Auto-reload of files in Node.js

Question

Any ideas on how I could implement an auto-reload of files in node.js. I'm tired of restarting the server every time I change a file. Apparently Node.js' require() function does not reload files if they already have been required, so I need to do something like this:

var sys     = require('sys'), 
    http    = require('http'),
    posix   = require('posix'),
    json    = require('./json');

var script_name      = '/some/path/to/app.js';
this.app     = require('./app').app;

process.watchFile(script_name, function(curr, prev){
    posix.cat(script_name).addCallback(function(content){
        process.compile( content, script_name );
    });
});

http.createServer(this.app).listen( 8080 );

And in the app.js file I have:

var file = require('./file');
this.app = function(req, res) { 
    file.serveFile( req, res, 'file.js');  
}

But this also isn't working - I get an error in the process.compile() statement saying that 'require' is not defined. process.compile is evaling the app.js, but has no clue about the node.js globals.

Answer 1

I also wondered about reloading modules. I modified node.js and have published the source at Github at nalply/node. The only difference is the function require. It has an optional second argument reload.

require(url, reload)

To reload app.js in current directory use

app = require("./app", true);

Write something like this, and you have auto-reload:

process.watchFile(script_name, function(curr, prev) {
    module = reload(script_name, true);
});

The only problem I see is the variable module, but I am working at it now.

Answer 2

Take a look at require.hot() patch by Felix Geisendörfer. I use it with modified Nerve framework.

Answer 3

There was a recent thread about this subject on the node.js mailing list. The short answer is no, it's currently not possible auto-reload required files, but several people have developed patches that add this feature.

Answer 4

There is Node-Supervisor that you can install by

npm install supervisor

see http://github.com/isaacs/node-supervisor

Answer 5

Here is a blog post about Hot Reloading for Node. It provides a github Node branch that you can use to replace your installation of Node to enable Hot Reloading.

From the blog:

var requestHandler = require('./myRequestHandler');

process.watchFile('./myRequestHandler', function () {
  module.unCacheModule('./myRequestHandler');
  requestHandler = require('./myRequestHandler');
}

var reqHandlerClosure = function (req, res) {
  requestHandler.handle(req, res);
}

http.createServer(reqHandlerClosure).listen(8000);

Now, any time you modify myRequestHandler.js, the above code will no­tice and re­place the local re­questHandler with the new code. Any ex­ist­ing re­quests will con­tin­ue to use the old code, while any new in­com­ing re­quests will use the new code. All with­out shut­ting down the serv­er, bounc­ing any re­quests, pre­ma­ture­ly killing any re­quests, or even re­ly­ing on an in­tel­li­gent load bal­ancer.

Answer 6

solution at: http://github.com/shimondoodkin/node-hot-reload

notice that you have to take care by yourself of the references used.

that means if you did : var x=require('foo'); y=x;z=x.bar; and hot reloaded it.

it means you have to replace the references stored in x, y and z. in the hot reaload callback function.

some people confuse hot reload with auto restart my nodejs-autorestart module also has upstart integration to enable auto start on boot. if you have a small app auto restart is fine, but when you have a large app hot reload is more suitable. simply because hot reload is faster.

Also I like my node-inflow module.