The Unleash Proxy

The Unleash Proxy simplifies integration with frontend & native applications running in the context of a specific user. The Unleash proxy sits between the proxy SDK and the Unleash API and ensures that you internal feature toggle configuration is not exposed to the world.

The proxy offers:

• High performance - a single proxy instance can handle thousands req/s, and can be horizontally scaled.
• Privacy for end-users - Your end users are not exposed to the unleash API and can be hosted by you This ensures no user data (userId, IPs, etc) is shared.
• Secure - It is controlled by you, and can hosted on your domain. In addition no feature toggle configuration is shared with the user, only evaluated toggles.

You can read more about the proxy in our documentation

Run The Unleash Proxy

The Unleash proxy is a small stateless HTTP application you run. The only requirement is that it needs to be able to talk with the Unleash API (either Unleash OSS or Unleash Hosted).

Run with Docker

The easies way to run Unleash is via Docker. We have published a docker image on docker hub.

Step 1: Pull

docker pull unleashorg/unleash-proxy

Step 2: Start

docker run \
   -e UNLEASH_PROXY_SECRETS=some-secret \
   -e UNLEASH_URL=https://app.unleash-hosted.com/demo/api/ \
   -e UNLEASH_API_TOKEN=56907a2fa53c1d16101d509a10b78e36190b0f918d9f122d \
   -p 3000:3000 \
   unleashorg/unleash-proxy

You should see the following output:

Unleash-proxy is listening on port 3000!

Step 3: verify

In order to verify the proxy you can use curl and see that you get a few evaluated feature toggles back:

curl http://localhost:3000/proxy -H "Authorization: some-secret"  

Expected output would be something like:

{
	"toggles": [{
		"name": "demo",
		"enabled": true,
		"variant": {
			"name": "disabled",
			"enabled": false
		}
	}, {
		"name": "demoApp.step1",
		"enabled": true,
		"variant": {
			"name": "disabled",
			"enabled": false
		}
	}]
}

Health endpoint

The proxy will try to synchronize with the Unleash API at startup, until it has successfully done that the proxy will return HTTP 503 - Not Read? for all request. You can use the health endpoint to validate that the proxy is ready to recieve requests:

curl http://localhost:3000/proxy/health -I

HTTP/1.1 200 OK
Access-Control-Allow-Origin: *
Access-Control-Expose-Headers: ETag
Content-Type: text/html; charset=utf-8
Content-Length: 2
ETag: W/"2-eoX0dku9ba8cNUXvu/DyeabcC+s"
Date: Fri, 04 Jun 2021 10:38:27 GMT
Connection: keep-alive
Keep-Alive: timeout=5

Available options

Option	Environment Variable	Default value	Required	Description
unleashUrl	UNLEASH_URL	n/a	yes	API Url to the Unleash instance to connect to
unleashApiToken	UNLEASH_API_TOKEN	n/a	yes	API token (client) needed to connect to Unleash API.
proxySecrets	UNLEASH_PROXY_SECRETS	n/a	yes	List of proxy secrets the proxy accept. Proxy SDKs needs to set the Proxy secret as the Authorization heder when querying the proxy
proxyPort	PORT	3000	no	The port where the proxy should listen.
proxyBasePath	PROXY_BASE_PATH	"/proxy"	no	The base path to run the proxy from. Defaults to "/proxy"
unleashAppName	UNLEASH_APP_NAME	"unleash-proxy"	no	App name to used when registering with Unleash
unleashInstanceId	UNLEASH_INSTANCE_ID	generated	no	Unleash instance id to used when registering with Unleash
refreshInterval	UNLEASH_FETCH_INTERVAL	5000	no	How often the proxy should query Unleash for updates, defined in ms.
metricsInterval	UNLEASH_METRICS_INTERVAL	30000	no	How often the proxy should send usage metrics back to Unleash, defined in ms.
environment	UNLEASH_ENVIRONMENT	undefined	no	If set this will be the environment used by the proxy in the Unleash Context. It will not be possible for proxy SDKs to override the environment if set.
projectName	UNLEASH_PROJECT_NAME	undefined	no	The projectName (id) to fetch feature toggles for. The proxy will only return know about feature toggles that belongs to the project, if specified.
logger	n/a	SimpleLogger	no	Register a custom logger.
logLevel	LOG_LEVEL	"warn"	no	Used to set logLevel. Supported options: "debug", "info", "warn", "error" and "fatal"
customStrategies	UNLEASH_CUSTOM_STRATEGIES_FILE	[]	no	Use this option to inject implementation of custom activation strategies. If you are using UNLEASH_CUSTOM_STRATEGIES_FILE you need to provide a valid path to a javascript files which exports an array of custom activation strategies and the SDK will automatically load these
trustProxy	TRUST_PROXY	false	no	By enabling the trustProxy option, Unleash Proxy will have knowledge that it's sitting behind a proxy and that the X-Forwarded-* header fields may be trusted, which otherwise may be easily spoofed. The proxy will automatically enrich the ip address in the Unleash Context. Can either be true/false (Trust all proxies), trust only given IP/CIDR (e.g. '127.0.0.1') as a string. May be a list of comma separated values (e.g. '127.0.0.1,192.168.1.1/24'
namePrefix	UNLEASH_NAME_PREFIX	undefined	no	Used to filter features by using prefix when requesting backend values.
tags	UNLEASH_TAGS	undefined	no	Used to filter features by using tags set for features. Format should be tagName:tagValue,tagName2:tagValue2

Run with Node.js:

STEP 1: Install dependency

 npm install @unleash/proxy

STEP 2: use in your code

const port = 3000;

const { createApp } = require('@unleash/proxy');


const app = createApp({
    unleashUrl: 'https://app.unleash-hosted.com/demo/api/',
    unleashApiToken: '56907a2fa53c1d16101d509a10b78e36190b0f918d9f122d',
    proxySecrets: ['proxy-secret', 'another-proxy-secret', 's1'],
    refreshInterval: 1000,
    // logLevel: 'info',
    // projectName: 'order-team',
    // environment: 'development',
});

app.listen(port, () =>
    // eslint-disable-next-line no-console
    console.log(`Unleash Proxy listening on http://localhost:${port}/proxy`),
);

Proxy clients

To make the integration simple we have developed proxy client SDKs. You can find them all in our documentation:

• JavaScript Proxy SDK (browser)
• Android Proxy SDK
• iOS Proxy SDK