Hitting return will set a value to its default.
Enter '?' to receive the help string

hostGroups : [
  hostGroup can be one of
    1: dns
    2: host
    3: redirecting
  Choose element index or name: dns
  Adding a 'dns' element
    hostGroup : {
      name (default: ): external-dns
      type (default: dns): ⏎
      hosts : [
        host : {
          name (default: ): dns-host
          hostname (default: ): dns.example.com
          ipv6_address (default: ): ⏎
          healthChecks : [
            healthCheck (default: always()): ⏎
            Add another 'healthCheck' element to array 'healthChecks'? [y/N]: n
          ]
        }
        Add another 'host' element to array 'hosts'? [y/N]: ⏎
      ]
    }
  Add another 'hostGroup' element to array 'hostGroups'? [y/N]: ⏎
]
Generated config:
{
  "hostGroups": [
    {
      "name": "external-dns",
      "type": "dns",
      "hosts": [
        {
          "name": "dns-host",
          "hostname": "dns.example.com",
          "ipv6_address": "",
          "healthChecks": [
            "always()"
          ]
        }
      ]
    }
  ]
}
Merge and apply the config? [y/n]: y
  

Rule Blocks

The routing configuration using confcli is done using a combination of logical building blocks, or rules. Each block evaluates the incoming request in some way and sends it on to one or more sub-blocks. If the block is of the host type described above, the client is sent to that host and the evaluation is done.

Existing blocks

Currently supported blocks are:

• allow: Incoming requests, for which a given rule function matches, are immediately sent to the provided onMatch target.
• consistentHashing: Splits incoming requests randomly between preferred hosts, determined by the proprietary consistent hashing algorithm. The amount of hosts to split between is controlled by the spreadFactor.
• contentPopularity: Splits incoming requests into two sub-blocks depending on how popular the requested content is.
• deny: Incoming requests, for which a given rule function matches, are immediately denied, and all non-matching requests are sent to the onMiss target.
• firstMatch: Incoming requests are matched by an ordered series of rules, where the request will be handled by the first rule for which the condition evaluates to true.
• random: Splits incoming requests randomly and equally between a list of target sub-blocks. Useful for simple load balancing.
• split: Splits incoming requests between two sub-blocks depending on how the request is evaluated by a provided function. Can be used for sending clients to different hosts depending on e.g. geographical location or client hardware type.
• weighted: Randomly splits incoming requests between a list of target sub-blocks, weighted according to each target’s associated weight rule. A higher weight means a higher portion of requests will be routed to a sub-block. Rules can be used to decide whether or not to pick a target.
• rawGroup: Contains a raw ESB3024 Router configuration routing tree node, to be inserted as is in the generated configuration. This is only meant to be used in the rare cases when it’s impossible to construct the required routing behavior in any other way.
• rawHost: A host reference for use as endpoints in rawGroup trees.

• Allow
• Consistent Hashing
• Content Popularity
• Deny
• First Match
• Random
• Split
• Weighted
• Raw

$ confcli services.routing.rules -w
Running wizard for resource 'rules'

Hint: Hitting return will set a value to its default.
Enter '?' to receive the help string

rules : [
  rule can be one of
    1: allow
    2: consistentHashing
    3: contentPopularity
    4: deny
    5: firstMatch
    6: random
    7: rawGroup
    8: rawHost
    9: split
    10: weighted
  Choose element index or name: allow
  Adding a 'allow' element
    rule : {
      name (default: ): allow
      type (default: allow): ⏎
      condition (default: ): customFunction()
      onMatch (default: ): rr1
    }
  Add another 'rule' element to array 'rules'? [y/N]: ⏎
]
Generated config:
{
  "rules": [
    {
      "name": "content",
      "type": "contentPopularity",
      "condition": "customFunction()",
      "onMatch": "rr1"
    }
  ]
}
Merge and apply the config? [y/n]: y

$ confcli services.routing.rules -w
Running wizard for resource 'rules'

Hint: Hitting return will set a value to its default.
Enter '?' to receive the help string

rules : [
  rule can be one of
    1: allow
    2: consistentHashing
    3: contentPopularity
    4: deny
    5: firstMatch
    6: random
    7: rawGroup
    8: rawHost
    9: split
    10: weighted
  Choose element index or name: consistentHashing
  Adding a 'consistentHashing' element
    rule : {
      name (default: ): consistentHashingRule
      type (default: consistentHashing): 
      spreadFactor (default: 1): 2
      hashAlgorithm (default: MD5):
      targets : [
        target : {
          target (default: ): rr1
          enabled (default: True): 
        }
        Add another 'target' element to array 'targets'? [y/N]: y
        target : {
          target (default: ): rr2
          enabled (default: True): 
        }
        Add another 'target' element to array 'targets'? [y/N]: y
        target : {
          target (default: ): rr3
          enabled (default: True): 
        }
        Add another 'target' element to array 'targets'? [y/N]: n
      ]
    }
  Add another 'rule' element to array 'rules'? [y/N]: n
]
Generated config:
{
  "rules": [
    {
      "name": "consistentHashingRule",
      "type": "consistentHashing",
      "spreadFactor": 2,
      "hashAlgorithm": "MD5",
      "targets": [
        {
          "target": "rr1",
          "enabled": true
        },
        {
          "target": "rr2",
          "enabled": true
        },
        {
          "target": "rr3",
          "enabled": true
        }
      ]
    }
  ]
}
Merge and apply the config? [y/n]: y

$ confcli services.routing.rules -w
Running wizard for resource 'rules'

Hint: Hitting return will set a value to its default.
Enter '?' to receive the help string

rules : [
  rule can be one of
    1: allow
    2: consistentHashing
    3: contentPopularity
    4: deny
    5: firstMatch
    6: random
    7: rawGroup
    8: rawHost
    9: split
    10: weighted
  Choose element index or name: contentPopularity
  Adding a 'contentPopularity' element
    rule : {
      name (default: ): content
      type (default: contentPopularity): ⏎
      contentPopularityCutoff (default: 10): 20
      onPopular (default: ): rr1
      onUnpopular (default: ): rr2
    }
  Add another 'rule' element to array 'rules'? [y/N]: ⏎
]
Generated config:
{
  "rules": [
    {
      "name": "content",
      "type": "contentPopularity",
      "contentPopularityCutoff": 20.0,
      "onPopular": "rr1",
      "onUnpopular": "rr2"
    }
  ]
}
Merge and apply the config? [y/n]: y

$ confcli services.routing.rules -w
Running wizard for resource 'rules'

Hint: Hitting return will set a value to its default.
Enter '?' to receive the help string

rules : [
  rule can be one of
    1: allow
    2: consistentHashing
    3: contentPopularity
    4: deny
    5: firstMatch
    6: random
    7: rawGroup
    8: rawHost
    9: split
    10: weighted
  Choose element index or name: deny
  Adding a 'deny' element
    rule : {
      name (default: ): deny
      type (default: deny): ⏎
      condition (default: ): customFunction()
      onMiss (default: ): rr1
    }
  Add another 'rule' element to array 'rules'? [y/N]: ⏎
]
Generated config:
{
  "rules": [
    {
      "name": "content",
      "type": "contentPopularity",
      "condition": "customFunction()",
      "onMiss": "rr1"
    }
  ]
}
Merge and apply the config? [y/n]: y

$ confcli services.routing.rules -w
Running wizard for resource 'rules'

Hint: Hitting return will set a value to its default.
Enter '?' to receive the help string

rules : [
  rule can be one of
    1: allow
    2: consistentHashing
    3: contentPopularity
    4: deny
    5: firstMatch
    6: random
    7: rawGroup
    8: rawHost
    9: split
    10: weighted
  Choose element index or name: firstMatch
  Adding a 'firstMatch' element
    rule : {
      name (default: ): firstMatch
      type (default: firstMatch): ⏎
      targets : [
        target : {
          onMatch (default: ): rr1
          rule (default: ): customFunction()
        }
        Add another 'target' element to array 'targets'? [y/N]: y
        target : {
          onMatch (default: ): rr2
          rule (default: ): otherCustomFunction()
        }
        Add another 'target' element to array 'targets'? [y/N]: n
      ]
    }
  Add another 'rule' element to array 'rules'? [y/N]: n
]
Generated config:
{
  "rules": [
    {
      "name": "firstMatch",
      "type": "firstMatch",
      "targets": [
        {
          "onMatch": "rr1",
          "condition": "customFunction()"
        },
        {
          "onMatch": "rr2",
          "condition": "otherCustomFunction()"
        }
      ]
    }
  ]
}
Merge and apply the config? [y/n]: y

$ confcli services.routing.rules -w
Running wizard for resource 'rules'

Hint: Hitting return will set a value to its default.
Enter '?' to receive the help string

rules : [
  rule can be one of
    1: allow
    2: consistentHashing
    3: contentPopularity
    4: deny
    5: firstMatch
    6: random
    7: rawGroup
    8: rawHost
    9: split
    10: weighted
  Choose element index or name: random
  Adding a 'random' element
    rule : {
      name (default: ): random
      type (default: random): ⏎
      targets : [
        target (default: ): rr1
        Add another 'target' element to array 'targets'? [y/N]: y
        target (default: ): rr2
        Add another 'target' element to array 'targets'? [y/N]: ⏎
      ]
    }
  Add another 'rule' element to array 'rules'? [y/N]: ⏎
]
Generated config:
{
  "rules": [
    {
      "name": "random",
      "type": "random",
      "targets": [
        "rr1",
        "rr2"
      ]
    }
  ]
}
Merge and apply the config? [y/n]: y
  

$ confcli services.routing.rules -w
Running wizard for resource 'rules'

Hint: Hitting return will set a value to its default.
Enter '?' to receive the help string

rules : [
  rule can be one of
    1: allow
    2: consistentHashing
    3: contentPopularity
    4: deny
    5: firstMatch
    6: random
    7: rawGroup
    8: rawHost
    9: split
    10: weighted
  Choose element index or name: split
  Adding a 'split' element
    rule : {
      name (default: ): split
      type (default: split): ⏎
      condition (default: ): custom_function()
      onMatch (default: ): rr2
      onMiss (default: ): rr1
    }
  Add another 'rule' element to array 'rules'? [y/N]: ⏎
]
Generated config:
{
  "rules": [
    {
      "name": "split",
      "type": "split",
      "condition": "custom_function()",
      "onMatch": "rr2",
      "onMiss": "rr1"
    }
  ]
}
Merge and apply the config? [y/n]: y
  

$ confcli services.routing.rules. -w
Running wizard for resource 'rules'

Hint: Hitting return will set a value to its default.
Enter '?' to receive the help string

rules : [
  rule can be one of
    1: allow
    2: consistentHashing
    3: contentPopularity
    4: deny
    5: firstMatch
    6: random
    7: rawGroup
    8: rawHost
    9: split
    10: weighted
  Choose element index or name: weighted
  Adding a 'weighted' element
    rule : {
      name (default: ): weight
      type (default: weighted): ⏎
      targets : [
        target : {
          target (default: ): rr1
          weight (default: 100): ⏎
          condition (default: always()): always()
        }
        Add another 'target' element to array 'targets'? [y/N]: y
        target : {
          target (default: ): rr2
          weight (default: 100): si('rr2-input-weight')
          condition (default: always()): gt('rr2-bandwidth', 1000000)
        }
        Add another 'target' element to array 'targets'? [y/N]: y
        target : {
          target (default: ): rr2
          weight (default: 100): custom_func()
          condition (default: always()): always()
        }
        Add another 'target' element to array 'targets'? [y/N]: ⏎
      ]
    }
  Add another 'rule' element to array 'rules'? [y/N]: ⏎
]
Generated config:
{
  "rules": [
    {
      "name": "weight",
      "type": "weighted",
      "targets": [
        {
          "target": "rr1",
          "weight": "100",
          "condition": "always()"
        },
        {
          "target": "rr2",
          "weight": "si('rr2-input-weight')",
          "condition": "gt('rr2-bandwith', 1000000)"
        },
        {
          "target": "rr2",
          "weight": "custom_func()",
          "condition": "always()"
        }
      ]
    }
  ]
}
Merge and apply the config? [y/n]: y
  

>> First add a raw host block that refers to a regular host

$ confcli services.routing.rules. -w
Running wizard for resource 'rules'

Hint: Hitting return will set a value to its default.
Enter '?' to receive the help string

rules : [
  rule can be one of
    1: allow
    2: consistentHashing
    3: contentPopularity
    4: deny
    5: firstMatch
    6: random
    7: rawGroup
    8: rawHost
    9: split
    10: weighted
  Choose element index or name: rawHost
  Adding a 'rawHost' element
    rule : {
      name (default: ): raw-host
      type (default: rawHost): ⏎
      hostId (default: ): rr1
    }
  Add another 'rule' element to array 'rules'? [y/N]: ⏎
]
Generated config:
{
  "rules": [
    {
      "name": "raw-host",
      "type": "rawHost",
      "hostId": "rr1"
    }
  ]
}
Merge and apply the config? [y/n]: y

>> And then add a rule using the host node

$ confcli services.routing.rules. -w
Running wizard for resource 'rules'

Hint: Hitting return will set a value to its default.
Enter '?' to receive the help string

rules : [
  rule can be one of
    1: allow
    2: consistentHashing
    3: contentPopularity
    4: deny
    5: firstMatch
    6: random
    7: rawGroup
    8: rawHost
    9: split
    10: weighted
  Choose element index or name: rawGroup
  Adding a 'rawGroup' element
    rule : {
      name (default: ): raw-node
      type (default: rawGroup): ⏎
      memberOrder (default: sequential): ⏎
      members : [
        member : {
          target (default: ): raw-host
          weightFunction (default: ): return 1
        }
        Add another 'member' element to array 'members'? [y/N]: ⏎
      ]
    }
  Add another 'rule' element to array 'rules'? [y/N]: ⏎
]
Generated config:
{
  "rules": [
    {
      "name": "raw-node",
      "type": "rawGroup",
      "memberOrder": "sequential",
      "members": [
        {
          "target": "raw-host",
          "weightFunction": "return 1"
        }
      ]
    }
  ]
}
Merge and apply the config? [y/n]: y
  

Rule Language

Some blocks, such as the split and firstMatch types, have a rule field that contains a small function in a very simple programming language. This field is used to filter any incoming client requests in order to determine how to rule block should react.

In the case of a split block, the rule is evaluated and if it is true the client is sent to the onMatch part of the block, otherwise it is sent to the onMiss part for further evaluation.

In the case of a firstMatch block, the rule for each target will be evaluated top to bottom in order until either a rule evaluates to true or the list is exhausted. If a rule evaluates to true, the client will be sent to the onMatch part of the block, otherwise the next target in the list will be tried. If all targets have been exhausted, then the entire rule evaluation will fail, and the routing tree will be restarted with the firstMatch block effectively removed.

Example of Boolean Functions

Let’s say we have an ESB3024 Router set up with a session group that matches Apple devices (named “Apple”). To route all Apple devices to a specific streamer one would simply create a split block with the following rule:

in_session_group('Apple')

In order to make more complex rules it’s possible to combine several checks like this in the same rule. Let’s extend the hypothetical ESB3024 Router above with a configured subnet with all IP addresses in Europe (named “Europe”). To make a rule that accepts any clients using an Apple device and living outside of Europe, but only as long as the reported load on the streamer (as indicated by the selection input variable “europe_load_mbps”) is less than 1000 megabits per second one could make an offload block with the following rule (without linebreaks):

in_session_group('Apple')
    and not in_subnet('Europe')
    and lt('europe_load_mbps', 1000)

In this example in_session_group('Apple') will be true if the client belongs to the session group named ‘Apple’. The function call in_subnet('Europe') is true if the client’s IP belongs to the subnet named ‘Europe’, but the word not in front of it reverses the value so the entire section ends up being false if the client is in Europe. Finally lt('europe_load_mbps', 1000) is true if there is a selection input variable named “europe_load_mbps” and its value is less than 1000.

Since the three parts are conjoined with the and keyword they must all be true for the entire rule to match. If the keyword or had been used instead it would have been enough for any of the parts to be true for the rule to match.

Example of Numeric Functions

A hypothetical CDN has two streamers with different capacity; Host_1 has roughly twice the capacity of Host_2. A simple random load balancing would put undue stress on the second host since it will receive as much traffic as the more capable Host_1.

This can be solved by using a weighted random distribution rule block with suitable rules for the two hosts:

{
    "targets": [
        {
            "target": "Host_1",
            "condition": "always()",
            "weight": "100"
        }
        {
            "target": "Host_2",
            "condition": "always()",
            "weight": "50"
        },
    ]
}

resulting in Host_1 receiving twice as many requests as Host_2 as its weight function is double that of Host_2.

If the CDN is capable of reporting the free capacity of the hosts, for example by writing to a selection input variable for each host, it’s easy to write a more intelligent load balancing rule by making the weights correspond to the amount of capacity left on each host:

{
    "targets": [
        {
            "target": "Host_1",
            "condition": "always()",
            "weight": "si('free_capacity_host_1')"
        }
        {
            "target": "Host_2",
            "condition": "always()",
            "weight": "si('free_capacity_host_2')"
        },
    ]
}

It is also possible to write custom Lua functions that return suitable weights, perhaps taking the host as an argument:

{
    "targets": [
        {
            "target": "Host_1",
            "condition": "always()",
            "weight": "intelligent_weight_function('Host_1')"
        }
        {
            "target": "Host_2",
            "condition": "always()",
            "weight": "intelligent_weight_function('Host_1')"
        },
    ]
}

These different weight rules can of course be combined in the same rule block, with one target having a hard coded number, another using a dynamically updated selection input variable and yet another having a custom-built function.

Due to limitations in the random number generator used to distribute requests, it’s better to use somewhat large values, around 100–1000 or so, than to use small values near 0.

Built-in Functions

The following built-in functions are available when writing rules:

• in_session_group(str name): True if session belongs to session group <name>
• in_all_session_groups(str sg_name, ...): True if session belongs to all specified session groups
• in_any_session_group(str sg_name, ...): True if session belongs to any specified session group
• in_subnet(str subnet_name): True if client IP belongs to the named subnet
• gt(str si_var, number value): True if selection_inputs[si_var] > value
• gt(str si_var1, str si_var2): True if selection_inputs[si_var1] > selection_inputs[si_var2]
• ge(str si_var, number value): True if selection_inputs[si_var] >= value
• ge(str si_var1, str si_var2): True if selection_inputs[si_var1] >= selection_inputs[si_var2]
• lt(str si_var, number value): True if selection_inputs[si_var] < value
• lt(str si_var1, str si_var2): True if selection_inputs[si_var1] < selection_inputs[si_var2]
• le(str si_var, number value): True if selection_inputs[si_var] <= value
• le(str si_var1, str si_var2): True if selection_inputs[si_var1] <= selection_inputs[si_var2]
• eq(str si_var, number value): True if selection_inputs[si_var] == value
• eq(str si_var1, str si_var2): True if selection_inputs[si_var1] == selection_inputs[si_var2]
• neq(str si_var, number value): True if selection_inputs[si_var] != value
• neq(str si_var1, str si_var2): True if selection_inputs[si_var1] != selection_inputs[si_var2]
• si(str si_var): Returns the value of selection_inputs[si_var] if it is defined and non-negative, otherwise it returns 0.
• always(): Returns true, useful when creating weighted rule blocks.
• never(): Returns false, opposite of always().

These functions, as well as custom functions written in Lua and uploaded to the ESB3024 Router, can be combined to make suitably precise rules.

Combining Multiple Boolean Functions

In order to make the rule language easy to work with, it is fairly restricted and simple. One restriction is that it’s only possible to chain multiple function results together using either and or or, but not a combination of both conjunctions.

Statements joined with and or or keywords are evaluated one by one, starting with the left-most statement and moving right. As soon as the end result of the entire expression is certain, the evaluation ends. This means that evaluation ends with the first false statement for and expressions since a single false component means the entire expression must also be false. It also means that evaluation ends with the first true statement for or expressions since only one component must be true for the entire statement to be true as well. This is known as short-circuit or lazy evaluation.

Custom Functions

It is possible to write extremely complex Lua functions that take many parameters or calculations into consideration when evaluating an incoming client request. By writing such functions and making sure that they return only non-negative integer values and uploading them to the router they can be used from the rule language. Simply call them like any of the built-in functions listed above, using strings and numbers as arguments if necessary, and their result will be used to determine the routing path to use.

Formal Syntax

The full syntax of the language can be described in just a few lines of BNF grammar:

<rule>               := <weight_rule> | <match_rule> | <value_rule>
<weight_rule>        := "if" <compound_predicate> "then" <weight> "else" <weight>
<match_rule>         := <compound_predicate>
<value_rule>         := <weight>
<compound_predicate> := <logical_predicate> |
                        <logical_predicate> ["and" <logical_predicate> ...] |
                        <logical_predicate> ["or" <logical_predicate> ...] |
<logical_predicate>  := ["not"] <predicate>
<predicate>          := <function_name> "(" ")" |
                        <function_name> "(" <argument> ["," <argument> ...] ")"
<function_name>      := <letter> [<function_name_tail> ...]
<function_name_tail> := empty | <letter> | <digit> | "_"
<argument>           := <string> | <number>
<weight>             := integer | <predicate>
<number>             := float | integer
<string>             := "'" [<letter> | <digit> | <symbol> ...] "'"

Building a Routing Configuration

This example sets up an entire routing configuration for a system with a ESB3008 Request Router, two streamers and the Apple devices outside of Europe example used earlier in this document. Any clients not matching the criteria will be sent to an offload CDN with two streamers in a simple uniformly randomized load balancing setup.

Set up Session Group

First make a classifier and a session group that uses it:

$ confcli services.routing.classifiers -w
Running wizard for resource 'classifiers'

Hint: Hitting return will set a value to its default.
Enter '?' to receive the help string

classifiers : [
  classifier can be one of
    1: anonymousIp
    2: asnIds
    3: contentUrlPath
    4: contentUrlQueryParameters
    5: geoip
    6: hostName
    7: ipranges
    8: random
    9: regexMatcher
    10: stringMatcher
    11: subnet
    12: userAgent
  Choose element index or name: userAgent
  Adding a 'userAgent' element
    classifier : {
      name (default: ): Apple
      type (default: userAgent): ⏎
      inverted (default: False): ⏎
      patternType (default: stringMatch): ⏎
      pattern (default: ): *apple*
    }
  Add another 'classifier' element to array 'classifiers'? [y/N]: ⏎
]
Generated config:
{
  "classifiers": [
    {
      "name": "Apple",
      "type": "userAgent",
      "inverted": false,
      "patternType": "stringMatch",
      "pattern": "*apple*"
    }
  ]
}
Merge and apply the config? [y/n]: y

$ confcli services.routing.sessionGroups -w
Running wizard for resource 'sessionGroups'

Hint: Hitting return will set a value to its default.
Enter '?' to receive the help string

sessionGroups : [
  sessionGroup : {
    name (default: ): Apple
    classifiers : [
      classifier (default: ): Apple
      Add another 'classifier' element to array 'classifiers'? [y/N]: ⏎
    ]
  }
  Add another 'sessionGroup' element to array 'sessionGroups'? [y/N]: ⏎
]
Generated config:
{
  "sessionGroups": [
    {
      "name": "Apple",
      "classifiers": [
        "Apple"
      ]
    }
  ]
}
Merge and apply the config? [y/n]: y

Set up Hosts

Create two host groups and add a Request Router to the first and two streamers to the second, which will be used for offload:

$ confcli services.routing.hostGroups -w
Running wizard for resource 'hostGroups'

Hint: Hitting return will set a value to its default.
Enter '?' to receive the help string

hostGroups : [
  hostGroup can be one of
    1: dns
    2: host
    3: redirecting
  Choose element index or name: redirecting
  Adding a 'redirecting' element
    hostGroup : {
      name (default: ): internal
      type (default: redirecting): ⏎
      httpPort (default: 80): ⏎
      httpsPort (default: 443): ⏎
      hosts : [
        host : {
          name (default: ): rr1
          hostname (default: ): rr1.example.com
          ipv6_address (default: ): ⏎
        }
        Add another 'host' element to array 'hosts'? [y/N]: ⏎
      ]
    }
  Add another 'hostGroup' element to array 'hostGroups'? [y/N]: y
  hostGroup can be one of
    1: dns
    2: host
    3: redirecting
  Choose element index or name: host
  Adding a 'host' element
    hostGroup : {
      name (default: ): external
      type (default: host): ⏎
      httpPort (default: 80): ⏎
      httpsPort (default: 443): ⏎
      hosts : [
        host : {
          name (default: ): offload-streamer1
          hostname (default: ): streamer1.example.com
          ipv6_address (default: ): ⏎
        }
        Add another 'host' element to array 'hosts'? [y/N]: y
        host : {
          name (default: ): offload-streamer2
          hostname (default: ): streamer2.example.com
          ipv6_address (default: ): ⏎
        }
        Add another 'host' element to array 'hosts'? [y/N]: ⏎
      ]
    }
  Add another 'hostGroup' element to array 'hostGroups'? [y/N]: ⏎
]
Generated config:
{
  "hostGroups": [
    {
      "name": "internal",
      "type": "redirecting",
      "httpPort": 80,
      "httpsPort": 443,
      "hosts": [
        {
          "name": "rr1",
          "hostname": "rr1.example.com",
          "ipv6_address": ""
        }
      ]
    },
    {
      "name": "external",
      "type": "host",
      "httpPort": 80,
      "httpsPort": 443,
      "hosts": [
        {
          "name": "offload-streamer1",
          "hostname": "streamer1.example.com",
          "ipv6_address": ""
        },
        {
          "name": "offload-streamer2",
          "hostname": "streamer2.example.com",
          "ipv6_address": ""
        }
      ]
    }
  ]
}
Merge and apply the config? [y/n]: y

Create Load Balancing and Offload Block

Add both offload streamers as targets in a randomgroup block:

$ confcli services.routing.rules -w
Running wizard for resource 'rules'

Hint: Hitting return will set a value to its default.
Enter '?' to receive the help string

rules : [
  rule can be one of
    1: allow
    2: consistentHashing
    3: contentPopularity
    4: deny
    5: firstMatch
    6: random
    7: rawGroup
    8: rawHost
    9: split
    10: weighted
  Choose element index or name: random
  Adding a 'random' element
    rule : {
      name (default: ): balancer
      type (default: random): ⏎
      targets : [
        target (default: ): offload-streamer1
        Add another 'target' element to array 'targets'? [y/N]: y
        target (default: ): offload-streamer2
        Add another 'target' element to array 'targets'? [y/N]: ⏎
      ]
    }
  Add another 'rule' element to array 'rules'? [y/N]: ⏎
]
Generated config:
{
  "rules": [
    {
      "name": "balancer",
      "type": "random",
      "targets": [
        "offload-streamer1",
        "offload-streamer2"
      ]
    }
  ]
}
Merge and apply the config? [y/n]: y

Then create a split block with the request router and the load balanced CDN as targets:

$ confcli services.routing.rules -w
Running wizard for resource 'rules'

Hint: Hitting return will set a value to its default.
Enter '?' to receive the help string

rules : [
  rule can be one of
    1: allow
    2: consistentHashing
    3: contentPopularity
    4: deny
    5: firstMatch
    6: random
    7: rawGroup
    8: rawHost
    9: split
    10: weighted
  Choose element index or name: split
  Adding a 'split' element
    rule : {
      name (default: ): offload
      type (default: split): ⏎
      rule (default: ): in_session_group('Apple') and not in_subnet('Europe') and lt('europe_load_mbps', 1000)
      onMatch (default: ): rr1
      onMiss (default: ): balancer
    }
  Add another 'rule' element to array 'rules'? [y/N]: ⏎
]
Generated config:
{
  "rules": [
    {
      "name": "offload",
      "type": "split",
      "condition": "in_session_group('Apple') and not in_subnet('Europe') and lt('europe_load_mbps', 1000)",
      "onMatch": "rr1",
      "onMiss": "balancer"
    }
  ]
}
Merge and apply the config? [y/n]: y

The last step required is to set the entrypoint of the routing tree so the router knows where to start evaluating:

$ confcli services.routing.entrypoint offload
services.routing.entrypoint = 'offload'

Evaluate

Now that all the rules have been set up properly and the router has been reconfigured. The translated configuration can be read from the router’s configuration API:

$ curl -k https://router-host:5001/v2/configuration  2> /dev/null | jq .routing
{
  "id": "offload",
  "member_order": "sequential",
  "members": [
    {
      "host_id": "rr1",
      "id": "offload.rr1",
      "weight_function": "return ((in_session_group('Apple') ~= 0) and
                          (in_subnet('Europe') == 0) and
                          (lt('europe_load_mbps', 1000) ~= 0) and 1) or 0 "
    },
    {
      "id": "offload.balancer",
      "member_order": "weighted",
      "members": [
        {
          "host_id": "offload-streamer1",
          "id": "offload.balancer.offload-streamer1",
          "weight_function": "return 100"
        },
        {
          "host_id": "offload-streamer2",
          "id": "offload.balancer.offload-streamer2",
          "weight_function": "return 100"
        }
      ],
      "weight_function": "return 1"
    }
  ],
  "weight_function": "return 100"
}

Note that the configuration language code has been translated into its Lua equivalent.

3 - Session Groups and Classification

ESB3024 Router provides a flexible classification engine, allowing the assignment of clients into session groups that can then be used to base routing decisions on.

Session Classification

In order to perform routing it is necessary to classify incoming sessions according to the relevant parameters. This is done through session groups and their associated classifiers.

There are different ways of classifying a request:

• Strings with wildcards: Simple case-insensitive string pattern with support for adding asterisks (’*’) in order to match any value at that point in the pattern.
• String with regular expressions: A complex string matching pattern capable of matching more complicated strings than the simple wildcard matching type.

Valid string matching sources are content_url_path, content_url_query_parameters, hostname and user_agent, examples of which will be shown below.

• GeoIP: Based on the geographic location of the client, supporting wildcard matching. Geographic location data is provided by MaxMind. The possible values to match with are any combinations of:
  • Continent
  • Country
  • Cities
  • ASN
• Anonymous IP: Classifies clients using an anonymous IP. Database of anonymous IPs is provided by MaxMind.
• IP range: Based on whether a client’s IP belongs to any of the listed IP ranges or not.
• Subnet: Tests if a client’s IP belongs to a named subnet, see Subnets for more details.
• ASN ID list: Checks to see if a client’s IP belongs to any of the specified ASN IDs.
• Random: Randomly classifies clients according to a given probability. The classifier is deterministic, meaning that a session will always get the same classification, even if evaluated multiple times.

A session group may have more than one classifier. If it does, all the classifiers must match the incoming client request for it to belong to the session group. It is also possible for a request to belong to multiple session groups, or to none.

To send certain clients to a specific host you first need to create a suitable classifier using confcli in wizard mode. The wizard will guide you through the process of creating a new entry, asking you what value to input for each field and helping you by telling you what inputs are allowed for restricted fields such as the string comparison source mentioned above:

• GeoIP
• IP Range
• Wildcard pattern
• Regular expression
• Subnet
• Host name
• Content URL path
• Content URL query parameters
• User Agent
• ASN IDs
• Random
• Anonymous IP

$ confcli services.routing.classifiers -w
Running wizard for resource 'classifiers'

Hint: Hitting return will set a value to its default.
Enter '?' to receive the help string

classifiers : [
  classifier can be one of
    1: anonymousIp
    2: asnIds
    3: contentUrlPath
    4: contentUrlQueryParameters
    5: geoip
    6: hostName
    7: ipranges
    8: random
    9: regexMatcher
    10: stringMatcher
    11: subnet
    12: userAgent
  Choose element index or name: geoip
  Adding a 'geoip' element
    classifier : {
      name (default: ): sweden_matcher
      type (default: geoip): ⏎
      inverted (default: False): ⏎
      continent (default: ): ⏎
      country (default: ): sweden
      cities : [
        city (default: ): ⏎
        Add another 'city' element to array 'cities'? [y/N]: ⏎
      ]
      asn (default: ): ⏎
    }
  Add another 'classifier' element to array 'classifiers'? [y/N]: ⏎
]
Generated config:
{
  "classifiers": [
    {
      "name": "sweden_matcher",
      "type": "geoip",
      "inverted": false,
      "continent": "",
      "country": "sweden",
      "cities": [
        ""
      ],
      "asn": ""
    }
  ]
}
Merge and apply the config? [y/n]: y

$ confcli services.routing.classifiers -w
Running wizard for resource 'classifiers'

Hint: Hitting return will set a value to its default.
Enter '?' to receive the help string

classifiers : [
  classifier can be one of
    1: anonymousIp
    2: asnIds
    3: contentUrlPath
    4: contentUrlQueryParameters
    5: geoip
    6: hostName
    7: ipranges
    8: random
    9: regexMatcher
    10: stringMatcher
    11: subnet
    12: userAgent
  Choose element index or name: ipranges
  Adding a 'ipranges' element
    classifier : {
      name (default: ): company_matcher
      type (default: ipranges): ⏎
      inverted (default: False): ⏎
      ipranges : [
        iprange (default: ): 90.128.0.0/12
        Add another 'iprange' element to array 'ipranges'? [y/N]: ⏎
      ]
    }
  Add another 'classifier' element to array 'classifiers'? [y/N]: ⏎
]
Generated config:
{
  "classifiers": [
    {
      "name": "company_matcher",
      "type": "ipranges",
      "inverted": false,
      "ipranges": [
        "90.128.0.0/12"
      ]
    }
  ]
}
Merge and apply the config? [y/n]: y
  

$ confcli services.routing.classifiers -w
Running wizard for resource 'classifiers'

Hint: Hitting return will set a value to its default.
Enter '?' to receive the help string

classifiers : [
  classifier can be one of
    1: anonymousIp
    2: asnIds
    3: contentUrlPath
    4: contentUrlQueryParameters
    5: geoip
    6: hostName
    7: ipranges
    8: random
    9: regexMatcher
    10: stringMatcher
    11: subnet
    12: userAgent
  Choose element index or name: stringMatcher
  Adding a 'stringMatcher' element
    classifier : {
      name (default: ): apple_matcher
      type (default: stringMatcher): ⏎
      inverted (default: False): ⏎
      source (default: content_url_path): user_agent
      pattern (default: ): *apple*
    }
  Add another 'classifier' element to array 'classifiers'? [y/N]: ⏎
]
Generated config:
{
  "classifiers": [
    {
      "name": "apple_matcher",
      "type": "stringMatcher",
      "inverted": false,
      "source": "user_agent",
      "pattern": "*apple*"
    }
  ]
}
Merge and apply the config? [y/n]: y
  

$ confcli services.routing.classifiers -w
Running wizard for resource 'classifiers'

Hint: Hitting return will set a value to its default.
Enter '?' to receive the help string

classifiers : [
  classifier can be one of
    1: anonymousIp
    2: asnIds
    3: contentUrlPath
    4: contentUrlQueryParameters
    5: geoip
    6: hostName
    7: ipranges
    8: random
    9: regexMatcher
    10: stringMatcher
    11: subnet
    12: userAgent
  Choose element index or name: regexMatcher
  Adding a 'regexMatcher' element
    classifier : {
      name (default: ): content_matcher
      type (default: regexMatcher): ⏎
      inverted (default: False): ⏎
      source (default: content_url_path): ⏎
      pattern (default: ): .*/(live|news_channel)/.*m3u8
    }
  Add another 'classifier' element to array 'classifiers'? [y/N]: ⏎
]
Generated config:
{
  "classifiers": [
    {
      "name": "content_matcher",
      "type": "regexMatcher",
      "inverted": false,
      "source": "content_url_path",
      "pattern": ".*/(live|news_channel)/.*m3u8"
    }
  ]
}
Merge and apply the config? [y/n]: y
  

$ confcli services.routing.classifiers -w
Running wizard for resource 'classifiers'

Hint: Hitting return will set a value to its default.
Enter '?' to receive the help string

classifiers : [
  classifier can be one of
    1: anonymousIp
    2: asnIds
    3: contentUrlPath
    4: contentUrlQueryParameters
    5: geoip
    6: hostName
    7: ipranges
    8: random
    9: regexMatcher
    10: stringMatcher
    11: subnet
    12: userAgent
  Choose element index or name: subnet
  Adding a 'subnet' element
    classifier : {
      name (default: ): company_matcher
      type (default: subnet): ⏎
      inverted (default: False): ⏎
      pattern (default: ): company
    }
  Add another 'classifier' element to array 'classifiers'? [y/N]: ⏎
]
Generated config:
{
  "classifiers": [
    {
      "name": "company_matcher",
      "type": "subnet",
      "inverted": false,
      "pattern": "company"
    }
  ]
}
Merge and apply the config? [y/n]: y
  

$ confcli services.routing.classifiers -w
Running wizard for resource 'classifiers'

Hint: Hitting return will set a value to its default.
Enter '?' to receive the help string

classifiers : [
  classifier can be one of
    1: anonymousIp
    2: asnIds
    3: contentUrlPath
    4: contentUrlQueryParameters
    5: geoip
    6: hostName
    7: ipranges
    8: random
    9: regexMatcher
    10: stringMatcher
    11: subnet
    12: userAgent
  Choose element index or name: hostName
  Adding a 'hostName' element
    classifier : {
      name (default: ): host_name_classifier
      type (default: hostName): ⏎
      inverted (default: False): ⏎
      patternType (default: stringMatch): ⏎
      pattern (default: ): *live.example*
    }
  Add another 'classifier' element to array 'classifiers'? [y/N]: n
]
Generated config:
{
  "classifiers": [
    {
      "name": "host_name_classifier",
      "type": "hostName",
      "inverted": false,
      "patternType": "stringMatch",
      "pattern": "*live.example*"
    }
  ]
}
Merge and apply the config? [y/n]: y
  

$ confcli services.routing.classifiers -w
Running wizard for resource 'classifiers'

Hint: Hitting return will set a value to its default.
Enter '?' to receive the help string

classifiers : [
  classifier can be one of
    1: anonymousIp
    2: asnIds
    3: contentUrlPath
    4: contentUrlQueryParameters
    5: geoip
    6: hostName
    7: ipranges
    8: random
    9: regexMatcher
    10: stringMatcher
    11: subnet
    12: userAgent
  Choose element index or name: contentUrlPath
  Adding a 'contentUrlPath' element
    classifier : {
      name (default: ): vod_matcher
      type (default: contentUrlPath): ⏎
      inverted (default: False): ⏎
      patternType (default: stringMatch): ⏎
      pattern (default: ): *vod*
    }
  Add another 'classifier' element to array 'classifiers'? [y/N]: n
]
Generated config:
{
  "classifiers": [
    {
      "name": "vod_matcher",
      "type": "contentUrlPath",
      "inverted": false,
      "patternType": "stringMatch",
      "pattern": "*vod*"
    }
  ]
}
Merge and apply the config? [y/n]: y
  

$ confcli services.routing.classifiers -w
Running wizard for resource 'classifiers'

Hint: Hitting return will set a value to its default.
Enter '?' to receive the help string

classifiers : [
  classifier can be one of
    1: anonymousIp
    2: asnIds
    3: contentUrlPath
    4: contentUrlQueryParameters
    5: geoip
    6: hostName
    7: ipranges
    8: random
    9: regexMatcher
    10: stringMatcher
    11: subnet
    12: userAgent
  Choose element index or name: contentUrlQueryParameters
  Adding a 'contentUrlQueryParameters' element
    classifier : {
      name (default: ): bitrate_matcher
      type (default: contentUrlQueryParameters): ⏎
      inverted (default: False): ⏎
      patternType (default: stringMatch): regex
      pattern (default: ): .*bitrate=100000.*
    }
  Add another 'classifier' element to array 'classifiers'? [y/N]: n
]
Generated config:
{
  "classifiers": [
    {
      "name": "bitrate_matcher",
      "type": "contentUrlQueryParameters",
      "inverted": false,
      "patternType": "regex",
      "pattern": ".*bitrate=100000.*"
    }
  ]
}
Merge and apply the config? [y/n]: y
  

$ confcli services.routing.classifiers -w
Running wizard for resource 'classifiers'

Hint: Hitting return will set a value to its default.
Enter '?' to receive the help string

classifiers : [
  classifier can be one of
    1: anonymousIp
    2: asnIds
    3: contentUrlPath
    4: contentUrlQueryParameters
    5: geoip
    6: hostName
    7: ipranges
    8: random
    9: regexMatcher
    10: stringMatcher
    11: subnet
    12: userAgent
  Choose element index or name: userAgent
  Adding a 'userAgent' element
    classifier : {
      name (default: ): iphone_matcher
      type (default: userAgent): ⏎
      inverted (default: False): ⏎
      patternType (default: stringMatch): regex
      pattern (default: ): i(P|p)hone
    }
  Add another 'classifier' element to array 'classifiers'? [y/N]: n
]
Generated config:
{
  "classifiers": [
    {
      "name": "iphone_matcher",
      "type": "userAgent",
      "inverted": false,
      "patternType": "regex",
      "pattern": "i(P|p)hone"
    }
  ]
}
Merge and apply the config? [y/n]: y
  

$ confcli services.routing.classifiers -w
Running wizard for resource 'classifiers'

Hint: Hitting return will set a value to its default.
Enter '?' to receive the help string

classifiers : [
  classifier can be one of
    1: anonymousIp
    2: asnIds
    3: contentUrlPath
    4: contentUrlQueryParameters
    5: geoip
    6: hostName
    7: ipranges
    8: random
    9: regexMatcher
    10: stringMatcher
    11: subnet
    12: userAgent
  Choose element index or name: asnIds
  Adding a 'asnIds' element
    classifier : {
      name (default: ): asn_matcher
      type (default: asnIds): ⏎
      inverted (default: False): ⏎
      asnIds <The list of ASN IDs to accept. (default: [])>: [
        asnId: 1
        Add another 'asnId' element to array 'asnIds'? [y/N]: y
        asnId: 2
        Add another 'asnId' element to array 'asnIds'? [y/N]: y
        asnId: 3
        Add another 'asnId' element to array 'asnIds'? [y/N]: ⏎
      ]
    }
  Add another 'classifier' element to array 'classifiers'? [y/N]: ⏎
]
Generated config:
{
  "classifiers": [
    {
      "name": "asn_matcher",
      "type": "asnIds",
      "inverted": false,
      "asnIds": [
        1,
        2,
        3
      ]
    }
  ]
}
Merge and apply the config? [y/n]: y
  

$ confcli services.routing.classifiers -w
Running wizard for resource 'classifiers'

Hint: Hitting return will set a value to its default.
Enter '?' to receive the help string

classifiers : [
  classifier can be one of
    1: anonymousIp
    2: asnIds
    3: contentUrlPath
    4: contentUrlQueryParameters
    5: geoip
    6: hostName
    7: ipranges
    8: random
    9: regexMatcher
    10: stringMatcher
    11: subnet
    12: userAgent
  Choose element index or name: random
  Adding a 'random' element
    classifier <A classifier randomly applying to clients based on the provided probability. (default: OrderedDict())>: {
      name (default: ): random_matcher
      type (default: random):
      probability (default: 0.5): 0.7
    }
  Add another 'classifier' element to array 'classifiers'? [y/N]: n
]
Generated config:
{
  "classifiers": [
    {
      "name": "random_matcher",
      "type": "random",
      "probability": 0.7
    }
  ]
}
Merge and apply the config? [y/n]: y
  

$ confcli services.routing.classifiers -w
Running wizard for resource 'classifiers'

Hint: Hitting return will set a value to its default.
Enter '?' to receive the help string

classifiers : [
  classifier can be one of
    1: anonymousIp
    2: asnIds
    3: contentUrlPath
    4: contentUrlQueryParameters
    5: geoip
    6: hostName
    7: ipranges
    8: random
    9: regexMatcher
    10: stringMatcher
    11: subnet
    12: userAgent
  Choose element index or name: anonymousIp
  Adding a 'anonymousIp' element
    classifier : {
      name (default: ): anon_ip_matcher
      type (default: anonymousIp):
      inverted (default: False):
    }
  Add another 'classifier' element to array 'classifiers'? [y/N]: n
]
Generated config:
{
  "classifiers": [
    {
      "name": "anon_ip_matcher",
      "type": "anonymousIp",
      "inverted": false
    }
  ]
}
Merge and apply the config? [y/n]: y
  

These classifiers can now be used to construct session groups and properly classify clients. Using the examples above, let’s create a session group classifying clients from Sweden using an Apple device:

$ confcli services.routing.sessionGroups -w
Running wizard for resource 'sessionGroups'

Hint: Hitting return will set a value to its default.
Enter '?' to receive the help string

sessionGroups : [
  sessionGroup : {
    name (default: ): inSwedenUsingAppleDevice
    classifiers : [
      classifier (default: ): sweden_matcher
      Add another 'classifier' element to array 'classifiers'? [y/N]: y
      classifier (default: ): apple_matcher
      Add another 'classifier' element to array 'classifiers'? [y/N]: ⏎
    ]
  }
  Add another 'sessionGroup' element to array 'sessionGroups'? [y/N]: ⏎
]
Generated config:
{
  "sessionGroups": [
    {
      "name": "inSwedenUsingAppleDevice",
      "classifiers": [
        "sweden_matcher",
        "apple_matcher"
      ]
    }
  ]
}
Merge and apply the config? [y/n]: y

Clients classified by the sweden_matcher and apple_matcher classifiers will now be put in the session group inSwedenUsingAppleDevice. Using session groups in routing will be demonstrated later in this document.

Advanced Classification

The above example will simply apply all classifiers in the list, and as long as they all evaluate to true for a session, that session will be tagged with the session group. For situations where this isn’t enough, classifiers can instead be combined using simple logic statements to form complex rules.

A first simple example can be a session group that accepts any viewers in either ASN 1, 2 or 3 (corresponding to the classifier asn_matcher or living in Sweden. This can be done by creating a session group, and adding the following logic statement:

'sweden_matcher' OR 'asn_matcher'

A slightly more advanced case is where a session group should only contain sessions neither in any of the three ASNs nor in Sweden. This is done by negating the previous example:

NOT ('sweden_matcher' OR 'asn_matcher')

A single classifier can also be negated, rather than the whole statement, for example to accept any Swedish viewers except those in the three ASNs:

'sweden_matcher' AND NOT 'asn_matcher'

Arbitrarily complex statements can be created using classifier names, parentheses, and the keywords AND, OR and NOT.

For example a session group accepting any Swedish viewers except those in the Stockholm region unless they are also Apple users:

'sweden_matcher' AND (NOT 'stockholm_matcher' OR 'apple_matcher')

Note that the classifier names must be enclosed in single quotes when using this syntax.

Applying this kind of complex classifier using confcli is no more difficult than adding a single classifier at a time:

• Boolean Classifiers

$ confcli services.routing.sessionGroups. -w
Running wizard for resource 'sessionGroups'

Hint: Hitting return will set a value to its default.
Enter '?' to receive the help string

sessionGroups : [
  sessionGroup : {
    name (default: ): complex_group
    classifiers : [
      classifier (default: ): 'sweden_matcher' AND (NOT 'stockholm_matcher' OR 'apple_matcher')
      Add another 'classifier' element to array 'classifiers'? [y/N]: ⏎
    ]
  }
  Add another 'sessionGroup' element to array 'sessionGroups'? [y/N]: ⏎
]
Generated config:
{
  "sessionGroups": [
    {
      "name": "complex_group",
      "classifiers": [
        "'sweden_matcher' AND (NOT 'stockholm_matcher' OR 'apple_matcher')"
      ]
    }
  ]
}
Merge and apply the config? [y/n]: y
  

4 - Advanced features

4.1 - Content popularity

ESB3024 Router allows routing decisions based on content popularity. All incoming content requests are tracked to continuously update a content popularity ranking list. The popularity ranking algorithm is designed to let popular content quickly rise to the top while unpopular content decays and sinks towards the bottom.

Configuration

All configuration parameters for content popularity reside in the settings object of the configuration, an example of which can be seen below:

{
  "settings": {
    "content_popularity": {
      "algorithm": "scored_based",
      "session_group_names": ["vod_only"],
      "score_based:": {
        "requests_between_popularity_decay": 1000,
        "popularity_list_max_size": 100000,
        "popularity_prediction_factor": 2.5,
        "popularity_decay_fraction": 0.2
      },
      "time_based": {
        "intervals_per_hour": 10
      }
    }
  }
}

The field algorithm dictates which content popularity tracking algorithm to use, can either be score_based or time_based.

The field session_group_names defines the sessions for which content popularity should be tracked. In the example above, session belonging to the vod_only session group will be tracked for content popularity. If left empty, content popularity will be tracked for all sessions.

The remaining configuration parameters are algorithm specific.

Score based algorithm

The field popularity_list_max_size defines the maximum amount of unique contents to track for popularity. This can be used to limit memory growth. A single entry in the popularity ranking list will at most consume 180 B of memory, giving an upper bound memory growth of \(180n_{\text{requests}}\) bytes. E.g. using "popularity_list_max_size": 1000 would consume at most 180⋅1,000 = 180,000 B = 0.18 MB. If the content popularity list is full, a request to unique content would replace the least popular content.

Setting a very high max size won’t impact performance, it will only consume more memory.

The field requests_between_popularity_decay defines the number of requests between each popularity decay update, an integral component of this feature.

The fields popularity_prediction_factor and popularity_decay_fraction tune the behaviour of the content popularity ranking algorithm, explained further below.

Decay update

To allow for popular content to quickly rise in popularity and unpopular content to sink, a dynamic popularity ranking algorithm is used. The goal of the algorithm is to track content popularity in real time, allowing routing decisions based on the requested content’s popularity. The algorithm is applied every decay update.

The algorithm uses current trending content to predict content popularity. The field popularity_prediction_factor regulates how much the algorithm should rely on predicted popularity. A high prediction factor allows rising content to quickly rise to high popularity but can also cause unpopular content with a sudden burst of requests to wrongfully rise to the top. A low prediction factor can cause stagnation in the popularity ranking, not allowing new popular content to rise to the top.

Unpopular content decays in popularity, the magnitude of which is regulated by popularity_decay_fraction. A high value will aggressively decay content popularity every decay update while a low value will bloat the ranking, causing stagnation. Once content decays to a trivially low popularity score, it is pruned from the content popularity list.

When configuring these tuning parameters, the most crucial data to consider is the size of your asset catalog, i.e. the number of unique contents you offer. The recommended values, obtained through testing, are presented in the table below. Note that the field popularity_prediction_factor is the principal factor in controlling the algorithm’s behaviour.

Time based algorithm

The time based algorithm only requires the configuration parameter intervals_per_hour. E.g., the value "intervals_per_hour": 10 would give 10 six minute intervals per hour. During each interval, all unique content requests has an associated counter, increasing by one for each incoming request. After an hour, all intervals have been cycled through. The counters in the first interval will be reset and all incoming content requests will increase the counters in the first interval again. This cycle continues forever.

When determining a single content’s popularity, the sum of each content’s counter in all intervals is used to determine a popularity ranking.

Usage in routing

Content popularity ranking is available in Lua through the simple member session.content_global_popularity, returning the requested content’s popularity ranking. E.g., the routing configuration below will route all requests to content with a popularity ranking lower than 10, i.e. top 10 most popular content, to the host edge-streamer while requests to content outside of the top 10 most popular will be routed to the host offload.

"routing": {
  "id": "routing_table",
  "member_order": "sequential",
  "members": [
    {
      "id": "edge",
      "weight_function": "return session.content_global_popularity < 11 and 1 or 0",
      "host_id": "edge-streamer"
    },
    {
      "id": "offload",
      "weight_function": "return 1",
      "host_id": "offload"
    }
  ]
}

4.2 - Consistent Hashing

Consistent hashing based routing is a feature that can be used to distribute requests to a set of hosts in a cache friendly manner. By using Agile Content’s consistent distributed hash algorithm, the amount of cache redistribution is minimized within a set of hosts. Requests for a content will always be routed to the same set of hosts, the amount of which is configured by the spread factor, allowing high cache usage. When adding or removing hosts, the algorithm minimizes cache redistribution.

Say you have the host group [s1, s2, s3, s4, s5] and have configured spreadFactor = 3. A request for a content asset1 would then be routed to the same three hosts with one of them being selected randomly for each request. Requests for a different content asset2 would also be routed to one of three different hosts, most likely a different combination of hosts than requests for content asset1.

Example routing results with spreadFactor = 3:

• Request for asset1 → route to one of [s1, s3, s4].
• Request for asset2 → route to one of [s2, s4, s5].
• Request for asset3 → route to one of [s1, s2, s5].

Since consistent hashing based routing ensures that requests for a specific content always get routed to the same set of hosts, the risk of cache misses are lowered on the hosts since they will be served the same content requests over and over again.

Note that the maximum value of spreadFactor is 64. Consequently, the highest amount of hosts you can use in a consistentHashing rule block is 64.

Three different hashing algorithms are available: MD5, SDBM and Murmur. The algorithm is chosen during configuration.

Configuration

Configuring consistent hashing based routing is easily done using confcli. Let’s configure the example described above:

confcli services.routing.rules -w
Running wizard for resource 'rules'

Hint: Hitting return will set a value to its default.
Enter '?' to receive the help string

rules : [
  rule can be one of
    1: allow
    2: consistentHashing
    3: contentPopularity
    4: deny
    5: firstMatch
    6: random
    7: rawGroup
    8: rawHost
    9: split
    10: weighted
  Choose element index or name: consistentHashing
  Adding a 'consistentHashing' element
    rule : {
      name (default: ): consistentHashingRule 
      type (default: consistentHashing): 
      spreadFactor (default: 1): 3
      hashAlgorithm (default: MD5):
      targets : [
        target : {
          target (default: ): s1
          enabled (default: True): 
        }
        Add another 'target' element to array 'targets'? [y/N]: y
        target : {
          target (default: ): s2
          enabled (default: True): 
        }
        Add another 'target' element to array 'targets'? [y/N]: y
        target : {
          target (default: ): s3
          enabled (default: True): 
        }
        Add another 'target' element to array 'targets'? [y/N]: y
        target : {
          target (default: ): s4
          enabled (default: True): 
        }
        Add another 'target' element to array 'targets'? [y/N]: y
        target : {
          target (default: ): s5
          enabled (default: True): 
        }
        Add another 'target' element to array 'targets'? [y/N]: n
      ]
    }
  Add another 'rule' element to array 'rules'? [y/N]: n
]
Generated config:
{
  "rules": [
    {
      "name": "consistentHashingRule",
      "type": "consistentHashing",
      "spreadFactor": 3,
      "hashAlgorithm": "MD5",
      "targets": [
        {
          "target": "s1",
          "enabled": true
        },
        {
          "target": "s2",
          "enabled": true
        },
        {
          "target": "s3",
          "enabled": true
        },
        {
          "target": "s4",
          "enabled": true
        },
        {
          "target": "s5",
          "enabled": true
        }
      ]
    }
  ]
}

Adding hosts

Adding a host to the list will give an additional target for the consistent hashing algorithm to route requests to. This will shift content distribution onto the new host.

confcli services.routing.rules.consistentHashingRule.targets -w
Running wizard for resource 'targets'

Hint: Hitting return will set a value to its default.
Enter '?' to receive the help string

targets : [
  target : {
    target (default: ): s6
    enabled (default: True): 
  }
  Add another 'target' element to array 'targets'? [y/N]: n
]
Generated config:
{
  "targets": [
    {
      "target": "s6",
      "enabled": true
    }
  ]
}
Merge and apply the config? [y/n]: y

Removing hosts

There is one very important caveat of using a consistent hashing rule block. As long as you don’t modify the list of hosts, the consistent hashing algorithm will keep routing requests to the same hosts. However, if you remove a host from the block in any position except the last, the consistent hashing algorithm’s behaviour will change and the algorithm cannot maintain a minimum amount of cache redistribution.

If you’re in a situation where you have to remove a host from the routing targets but want to keep the same consistent hashing behaviour, e.g. during very high load, you’ll have to toggle that target’s enabled field to false. E.g., disabling requests to s2 can be accomplished by:

$ confcli services.routing.rules.consistentHashingRule.targets.1.enabled false
services.routing.rules.consistentHashingRule.targets.1.enabled = False
$ confcli services.routing.rules.consistentHashingRule.targets.1
{
    "1": {
        "target": "s2",
        "enabled": false
    }
}

If you modify the list order or remove hosts, it is highly recommended to do so during moments where a higher rate of cache misses are acceptable.

4.3 - Predictive load balancing

Why use predictive load balancing?

Predictive load balancing is a tool that can be used to avoid overloading hosts with traffic. Consider the case where a popular event starts at a certain time, let’s say 12 PM. A spike in traffic will be routed to the hosts that are streaming the content at 12 PM, most of them starting at low bitrates. A host might have sufficient bandwidth left to take on more clients but when the recently connected clients start ramping up in video quality and increase their bitrate, the host can quickly become overloaded, possibly dropping incoming requests or going offline. Predictive load balancing solves this issue by considering how many times a host recently been redirected to.

Basic configuration

The router allows predicting incoming load for individual hosts. Through the use of the selection input API, the routing engine can predict incoming load by tracking recent host selections and make routing decisions accordingly.

What is considered recent is configurable and defaults to 500 milliseconds:

• confcli
• JSON

$ confcli services.routing.tuning.target.recentDurationMilliseconds
{
    "recentDurationMilliseconds": 500
}
$ confcli services.routing.tuning.target.recentDurationMilliseconds 1000
services.routing.tuning.target.recentDurationMilliseconds = 1000

{
  "tuning": {
    "target_recent_duration_milliseconds": 500
  }
}

How to use predictive load balancing

The standard Lua library provides four functions for predictive load balancing that can be used when constructing conditions/weight functions: host_bitrate() , host_bitrate_custom(), host_has_bw() and host_has_bw_custom(). All require data to be supplied to the selection input API and apply only to leaf nodes in the routing tree. In order for predictive load balancing to work properly the data must be updated at regular intervals. The data needs to be supplied by the target system.

These functions are suitable to used as host health checks. To configure host health checks, see configuring CDNs and hosts.

Note that host_bitrate() and host_has_bw() rely on data supplied by metrics agents, detailed in Cache hardware metrics: monitoring and routing.

host_bitrate_custom() and host_has_bw_custom() rely on manually supplied selection input data, detailed in selection input API. The bitrate unit depends on the data submitted to the selection input API.

host_bitrate()

host_bitrate() returns the predicted bitrate (in megabits per second) of the host after the recently connected clients start ramping up in streaming quality. The function accepts up to four arguments:

• interface: The name of the interface to use for bitrate prediction.
• Optional avg_bitrate: the average bitrate per client, defaults to 6 megabits per second.
• Optional num_routers: the number of routers that can route to this host, defaults to 1. This is important to accurately predict the incoming load if multiple routers are used.
• Optional host: The name of the host to use for bitrate prediction. Defaults to the current host if not provided.

Examples of usage:

host_bitrate({interface="eths0"})
host_bitrate({avg_bitrate=1, interface="eths0"})
host_bitrate({num_routers=2, interface="eths0"})
host_bitrate({avg_bitrate=1, num_routers=4, interface="eths0"})
host_bitrate({avg_bitrate=1, num_routers=4, host="custom_host", interface="eths0"})

host_bitrate() calculates the predicted bitrate as:

predicted_host_bitrate = current_host_bitrate + (recent_connections * avg_bitrate * num_routers)

host_bitrate_custom()

Same functionality as host_bitrate() but uses a custom selection input variable as bitrate input instead of accessing hardware metrics. The function accepts up to three arguments:

• custom_bitrate_var: The name of the selection input variable to be used for accessing current host bitrate.
• Optional avg_bitrate: see host_bitrate() documentation above.
• Optional num_routers: see host_bitrate() documentation above.

host_bitrate_custom({custom_bitrate_var="host1_current_bitrate"})
host_bitrate_custom({avg_bitrate=1, custom_bitrate_var="host1_current_bitrate"})
host_bitrate_custom({num_routers=4, custom_bitrate_var="host1_current_bitrate"})

host_has_bw()

Instead of accessing the predicted bitrate of a host through host_bitrate(), host_has_bw() returns 1 if the host is predicted to have enough bandwidth left to take on more clients after recent connections ramp up in bitrate, otherwise it returns 0. The function accepts up to five arguments:

• interface: see host_bitrate() documentation above.
• Optional avg_bitrate: see host_bitrate() documentation above.
• Optional num_routers: see host_bitrate() documentation above.
• Optional host: see host_bitrate() documentation above.
• Optional margin: the bitrate (megabits per second) headroom that should be taken into account during calculation, defaults to 0.

host_has_bw() returns whether or not the following statement is true:

predicted_host_bitrate + margin < host_bitrate_capacity

Examples of usage:

host_has_bw({interface="eths0"})
host_has_bw({margin=10, interface="eth0"})
host_has_bw({avg_bitrate=1, interface="eth0"})
host_has_bw({num_routers=4, interface="eth0"})
host_has_bw({host="custom_host", interface="eth0"})

host_has_bw_custom()

Same functionality as host_has_bw() but uses a custom selection input variable as bitrate and capacity input. The function accepts up to five arguments:

• custom_capacity_var: the name of the selection input variable to be used for accessing host capacity.
• custom_bitrate_var: see host_bitrate_custom() documentation
• Optional margin: see host_has_bw() documentation above. above.
• Optional avg_bitrate: see host_bitrate() documentation above.
• Optional num_routers: see host_bitrate() documentation above.

Examples of usage:

host_has_bw_custom({custom_capacity_var="host1_capacity", custom_bitrate_var="host1_current_bitrate"})
host_has_bw_custom({margin=10, custom_capacity_var="host1_capacity", custom_bitrate_var="host1_current_bitrate"})
host_has_bw_custom({avg_bitrate=1, custom_capacity_var="host1_capacity", custom_bitrate_var="host1_current_bitrate"})
host_has_bw_custom({num_routers=4, custom_capacity_var="host1_capacity", custom_bitrate_var="host1_current_bitrate"})

Examples in routing

When using confcli it’s not recommended to use host_bitrate() since it’s not possible to make comparisons using <, > or similar operators. Using host_has_bw() makes it easy to construct conditions utilizing predictive load balancing.

host_has_bw() and host_has_bw_custom() are excellent candidates to be used as health check functions for hosts, see configuring CDNs and hosts for more details.

• confcli
• JSON

$ confcli services.routing.rules -w
Running wizard for resource 'rules'

Hint: Hitting return will set a value to its default.
Enter '?' to receive the help string

rules : [
  rule can be one of
    1: allow
    2: consistentHashing
    3: contentPopularity
    4: deny
    5: firstMatch
    6: random
    7: rawGroup
    8: rawHost
    9: split
    10: weighted
  Choose element index or name: weighted
  Adding a 'weighted' element
    rule : {
      name (default: ): weighted_and_has_bw
      type (default: weighted):
      targets : [
        target : {
          target (default: ): host1
          weight (default: 100):
          condition (default: always()): host_has_bw({interface="eths0"})
        }
        Add another 'target' element to array 'targets'? [y/N]: y
        target : {
          target (default: ): host2
          weight (default: 100): 100
          condition (default: always()): host_has_bw({margin=1000, interface="eths0"})
        }
        Add another 'target' element to array 'targets'? [y/N]: y
        target : {
          target (default: ): host3
          weight (default: 100):
          condition (default: always()): host_has_bw({avg_bitrate=1, num_routers=2, margin=5000, interface="eths0"})
        }
        Add another 'target' element to array 'targets'? [y/N]: n
      ]
    }
  Add another 'rule' element to array 'rules'? [y/N]: n
]
Generated config:
{
  "rules": [
    {
      "name": "weighted_and_has_bw",
      "type": "weighted",
      "targets": [
        {
          "target": "host1",
          "weight": "100",
          "condition": "host_has_bw({interface="eths0"})"
        },
        {
          "target": "host2",
          "weight": "100",
          "condition": "host_has_bw({margin=1000, interface="eths0"})"
        },
        {
          "target": "host3",
          "weight": "100",
          "condition": "host_has_bw({avg_bitrate=1, num_routers=2, margin=5000, interface="eths0"})"
        }
      ]
    }
  ]
}

"routing": {
  "id": "weighted_and_has_bw",
  "member_order": "sorted",
  "members": [
    {
      "id": "1",
      "host_id": "host1",
      "weight_function": "return host_bitrate({interface="eths0"}) > 0 and 1 or 0"
    },
    {
      "id": "2",
      "host_id": "host2",
      "weight_function": "return host_bitrate({avg_bitrate=1, interface="eths0"}) > 10000 and 1 or 0"
    },
    {
      "id": "3",
      "host_id": "host3",
      "weight_function": "return host_has_bw({avg_bitrate=1, num_routers=2, margin=5000, interface="eths0"}) and 1 or 0"
    }
  ],
  "weight_function": "return 1"
}

4.4 - Security token verification

The security token verification feature allows for ESB3024 Router to only process requests that contain a correct security token. The token is generated by the client, for example in the portal, using an algorithm that it shares with the router. The router verifies the token and rejects the request if the token is incorrect.

It is beyond the scope of this document to describe how the token is generated, that is described in the Security Tokens application note that is installed with the ESB3024 Router’s extra documentation.

Setting up a routing rule

The token verification is performed by calling the verify_security_token() function from a routing rule. The function returns 1 if the token is correct, otherwise it returns 0. It should typically be called from the first routing rule, to make requests with bad tokens fail as early as possible.

The confcli example assumes that the router already has rules configured, with an entry point named select_cdn. Token verification is enabled by inserting an “allow” rule first in the rule list.

• confcli
• JSON

confcli services.routing.rules -w
Running wizard for resource 'rules'

Hint: Hitting return will set a value to its default.
Enter '?' to receive the help string

rules : [
  rule can be one of
    1: allow
    2: consistentHashing
    3: contentPopularity
    4: deny
    5: firstMatch
    6: random
    7: rawGroup
    8: rawHost
    9: split
    10: weighted
  Choose element index or name: allow
  Adding a 'allow' element
    rule : {
      name (default: ): token_verification
      type (default: allow):
      condition (default: always()): verify_security_token()
      onMatch (default: ): select_cdn
    }
  Add another 'rule' element to array 'rules'? [y/N]: n
]
Generated config:
{
  "rules": [
    {
      "name": "token_verification",
      "type": "allow",
      "condition": "verify_security_token()",
      "onMatch": "select_cdn"
    }
  ]
}
Merge and apply the config? [y/n]: y

$ confcli services.routing.entrypoint token_verification
services.routing.entrypoint = 'token_verification'

"routing": {
  "id": "token_verification",
  "member_order": "sequential",
  "members": [
    {
      "id": "token_verification.0.select_cdn",
      "member_order": "weighted",
      "members": [
        ...
      ],
      "weight_function": "return verify_security_token() ~= 0"
    },
    {
      "id": "token_verification.1.rejected",
      "member_order": "sequential",
      "members": [],
      "weight_function": "return 1"
    }
  ],
  "weight_function": "return 100"
},

Configuring security token options

The secret parameter is not part of the router request, but needs to be configured separately in the router. That can be done with the host-config tool that is installed with the router.

Besides configuring the secret, host-config can also configure floating sessions and a URL prefix. Floating sessions are sessions that are not tied to a specific IP address. When that is enabled, the token verification will not take the IP address into account when verifying the token.

The security token verification is configured per host, where a host is the name of the host that the request was sent to. This makes it possible for a router to support multiple customer accounts, each with their own secret. If no configuration is found for a host, a configuration with the name default is used.

host-config supports three commands: print, set and delete.

Print

The print command prints the current configuration for a host. The following parameters are supported:

host-config print [-n <host-name>]

By default it prints the configuration for all hosts, but if the optional -n flag is given it will print the configuration for a single host.

Set

The set command sets the configuration for a host. The configuration is given as command line parameters. The following parameters are supported:

host-config set
    -n <host-name>
    [-f floating]
    [-p url-prefix]
    [-r <secret-to-remove>]
    [-s <secret-to-add>]

• -n <host-name> - The name of the host to configure.
• -f floating - A boolean option that specifies if floating sessions are accepted. The parameter accepts the values true and false.
• -p url-prefix - A URL prefix that is used for identifying requests that come from a certain account. This is not used when verifying tokens.
• -r <secret-to-remove> - A secret that should be removed from the list of secrets.
• -s <secret-to-add> - A secret that should be added to the list of secrets.

For example, to set the secret “secret-1” and enable floating sessions for the default host, the following command can be used:

host-config set -n default -s secret-1 -f true

The set command only touches the configuration options that are mentioned on the command line, so the following command line will add a second secret to the default host without changing the floating session setting:

host-config set -n default -s secret-2

It is possible to set multiple secrets per host. This is useful when updating a secret, then both the old and the new secret can be valid during the transition period. After the transition period the old secret can be removed by typing:

host-config set -n default -r secret-1

Delete

The delete command deletes the configuration for a host. It supports the following parameters:

host-config delete -n <host-name>

For example, to delete the configuration for example.com, the following command can be used:

host-config delete -n example.com

Global options

host-config also has a few global options. They are:

• -k <security-key> - The security key that is used when communicating with the router. This is normally retrieved automatically.
• -h - Print a help message and exit.
• -r <router> - The router to connect to. This default to localhost, but can be changed to connect to a remote router.
• -v - Verbose output, can be given multiple times.

Debugging security token verification

The security token verification only logs messages when the log level is set to 4 or higher. Then it will only log some errors. It is possible to enable more verbose logging using the security-token-config that is installed together with the router.

When verbose logging is enabled, the router will log information about the token verification, including the configured token secrets, so it needs to be used with care.

The logged lines are prefixed with verify_security_token.

The security-token-config tool supports the commands print and set.

Print

The print command prints the current configuration. If nothing is configured it will not print anything.

Set

The set command sets the configuration. The following parameters are supported:

security-token-config set
    [-d <enabled>]

• -d <enabled> - A boolean option that specifies if debug logging should be enabled or not. The parameter accepts the values true and false.

4.5 - Subnets API

ESB3024 Router provides utilities to quickly match clients into subnets. Any combination of IPv4 and IPv6 addresses can be used. To begin, a JSON file is needed, defining all subnets, e.g:

{
  "255.255.255.255/24": "area1",
  "255.255.255.255/16": "area2",
  "255.255.255.255/8": "area3",
  "90.90.1.3/16": "area4",
  "5.5.0.4/8": "area5",
  "2a02:2e02:9bc0::/48": "area6",
  "2a02:2e02:9bc0::/32": "area7",
  "2a02:2e02:9bc0::/16": "area8",
  "2a02:2e02:9de0::/44": "combined_area",
  "2a02:2e02:ada0::/44": "combined_area"
}

and PUT it to the endpoint :5001/v1/subnets or :5001/v2/subnets, the API version doesn’t matter for subnets:

curl -k -T subnets.json -H "Content-Type: application/json" https://router-host:5001/v1/subnets

Note that it is possible for several subnet CIDR strings to share the same label, effectively grouping them together.

This will load the subnets into the router which will then be usable within any Lua functions, accessed from the request and session tables respectively, e.g.

{
  "routing": {
    "id": "routing_table",
    "member_order": "sequential",
    "members": [
      {
        "id": "node1",
        "host_id": "host1",
        "weight_function": "return request.subnet == 'area1' and 1 or 0"
      }
    ]
  }
}

Subnet matching will use the client IP fetched from the request or session tables. When possible, the subnet with the longest matching subnet mask will be chosen, i.e. 255.255.255.255/28will be chosen over 255.255.255.255/24. If no matching subnets are found, the boolean value false will be returned.

NOTE: To use booleans in strings in Lua, calling tostring(bool) is required. Therefore, since subnet lookup might return false, the subnet call should be wrapped as: tostring(session.subnet) or tostring(requst.subnet).

Invalid ip-addresses will be omitted during subnet list construction accompanied by a message in the log displaying the invalid IP address.

4.6 - Lua Features

Detailed descriptions and examples of Lua features offered by ESB3024 Router.

4.6.1 - Global Lua Tables

There are multiple global tables containing important data available while writing Lua code for the router.

selection_input

Contains arbitrary, custom fields fed into the router by clients, see API overview for details on how to inject data into this table.

Note that the selection_input table is iterable.

Usage examples:

print(selection_input['some_value'])

-- Iterate over table
if selection_input then
    for k, v in pairs(selection_input) do
        print('here is '..'selection_input!')
        print(k..'='..v)
    end
else
    print('selection_input is nil')
end

session_groups

Defines a mapping from session group name to boolean, indicating whether the session belongs to the session group or not.

Usage examples:

if session_groups.vod then print('vod') else print('not vod') end
if session_groups['vod'] then print('vod') else print('not vod') end

session_count

Provides counters of number of session types per session group. The table uses the structure qoe_score.<session_type>.<session_group>.

Usage examples:

print(session_count.instream.vod)
print(session_count.initial.vod)

qoe_score

Provides the quality of experience score per host per session group. The table uses the structure qoe_score.<host>.<session_group>.

Usage examples:

print(qoe_score.host1.vod)
print(qoe_score.host1.live)

request

Contains data related to the HTTP request between the client and the router.

• request.method
  • Description: HTTP request method.
  • Type: string
  • Example: 'GET', 'POST'
• request.body
  • Description: HTTP request body string.
  • Type: string or nil
  • Example: '{"foo": "bar"}'
• request.major_version
  • Description: Major HTTP version such as x in HTTP/x.1.
  • Type: integer
  • Example: 1
• request.minor_version
  • Description: Minor HTTP version such as x in HTTP/1.x.
  • Type: integer
  • Example: 1
• request.protocol
  • Description: Transfer protocol variant.
  • Type: string
  • Example: 'HTTP', 'HTTPS'
• request.client_ip
  • Description: IP address of the client issuing the request.
  • Type: string
  • Example: '172.16.238.128'
• request.path_with_query_params
  • Description: Full request path including query parameters.
  • Type: string
  • Example: '/mycontent/superman.m3u8?b=y&c=z&a=x'
• request.path
  • Description: Request path without query parameters.
  • Type: string
  • Example: '/mycontent/superman.m3u8'
• request.query_params
  • Description: The query parameter string.
  • Type: string
  • Example: 'b=y&c=z&a=x'
• request.filename
  • Description: The part of the path following the final slash, if any.
  • Type: string
  • Example: 'superman.m3u8'
• request.subnet
  • Description: Subnet of client_ip.
  • Type: string or nil
  • Example: 'all'