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Getting Started ​

Verified against flagd v0.16.0 (commit 80b9e95). Commands assume Docker and a local shell.

Prerequisites ​

  • Docker (the published image is ghcr.io/open-feature/flagd).
  • A local port free for the evaluation service (8013) and OFREP (8016).
  • curl to test the OFREP REST endpoint.

Install ​

The simplest path is the container image; no build step is needed (6).

bash
docker pull ghcr.io/open-feature/flagd:latest

To build from source instead, the repository uses a Go workspace and a Makefile target (make build produces the flagd binary) (1).

A first working setup ​

  1. Write a flag definition file flags.json in the current directory. state enables the flag, variants lists the possible values, and defaultVariant is returned when no targeting matches.

    json
    {
  "flags": {
    "show-welcome-banner": {
      "state": "ENABLED",
      "variants": {
        "on": true,
        "off": false
      },
      "defaultVariant": "off"
    }
  }
}

  2. Start flagd, mounting the file and passing it as a file: sync source. The default flag ports are 8013 (evaluation), 8014 (management), 8015 (gRPC sync), and 8016 (OFREP) (flagd/cmd/start.go:53-56).

    bash
    docker run --rm -it \
  -p 8013:8013 -p 8016:8016 \
  -v "$(pwd)":/etc/flagd \
  ghcr.io/open-feature/flagd:latest \
  start --uri file:/etc/flagd/flags.json

  3. Evaluate the flag over OFREP (the REST evaluation API). An empty context evaluates with no targeting input.

    bash
    curl -X POST http://localhost:8016/ofrep/v1/evaluate/flags/show-welcome-banner \
  -H 'Content-Type: application/json' \
  -d '{"context": {}}'

The response carries the resolved value and a reason. With no targeting rule, the reason is STATIC and the value is the defaultVariant (core/pkg/evaluator/json.go:420).

Verify it works ​

  • The OFREP call above should return the off variant value (false) with reason STATIC.
  • Add a targeting JSONLogic rule to the flag and re-evaluate with a matching context; the reason changes to TARGETING_MATCH (core/pkg/evaluator/json.go:401-406).
  • A disabled flag ("state": "DISABLED") returns reason DISABLED (core/pkg/evaluator/json.go:349-352).

Where to go next ​

  • flagd documentation for sync sources beyond files (HTTP, Kubernetes CRD, gRPC, and blob storage) and the OpenFeature Operator for sidecar injection (1)(12).
  • The OpenFeature SDKs to call flagd from application code through a provider, rather than raw OFREP (5).
  • Official docs for production concerns such as TLS, OpenTelemetry export, and the flagd-proxy for fan-out (1)(12).