in_process_configuration.md

Feature Flag In-process Configuration

The InProcessConfiguration is a custom resource used to set up the configuration options for applications using OpenFeature operator with in-process evaluation mode enabled.

Below you can see a minimal example of InProcessConfiguration resource

apiVersion: core.openfeature.dev/v1beta1
kind: InProcessConfiguration
metadata:
  labels:
  name: inprocessconfiguration-sample
spec:
  port: 2424
  tls: true
  offlineFlagSourcePath: "my-path"
  cacheMaxSize: 11
  envVarPrefix: "my-prefix"
  envVars:
    - name: "name1"
      value: "val1"
    - name: "name2"
      value: "val2"

How does it work?

Similar to usage of FeatureFlagSource configuration, annotations are used to allow the injection of configuration data into the annotated Pod. The mutating webhook parses the annotations, retrieves the referenced InProcessConfiguration resources from the cluster and injects the data from the resource into all containers of the Pod via environment variables, which configure the provider in the workload to consume feature flag configuration from the available sync implementation specified by the configuration.

Merging of configurations

The value of openfeature.dev/inprocessconfiguration annotation is a comma separated list of values following one of two patterns: {NAME} or {NAMESPACE}/{NAME}. If no namespace is provided, it is assumed that the CR is within the same namespace as the deployed pod, for example:

metadata:
  annotations:
    openfeature.dev/enabled: "true"
    openfeature.dev/inprocessconfiguration: "inProcessConfig-A, inProcessConfig-B"

When multiple InProcessConfigurations are provided, the custom resources are merged in runtime and the last CR takes precedence over the first, similarly how it's done for FeatureFlagSource. In this example, 2 CRs are being used to set the injected configuration.

apiVersion: core.openfeature.dev/v1beta1
kind: InProcessConfiguration
metadata:
    name: inProcessConfig-A
spec:
    port: 2424
    tls: true
    offlineFlagSourcePath: "my-path"
    cacheMaxSize: 11
    envVarPrefix: "my-prefix"
    envVars:
      - name: "name1"
        value: "val1"
      - name: "name2"
        value: "val2"
---
apiVersion: core.openfeature.dev/v1beta1
kind: InProcessConfiguration
metadata:
    name: inProcessConfig-B
spec:
    envVarPrefix: "my-second-prefix"
    host: "my-host"

The resources are merged in runtime, which means that no changes are made to the InProcessConfiguration resources in the cluster, but the operator handles the merge and injection internally.

The resulting configuration will look like the following

apiVersion: core.openfeature.dev/v1beta1
kind: InProcessConfiguration
metadata:
    name: internal
spec:
    port: 2424
    tls: true
    offlineFlagSourcePath: "my-path"
    cacheMaxSize: 11
    envVarPrefix: "my-seconf-prefix"
    host: "my-host"
    envVars:
      - name: "name1"
        value: "val1"
      - name: "name2"
        value: "val2"

This resulting resource is transformed into environment variables and injected into all containers of the annotated Pod

apiVersion: v1
kind: Pod
metadata:
  annotations:
    openfeature.dev/enabled: "true"
    openfeature.dev/inprocessconfiguration: "inProcessConfig-A, inProcessConfig-B"
  name: ofo-pod
spec:
  containers:
    - name: container1
      image: image1
      env:
        - name: my-second-prefix_name2
          value: val2
        - name: my-second-prefix_name1
          value: val1
        - name: my-second-prefix_HOST
          value: my-host
        - name: my-second-prefix_PORT
          value: "2424"
        - name: my-second-prefix_TLS
          value: "true"
        - name: my-second-prefix_OFFLINE_FLAG_SOURCE_PATH
          value: my-path
        - name: my-second-prefix_MAX_CACHE_SIZE
          value: "11"
        - name: my-second-prefix_RESOLVER
          value: in-process
    - name: container2
      image: image2
      env:
        - name: my-second-prefix_name2
          value: val2
        - name: my-second-prefix_name1
          value: val1
        - name: my-second-prefix_HOST
          value: my-host
        - name: my-second-prefix_PORT
          value: "2424"
        - name: my-second-prefix_TLS
          value: "true"
        - name: my-second-prefix_OFFLINE_FLAG_SOURCE_PATH
          value: my-path
        - name: my-second-prefix_MAX_CACHE_SIZE
          value: "11"
        - name: my-second-prefix_RESOLVER
          value: in-process