A feature flag daemon with a Unix philosophy.

What's flagd?

flagd is a feature flag daemon with a Unix philosophy. Think of it as a ready-made, open source, OpenFeature-compliant feature flag backend system.

Features

• 🌐 OpenFeature compliant and speaks your language.
• 🆕 Easy to extend to new languages.
• 🔄 Supports multiple data sources simultaneously.
• 🕒 Feature Flag updates occur in near real-time.
• 💪 Contains a powerful and flexible rule targeting engine and deterministic percentage-based rollouts.
• 🔦 Flag evaluation traces and metrics are exposed and compatible with OpenTelemetry.

▶️ Quick Start

Experiment with flagd in your browser using the Killercoda tutorial or follow the instructions below to run on your own infrastructure.

1. flagd can be run as a standalone binary or container. Download and install flagd or run it as a container

1. Start flagd:

flagd start \
      --port 8013 \
      --uri https://raw.githubusercontent.com/open-feature/flagd/main/samples/example_flags.flagd.json

Or use docker: _Note - In Windows, use WSL system for both the file location and Docker runtime. Mixed file systems don't work and this is a limitation of Docker_

docker run \
      --rm -it \
      --name flagd \
      -p 8013:8013 \
      ghcr.io/open-feature/flagd:latest start \
      --uri https://raw.githubusercontent.com/open-feature/flagd/main/samples/example_flags.flagd.json

If you wish, download the file locally to make changes:

wget https://raw.githubusercontent.com/open-feature/flagd/main/samples/example_flags.flagd.json

In local mode, run flagd like this:

flagd start \
      --port 8013 \
      --uri file:./example_flags.flagd.json

Or use docker ( _Note - In Windows, this requires WSL system for both the file location and Docker runtime_):

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

--uri can be a local file or any remote endpoint. Use file: prefix for local files. eg. --uri file:/path/to/example_flags.flagd.json. gRPC and http have their own requirements. More information can be found here.

Multiple --uri parameters can be specified. In other words, flagd can retrieve flags from multiple sources simultaneously.

1. Flagd is now ready to perform flag evaluations over either HTTP(s) or gRPC. This example utilizes HTTP via cURL.

curl -X POST "http://localhost:8013/flagd.evaluation.v1.Service/ResolveString" \
      -d '{"flagKey":"myStringFlag","context":{}}' -H "Content-Type: application/json"

For Windows we recommend using a WSL terminal. Otherwise, use the following with cmd:

set json={"flagKey":"myStringFlag","context":{}}
    curl -i -X POST -H "Content-Type: application/json" -d %json:"=\"% "localhost:8013/flagd.evaluation.v1.Service/ResolveString"

Result:

{
      "value": "val1",
      "reason": "DEFAULT",
      "variant":"key1"
    }

Updates to the underlying flag store (e.g. JSON file) are reflected by flagd in realtime. No restart is required.

flagd also supports boolean, integer, float and object flag types.

1. Now that flagd is running, it is time to integrate it into your application. Do this by using an OpenFeature provider in a language of your choice.

📐 High-level Architecture

!logical architecture of flagd

📝 Further Documentation

Further documentation including flagd configuration options, fractional evaluation, targeting rules and flag configuration merging strategies can be found at flagd.dev or in this repository.

🫶 Contributing

Interested in contributing? Great, we'd love your help! To get started, take a look at the CONTRIBUTING guide.

We also hold regular community meetings that are open to everyone. Check the OpenFeature community page for all the ways to get involved.

Thanks so much to our contributors.

Made with contrib.rocks.

License

Apache License 2.0