GO Feature Flag Provider
The GO Feature Flag provider connects to a GO Feature Flag relay proxy and evaluates feature flags in-process. Flag definitions are fetched over HTTP and kept up-to-date via Server-Sent Events (SSE), then evaluated locally using a compiled WebAssembly engine, so no network call is made during flag evaluation.
This extension depends on:
| Component | Version | Source |
|---|---|---|
GO Feature Flag engine (WASM) |
0.2.2 |
Installation
<dependency>
<groupId>io.quarkiverse.openfeature</groupId>
<artifactId>quarkus-openfeature-gofeatureflag</artifactId>
<version>1.0.0.Alpha1</version>
</dependency>Configuration
By default, the provider connects to http://localhost:1031.
To connect to a different relay proxy:
quarkus.openfeature.gofeatureflag.url=https://goff.example.comFor named domains:
quarkus.openfeature."experimentation".gofeatureflag.url=https://goff-experiments.example.comTLS
The provider uses the Quarkus TLS registry for TLS configuration.
First, configure a named TLS configuration in application.properties, then reference it:
quarkus.tls.goff.trust-store.pem.certs=ca.pem
quarkus.openfeature.gofeatureflag.tls-configuration-name=goffSee the Quarkus TLS registry documentation for all available options.
Authentication
The provider supports API key authentication:
quarkus.openfeature.gofeatureflag.api-key=my-secret-keySetting api-key directly in configuration is suitable for development and testing.
For production, use a credentials provider such as Vault:
quarkus.openfeature.gofeatureflag.credentials-provider=goff-token
quarkus.openfeature.gofeatureflag.credentials-provider-name=vault-credentials-providerEvaluation context
A targeting key is mandatory in GO Feature Flag and if it is missing, the evaluation may return an error with code TARGETING_KEY_MISSING.
All other context attributes are passed through to the evaluation engine as generic context properties.
Dev Services
In dev and test mode, a GO Feature Flag relay proxy container is started automatically if no quarkus.openfeature.gofeatureflag.url is configured and Docker is available.
If no flag definition file is found, the relay proxy starts with an empty configuration.
To provide flag definitions to the dev service, place a flags.goff.yaml file in src/main/resources:
my-feature:
variations:
enabled: true
disabled: false
defaultRule:
variation: enabled
greeting:
variations:
hello: hello
howdy: howdy
defaultRule:
variation: hello| See the create flags reference for the complete format. |
The dev service picks up this file automatically. You can also configure a different path:
quarkus.openfeature.gofeatureflag.devservices.path=my-flags.yamlChanges to the flag definition file are detected during live reload and the application is restarted automatically. The relay proxy picks up the updated file through its own file watcher.
Evaluation concurrency
Flag evaluation runs locally in a WebAssembly engine. Each engine instance can only evaluate one flag at a time, so a pool of engine instances is maintained. The pool size controls the maximum number of concurrent flag evaluations; the default is 16. If all instances are in use, an evaluation request waits up to 100 milliseconds for an instance to become available. If no instance is available within that time, the default value is returned. To increase the pool size:
quarkus.openfeature.gofeatureflag.wasm-instances=32Connection lifecycle
The provider fetches the full flag configuration on startup and then subscribes to the relay proxy’s SSE stream for real-time updates. On connection loss, it automatically re-fetches the full configuration and reconnects to the stream. The provider lifecycle follows the OpenFeature specification:
- READY
-
The provider has received flag data and is serving evaluations.
- STALE
-
The connection was lost. The provider continues serving cached flag values while reconnecting.
- ERROR
-
The provider did not reconnect within the grace period (default 1 minute).
- FATAL
-
The server returned an authentication error (HTTP 401 or 403). The provider will not attempt to reconnect.
The grace period is configurable:
quarkus.openfeature.gofeatureflag.grace-period=10mConfiguration Reference
Configuration property fixed at build time - All other configuration properties are overridable at runtime
Configuration property |
Type |
Default |
|---|---|---|
If DevServices has been explicitly enabled or disabled. DevServices is generally enabled by default, unless there is an existing configuration present. When DevServices is enabled Quarkus will attempt to automatically configure and start a GO Feature Flag relay proxy instance when running in Dev or Test mode and when Docker is running. Environment variable: |
boolean |
|
The container image name to use, for container based DevServices providers. Environment variable: |
string |
|
Optional fixed port the dev service will listen to. If not defined, the port will be chosen randomly. Environment variable: |
int |
|
Path to a flag definition file on the classpath. If not configured explicitly and the default Environment variable: |
string |
|
Indicates if the GO Feature Flag instance managed by Quarkus Dev Services is shared. When shared, Quarkus looks for running containers using label-based service discovery. If a matching container is found, it is used, and so a second one is not started. Otherwise, Dev Services for GO Feature Flag starts a new container. The discovery uses the Container sharing is only used in dev mode. Environment variable: |
boolean |
|
The value of the This property is used when you need multiple shared GO Feature Flag servers. Environment variable: |
string |
|
GO Feature Flag relay proxy URL. Environment variable: |
string |
|
API key for authentication with the relay proxy. Environment variable: |
string |
|
The credentials provider name. This is the key used to look up credentials in the credentials provider. Environment variable: |
string |
|
The credentials provider bean name. This is a bean name (as in For Vault, the credentials provider bean name is Environment variable: |
string |
|
TLS configuration name from the Quarkus TLS registry. Environment variable: |
string |
|
Grace period before transitioning from STALE to ERROR after a connection loss. During this period, the provider continues serving cached flag values while attempting to reconnect. If the connection is restored within the grace period, the provider transitions back to READY without emitting an ERROR event. Environment variable: |
|
|
Number of WASM engine instances in the evaluation pool. Each engine can evaluate one flag at a time, so this controls the maximum concurrency of flag evaluations. Environment variable: |
int |
|
Whether to use the Quarkus-managed Environment variable: |
boolean |
|
|
About the Duration format
To write duration values, use the standard You can also use a simplified format, starting with a number:
In other cases, the simplified format is translated to the
|