Node.js, express, and using development versus production in app.configure

Question

What is the easiest method to let express know what environment I am in? E.g. I want do do the below to make a connection to redis depending on what env I am in. Can this be done from the command line?

app.configure('development', function(){
  app.use(express.errorHandler({ dumpExceptions: true, showStack: true }));
  var r = require("redis").createClient(6379,'127.0.0.1');
});
app.configure('production', function(){
  app.use(express.errorHandler());
  r = redis.createClient(6379,'46.137.195.230', { detect_buffers: true });
});

Answer 1

Your approach is ok, but you can make something more generic, like storing the config data for Redis in a file or passing the host and port like arguments:

node app.js REDIS_HOST REDIS_PORT

Then in your app you can grab them using process.argv:

app.configure('development', function(){
  app.use(express.errorHandler({ dumpExceptions: true, showStack: true }));
  var r = require("redis").createClient(process.argv[2], process.argv[3]);
});
app.configure('production', function(){
  app.use(express.errorHandler());
  var r = require("redis").createClient(process.argv[2], process.argv[3], { detect_buffers: true });
});

Update:

Express will know in what environment you're in by looking at the NODE_ENV variable (process.env.NODE_ENV): https://github.com/visionmedia/express/blob/master/lib/application.js#L55

You can set that variable when starting the app like so: NODE_ENV=production node app.js (recommended), setting process.env.NODE_ENV manually in your node app before the Express code or putting that env var in ~/.profile like Ricardo said.