unleash.unleash/docs/getting-started.md

---
id: getting_started
title: Getting Started
---

## Requirements

You will need **Node.js** >= 12 and a **PostgreSQL** >= 10 database instance to be able to run Unleash.

When starting Unleash you must specify a database URI (can be set as environment variable DATABASE_URL) which includes a username and password, that have rights to migrate the database.

On startup _Unleash_ will perform necessary migrations if needed.

## Start Unleash

### 1. The simplest way to get started:

```bash
$ npm install unleash-server -g
$ unleash -d postgres://unleash_user:password@localhost:5432/unleash -p 4242

Unleash started on http://localhost:4242
```

### 2. Or programmatically:

You can also depend on unleash

```js
const unleash = require('unleash-server');

unleash
  .start({
    databaseUrl: 'postgres://unleash_user:password@localhost:5432/unleash',
    port: 4242,
  })
  .then(unleash => {
    console.log(
      `Unleash started on http://localhost:${unleash.app.get('port')}`,
    );
  });
```

Available unleash options include:
- **db** - The database configuration object taking the following properties:
  - *user* - the database username (`DATABASE_USERNAME`)
  - *password* - the database password (`DATABASE_PASSWORD`)
  - *host* - the database hostname (`DATABASE_HOST`)
  - *port* - the datbase port defaults to 5432 (`DATABASE_PORT`)
  - *database* - the database name to be used (`DATABASE_NAME`) 
  - *ssl* - an object describin ssl options, see https://node-postgres.com/features/ssl (`DATABASE_SSL`, as a stringified json object)
- **databaseUrl** - the postgres database url to connect to. Only used if _db_ object is not specified. Should include username/password. This value may also be set via the `DATABASE_URL` environment variable. Alternatively, if you would like to read the database url from a file, you may set the `DATABASE_URL_FILE` environment variable with the full file path. The contents of the file must be the database url exactly.
- **databaseSchema** - the postgres database schema to use. Defaults to 'public'.
- **port** - which port the unleash-server should bind to. If port is omitted or is 0, the operating system will assign an arbitrary unused port. Will be ignored if pipe is specified. This value may also be set via the `HTTP_PORT` environment variable
- **host** - which host the unleash-server should bind to. If host is omitted, the server will accept connections on the unspecified IPv6 address (::) when IPv6 is available, or the unspecified IPv4 address (0.0.0.0) otherwise. This value may also be set via the `HTTP_HOST` environment variable
- **pipe** - parameter to identify IPC endpoints. See https://nodejs.org/api/net.html#net_identifying_paths_for_ipc_connections for more details
- **enableLegacyRoutes** (boolean) - allows you to turn on/off support for legacy routes to support older clients. Disabled by default. Will be removed in 4.x.
- **serverMetrics** (boolean) - use this option to turn on/off prometheus metrics.
- **preHook** (function) - this is a hook if you need to provide any middlewares to express before `unleash` adds any. Express app instance is injected as first argument.
- **preRouterHook** (function) - use this to register custom express middlewares before the `unleash` specific routers are added. This is typically how you would register custom middlewares to handle authentication.
- **adminAuthentication** (string) - use this when implementing custom admin authentication [securing-unleash](./securing-unleash.md). Possible values are:
  - `none` - will disable authentication altogether
  - `unsecure` - (default) will use simple cookie based authentication. UI will require the user to specify an email in order to use unleash.
  - `custom` - use this when you implement your own custom authentication logic.
- **ui** (object) - Set of UI specific overrides. You may set the following keys: `headerBackground`, `environment`, `slogan`.
- **getLogger** (function) - Used to register a [custom log provider](#How do I configure the log output).
- **eventHook** (`function(event, data)`) - If provided, this function will be invoked whenever a feature is mutated. The possible values for `event` are `'feature-created'`, `'feature-updated'`, `'feature-archived'`, `'feature-revived'`. The `data` argument contains information about the mutation. Its fields are `type` (string) - the event type (same as `event`); `createdBy` (string) - the user who performed the mutation; `data` - the contents of the change. The contents in `data` differs based on the event type; For `'feature-archived'` and `'feature-revived'`, the only field will be `name` - the name of the feature. For `'feature-created'` and `'feature-updated'` the data follows a schema defined in the code [here](https://github.com/Unleash/unleash/blob/master/lib/routes/admin-api/feature-schema.js#L38-L59). See an example [here](./guides/feautre-updates-to-slack.md).
- **baseUriPath** (string) - use to register a base path for all routes on the application. For example `/my/unleash/base` (note the starting /). Defaults to `/`. Can also be configured through the environment variable `BASE_URI_PATH`.

#### Disabling Auto-Start

If you're using unleash as part of a larger express app, you can disable the automatic server start by calling `server.create`. It takes the same options as `sevrer.start`, but will not begin listening for connections.

```js
const unleash = require('unleash-server');
// ... const app = express();

unleash
  .create({
    databaseUrl: 'postgres://unleash_user:password@localhost:5432/unleash',
    port: 4242,
  })
  .then(result => {
    app.use(result.app);
    console.log(`Unleash app generated and attached to parent application`);
  });
```

### 3. Docker

You can also use the [hosted docker image](https://hub.docker.com/r/unleashorg/unleash-server/) to start the Unleash server

```sh
docker run -d -e DATABASE_URL=postgres://user:pass@10.200.221.11:5432/unleash unleashorg/unleash-server
```

## Securing Unleash

Unleash also have extension points where you can integrate Unleash with your authentication provider (OAuth 2.0). Read more about [securing unleash](./securing-unleash.md).

## How do I configure the log output?

By default, `unleash` uses [log4js](https://github.com/nomiddlename/log4js-node) to log important information. It is possible to swap out the logger provider (only when using Unleash programmatically). You do this by providing an implementation of the **getLogger** function as This enables filtering of log levels and easy redirection of output streams.

```javascript
function getLogger(name) {
  // do something with the name
  return {
    debug: console.log,
    info: console.log,
    warn: console.log,
    error: console.error,
  };
}
```

The logger interface with its `debug`, `info`, `warn` and `error` methods expects format string support as seen in `debug` or the JavaScript `console` object. Many commonly used logging implementations cover this API, e.g., bunyan, pino or winston.