hollaback

Hollaback

Resolves a Promise when host(s)/port(s) are ready

If your app needs to wait for database connections, microservices or other stuff being available first, holla' has your back.

You can use it like this (assuming async/await in Node.js):

# ... inside an async function
await hollaback(
  'web-host:80',
  'arangodb-host:8529'
);

// Do other stuff after web and ArangoDB are ready

I wrote this because I use Docker Compose a lot.

Just though Docker thinks a service is ready, doesn't mean it is. That means dependencies can break.

I wanted a simple wait to await a promise before moving on.

Hollaback is it.

Usage

Without hipster ES6/7 stuff:

const hollaback = require('hollaback');

hollaback('host1:port', 'host2:port').then(function () {
  // Our host names are available
});

For cool kids:

import hollaback from 'hollaback'

const hosts = [
  'host1:port',
  'host2:port'
];

(async function whenReady(){
  await hollaback(...hosts);
  // Our services are ready - go nuts...
  
}());

Pass either a list of host:port strings or an array of them, and hollaback will try all of them before resolving the promise.

Options

Under the hood, it uses Socket to probe a host/port.

By default, retries occur every 500ms until the port is available, and times out after 30 seconds.

You can override the defaults by passing an options object as the last param:

hollaback(hosts, {
    retry: 500, // per connection retry (in ms)
    timeout: 30 * 1000, // global timeout (rejects after this time, in ms)
    socketTimeout: 1000, // per connection timeout (in ms)
})

Compatibility

Designed for Node 5 and above.

Testing

Run npm run test

License

MIT