Gracefully start and stop express app

Allows one to start listening immediately and queue requests until app is ready to process.

// returns app
var app = require('express-graceful')(require('express')());

// start listening as usual
app.listen();

// ... do db initialization, add route, async operations
// when pending requests are ready to be processed
app.ready();

Because in complicated setups one could need the application to be listening before completely initialized. The daemon starting the application would then let requests be handled to it, leading to 503 service failures from the proxy in front of the express application.

wait for requests to finish before shutting down app