Overleash

Override your Unleash feature flags blazing fast 🚀

Overleash is a powerful developer tool that allows you to easily override feature flags on and off in your environment. It simplifies the process of making and testing changes that rely on feature flags, enabling faster iterations and smoother development without interrupting your teammates or the need for complex configurations.

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Features

• Dynamic Overrides: Override feature flags dynamically without modifying upstream configs.
• Dashboard: View and manage feature flags with ease.
• Multi-Token Support: Seamlessly test with multiple Unleash tokens.
• Blazing Fast: Fetch, cache, and reload feature flag configurations efficiently.
• Proxy Metrics: Enable metrics forwarding for your Unleash setup.

🚀 Quick Start

The simplest way to get started is by using the provided docker-compose configuration:

1. Copy the .env.example to .env and fill in your configuration options.
2. Run:

   docker compose up

Docker image

The Overleash Docker image is published to Docker Hub:

docker pull iandenh/overleash

Traefik

The docker-compose file provide as labels to register as a service Traefik 2+. For this to work correctly make sure to set the correct NETWORK_NAME. The default host name for optimizely is overleash.test.

Using in application

To use Overleash in your application, simply update your Unleash host:

From: https://unleash.mysite.com
To:   http://overleash.test

Yggdrasil - Frontend API

Overleash supports the Frontend API, powered by yggdrasil, the reusable Unleash SDK logic.

Note: This project uses a custom fork of Yggdrasil with additional FFI functions: resolve_all branch.

Local build

This project is created with golang version 1.23. For templating it also uses templ, so make sure that is installed. Generating templ templates can be done with templ generate

Because we are using yggdrasil you also need to make sure the libyggdrasilffi.so is correctly linked. This can be done with: export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:$(pwd)/unleashengine

Config

Setting the config for Overleash can be set in two ways, environment variable or cli flags.

Here are the config options:

Name	Value	Env	Flag
Unleash url	example: https://unleash.my-site.com, this url without /api, can be a Unleash instance or Unleash edge	OVERLEASH_URL	--url
Reload frequency	default: 0, example: 1, value is in minutes, 0 is no reload	OVERLEASH_RELOAD	--reload
Server port	default: 5433	OVERLEASH_PORT	--port
Unleash token (Client token)	example: *:development.a2a6261d38fe4f9c86aceddce09a00df6c348fd0feeab3c24a9547f2 Token or tokens that are used to fetch the feature flag config from upstream unleash.	OVERLEASH_TOKEN	--token
Verbose	default: false Logs a bit more information for diagnose issues	OVERLEASH_VERBOSE	--verbose
Proxy metrics to upstream	default: false Proxy the metric calls to the upstream. Make sure the correct token are in the authorization header.	OVERLEASH_PROXY_METRICS	--proxy-metrics

API Endpoints

Client API

Method	Endpoint	Description
GET	/api/client/features	Fetch all feature flags.
GET	/api/client/features/{key}	Fetch a specific feature flag.
POST	/api/client/metrics	Proxy metrics to Unleash server when proxy metrics is enabled, otherwise return always 200.
POST	/api/client/register	Register client. Always returns 200.

Frontend API

Method	Endpoint	Description
GET	/api/frontend	Fetch evaluated toggles.
POST	/api/frontend	Fetch toggles with custom context.
GET	/api/frontend/features/{featureName}	Fetch a specific feature evaluation.
POST	/api/frontend/client/metrics	Proxy metrics to Unleash server when proxy metrics is enabled, otherwise return always 200.
POST	/api/frontend/client/register	Register frontend client. Always returns 200.

Dashboard Overrides

These endpoints return html.

Method	Endpoint	Description
POST	/override/{key}/{enabled}	Override a feature flag true for enabled and false for disabled.
POST	/override/constrain/{key}/{enabled}	Add a constraint override.
DELETE	/override/{key}	Remove an override.
POST	/dashboard/refresh	Refresh feature flag data.
POST	/dashboard/pause	Pause Overleash updates.
POST	/dashboard/unpause	Resume Overleash updates.