unleash.unleash/website/docs/reference/api/legacy/unleash/client/features.md

title
/api/client/features

In order to access the client API endpoints you need to identify yourself. Unless you're using the none authentication method, you'll need to create a CLIENT token and add an Authorization header using the token.

Fetching Feature Flags

GET: http://unleash.host.com/api/client/features

HEADERS:

• UNLEASH-APPNAME: appName
• UNLEASH-INSTANCEID: instanceId

This endpoint is the one all clients should use to fetch all available feature flags from the unleash-server. The response returns all active feature flags and their current strategy configuration. A feature flag will have at least one configured strategy. A strategy will have a name and parameters map.

Note: Clients should prefer the strategies property. Legacy properties (strategy & parameters) will be kept until version 2 of the format.

This endpoint should never return anything besides a valid 20X or 304-response. It will also include an Etag-header. The value of this header can be used by clients as the value of the If-None-Match-header in the request to prevent a data transfer if the client already has the latest response locally.

Example response:

{
  "version": 1,
  "features": [
    {
      "name": "Feature.A",
      "type": "release",
      "enabled": false,
      "stale": false,
      "strategies": [
        {
          "name": "default",
          "parameters": {}
        }
      ],
      "strategy": "default",
      "parameters": {}
    },
    {
      "name": "Feature.B",
      "type": "killswitch",
      "enabled": true,
      "stale": false,
      "strategies": [
        {
          "name": "ActiveForUserWithId",
          "parameters": {
            "userIdList": "123,221,998"
          }
        },
        {
          "name": "GradualRolloutRandom",
          "parameters": {
            "percentage": "10"
          }
        }
      ],
      "strategy": "ActiveForUserWithId",
      "parameters": {
        "userIdList": "123,221,998"
      }
    }
  ]
}

Filter feature flags

Supports three params for now

• tag - filters for features tagged with tag
• project - filters for features belonging to project
• namePrefix - filters for features beginning with prefix

For tag and project performs OR filtering if multiple arguments

To filter for any feature tagged with a simple tag with value taga or a simple tag with value tagb use

GET https://unleash.host.com/api/client/features?tag[]=simple:taga&tag[]simple:tagb

To filter for any feature belonging to project myproject use

GET https://unleash.host.com/api/client/features?project=myproject

Response format is the same as api/client/features

Get specific feature flag

GET: http://unleash.host.com/api/client/features/:featureName

Used to fetch details about a specific feature flag. This is mainly provided to make it easy to debug the API and should not be used by the client implementations.

Notice: You will not get a version property when fetching a specific feature flag by name.

{
  "name": "Feature.A",
  "type": "release",
  "enabled": false,
  "stale": false,
  "strategies": [
    {
      "name": "default",
      "parameters": {}
    }
  ],
  "strategy": "default",
  "parameters": {}
}

Strategy Constraints

:::note Availability

Version: 4.16+

:::

Strategy definitions may also contain a constraints property. Strategy constraints is a feature in Unleash which work on context fields, which is defined as part of the Unleash Context. The purpose is to define a set of rules where all needs to be satisfied in order for the activation strategy to evaluate to true. A high level description of it is available online.

Example response:

The example shows strategy constraints in action. Constraints is a new field on the strategy-object. It is a list of constraints that need to be satisfied.

In the example environment needs to be production AND userId must be either 123 OR 44 in order for the Unleash Client to evaluate the strategy, which in this scenario is “default” and will always evaluate to true.

{
  "type": "release",
  "enabled": true,
  "stale": false,
  "name": "Demo",
  "strategies": [
    {
      "constraints": [
        {
          "contextName": "environment",
          "operator": "IN",
          "values": ["production"]
        },
        {
          "contextName": "userId",
          "operator": "IN",
          "values": ["123", "44"]
        }
      ],
      "name": "default",
      "parameters": {}
    }
  ]
}

• contextName - is the name of the field to look up on the unleash context.
• values - is a list of values (string).
• operator - is the logical action to take on the values Supported operator are:
  • IN - constraint is satisfied if one of the values in the list matches the value for this context field in the context.
  • NOT_IN - constraint is satisfied if NONE of the values is the list matches the value for this field in the context.

Variants

All feature flags can also take an array of variants. You can read more about feature flag variants.

{
  "version": 1,
  "features": [
    {
      "name": "Demo",
      "type": "operational",
      "enabled": true,
      "stale": false,
      "strategies": [
        {
          "name": "default"
        }
      ],
      "variants": [
        {
          "name": "red",
          "weight": 500,
          "weightType": "variable",
          "payload": {
            "type": "string",
            "value": "something"
          },
          "overrides": [
            {
              "contextName": "userId",
              "values": ["123"]
            }
          ]
        },
        {
          "name": "blue",
          "weight": 500,
          "overrides": [],
          "weightType": "variable"
        }
      ]
    }
  ]
}

• payload - an optional object representing a payload to the variant. Takes two properties if present type and value.
• overrides - an optional array of overrides. If any context field matches any of the the defined overrides it means that the variant should be selected.