@unleash/proxy

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 your 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_CLIENT_KEYS=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.
clientKeys	UNLEASH_PROXY_CLIENT_KEYS	n/a	yes	List of client keys that the proxy should accept. When querying the proxy, Proxy SDKs must set the request's client keys header to one of these values. The default client keys header is Authorization.
proxySecrets	UNLEASH_PROXY_SECRETS	n/a	no	Deprecated alias for clientKeys. Please use clientKeys instead.
n/a	PORT or PROXY_PORT	3000	no	The port where the proxy should listen.
proxyBasePath	PROXY_BASE_PATH	""	no	The base path to run the proxy from. "/proxy" will be added at the end. For instance, if proxyBasePath is "base/path", the proxy will run at /base/path/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.
useJsonLogger	JSON_LOGGER	false	no	Sets the default logger to log as one-line JSON. This has no effect if a custom logger is provided.
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
clientKeysHeaderName	CLIENT_KEY_HEADER_NAME	"authorization"	no	The name of the HTTP header to use for client keys. Incoming requests must set the value of this header to one of the Proxy's clientKeys to be authorized successfully.
enableOAS	ENABLE_OAS	false	no	Set to true to expose the proxy's OpenAPI spec at /docs/openapi.json and an interactive OpenAPI UI at /docs/openapi. Read more in the OpenAPI section.
enableAllEndpoint	ENABLE_ALL_ENDPOINT	false	no	Set to true to expose the /proxy/all endpoint. Refer to the section on returning all toggles for more info.
cors	n/a	n/a	no	Pass custom options for CORS module
cors.allowedHeaders	CORS_ALLOWED_HEADERS	n/a	no	Headers to allow for CORS
cors.credentials	CORS_CREDENTIALS	false	no	Allow credentials in CORS requests
cors.exposedHeaders	CORS_EXPOSED_HEADERS	"ETag"	no	Headers to expose for CORS
cors.maxAge	CORS_MAX_AGE	172800	no	Maximum number of seconds to cache CORS results
cors.methods	CORS_METHODS	"GET, POST"	no	Methods to allow for CORS
cors.optionsSuccessStatus	CORS_OPTIONS_SUCCESS_STATUS	204	no	If the Options call passes CORS, which http status to return
cors.origin	CORS_ORIGIN	*	no	Origin URL or list of comma separated list of URLs to whitelist for CORS
cors.preflightContinue	CORS_PREFLIGHT_CONTINUE	false	no

Experimental options

Some functionality is under validation and introduced as experimental, to allow us to test new functionality early. You should expect these to change in any future feature release.

Option	Environment Variable	Default value	Required	Description
expBootstrap	n/a	n/a	no	Where the Proxy can bootstrap configuration from. See Node.js SDK for details.
expBootstrap.url	EXP_BOOTSTRAP_URL	n/a	no	Url where the Proxy can bootstrap configuration from. See Node.js SDK for details.
expBootstrap.urlHeaders.Authorization	EXP_BOOTSTRAP_AUTHORIZATION	n/a	no	Authorization header value to be used when bootstrapping
expServerSideSdkConfig.tokens	EXP_SERVER_SIDE_SDK_CONFIG_TOKENS	n/a	no	API tokens that can be used by Server SDKs (and proxies) to read feature toggle configuration from this Proxy instance.

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',
    clientKeys: ['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

OpenAPI

The proxy can optionally expose a runtime-generated OpenAPI JSON spec and a corresponding OpenAPI UI for its API. The OpenAPI UI page is an interactive page where you can discover and test the API endpoints the proxy exposes. The JSON spec can be used to generate an OpenAPI client with OpenAPI tooling such as the OpenAPI generator.

To enable the JSON spec and UI, set ENABLE_OAS (environment variable) or enableOAS (in-code configuration variable) to true.

The spec and UI can then be found at <base url>/docs/openapi.json and <base url>/docs/openapi respectively.

Return enabled and disabled toggles

By default, the proxy only returns enabled toggles. However, in certain use cases, you might want it to return all toggles, regardless of whether they're enabled or disabled. The /proxy/all endpoint does this.

Because returning all toggles regardless of their state is a potential security vulnerability, the endpoint has to be explicitly enabled. To enable it, set the enableAllEndpoint configuration option or the ENABLE_ALL_ENDPOINT environment variable to true.