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OpenFeature Provider

OpenFeature is an open standard that provides a vendor-agnostic, community-driven API for feature flagging that works with DevCycle.

DevCycle provides a Ruby implementation of the OpenFeature Provider interface, if you prefer to use the OpenFeature API.

GitHub

Usage​

Installation​

Install the OpenFeature Ruby SDK and DevCycle Provider:

gem install devcycle-ruby-server-sdk

or

bundler add devcycle-ruby-server-sdk

Getting Started​

Initialize the DevCycle SDK and set the DevCycleProvider as the provider for OpenFeature:

require 'open_feature/sdk'
require 'devcycle-ruby-server-sdk'

dvc_client = DevCycle::Client.new(ENV['DEVCYCLE_SERVER_SDK_KEY'], DevCycle::Options.new)
OpenFeature::SDK.configure do |config|
    config.set_provider(dvc_client.open_feature_provider)
end
@open_feature_client = OpenFeature::SDK.build_client

Evaluate a Variable​

Use a Variable value by setting the EvaluationContext, then passing the Variable key and default value to one of the OpenFeature flag evaluation methods.

context = OpenFeature::SDK::EvaluationContext.new(user_id:'user_id')
flag_value = @open_feature_client.fetch_integer_value(flag_key: 'flag_key', default_value: 1, evaluation_context: context)

Required Targeting Key​

For the DevCycle SDK to work we require either a targeting_key or user_id to be set on the OpenFeature context. This is used to identify the user as the user_id for a DevCycleUser in DevCycle.

Context properties to DevCycleUser​

The provider will automatically translate known DevCycleUser properties from the OpenFeature context to the DevCycleUser object. DevCycleUser Ruby Interface

For example all these properties will be set on the DevCycleUser:

# Pass context when querying values from the OpenFeature client
context = OpenFeature::SDK::EvaluationContext.new(
    user_id: 'user_id',
    email: 'email',
    name: 'name',
    appBuild: 1,
    appVersion: '1.0.0',
    randomField: 'value',
    privateCustomData: { 'secretkey' => 'secretvalue' },
    customData: { 'key' => 'value' })

Context properties that are not known DevCycleUser properties will be automatically added to the customData property of the DevCycleUser.

Context Limitations​

DevCycle only supports flat JSON Object properties used in the Context. Non-flat properties will be ignored.

For example obj will be ignored:

context = OpenFeature::SDK::EvaluationContext.new(
    user_id: 'user_id',
    obj: { 'secretkey' => 'secretvalue' })

JSON Flag Limitations​

The OpenFeature spec for JSON flags allows for any type of valid JSON value to be set as the flag value.

For example the following are all valid default value types to use with OpenFeature:

# Invalid JSON values for the DevCycle SDK, will return defaults
open_feature_client.fetch_object_value(flag_key: 'json-variable', default_value: 1.0, evaluation_context: context)
open_feature_client.fetch_object_value(flag_key: 'json-variable', default_value: false, evaluation_context: context)
open_feature_client.fetch_object_value(flag_key: 'json-variable', default_value: 'string', evaluation_context: context)
open_feature_client.fetch_object_value(flag_key: 'json-variable', default_value: nil, evaluation_context: context)

However, these are not valid types for the DevCycle SDK, the DevCycle SDK only supports JSON Objects:

# Valid JSON Object as the default value, will be evaluated by the DevCycle SDK
@client.fetch_object_value(flag_key: 'json-variable', default_value: { 'key' => 'value' }, evaluation_context: context)