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.

Answer 2

To expand on the idea of using a config.json file:

// config.json {   "development": {     "redisPort": 6379,     "redisHost": "127.0.0.1",     "errorHandlerOptions": {"dumpExceptions": true, "showStack": true}   },   "production": {     "redisPort": 6379,     "redisHost": "46.137.195.230",     "errorHandlerOptions": {"dumpExceptions": false, "showStack": false}   } } 

Load the config file and switch based on env.

// app.js var config = require('./config.json')[app.get('env')]; app.use(express.errorHandler(config.errorHandlerOptions)); var r = require("redis").createClient(config.redisPort,config.redisHost); 

Make sure the NODE_ENV is set on each server (see other answers, one way: NODE_ENV=production node app.js), and this way the config variable has the settings appropriate to the server it runs on.