Serving non-standard HTTP method with ExpressJS

问题:

I would like to write an HTTP server that answer to request using a non-standard HTTP method (verb). For instance, the client would make a request like FOO / HTTP/.1.1. And on the server side, this request would be handled by something like:

var express = require('express');

var app = express.createServer();

app.configure(function(){
  app.use(express.logger({ format: ':method :url' }));
  app.use(express.methodOverride());
});

app.foo('/', function(req, res){
    res.send('Hello World');
});

app.listen(3000);

I appended my non-standard method to the array exported in ExpressJS's lib/router/methods.js. This allow me to write my server code as expected. When using express.methodOverride() and a POST request with _method=foo, it works. But an actual FOO request doesn't work. As soon as the client send the first line of the request the connection is closed by the server:

$telnet localhost 3000
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
FOO / HTTP/1.1
Connection closed by foreign host.

I would like to be able to implement this with ExpressJS and without avoid hacking into its core file.

Any idea if this is possible and how?

回答1:

Short answer: No, it's not possible. Not without implementing your own HTTP module.

To test, start a barebones HTTP server ...

$ node
> require('http').createServer(function(req, res) {
...   console.log(req.method);
...   res.end();
... }).listen(8080);

Then (as you've already done) telnet to it and issue a GET and FOO request ...

$ telnet localhost 8080
Trying ::1...
telnet: connect to address ::1: Connection refused
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
GET / HTTP/1.1

HTTP/1.1 200 OK
Connection: keep-alive
Transfer-Encoding: chunked

0

FOO / HTTP/1.1
Connection closed by foreign host.

$ 

In node console you'll see

GET

... but no FOO. So, node's native HTTP module, which Express uses, does not make these requests available.

回答2:

Node has a hard-coded whitelist of acceptable HTTP verbs in C.

In order to accept custom verbs, you must modify the HTTP parser and recompile node.

---

You mentioned that you're trying to implement PURGE, which was added to the whitelist in v0.7.5.

回答3:

As others have said, Node.js' HTTP server library is configured to accept only specific verbs. Ben Noordius' suggestion of using Parsley doesn't work either, since that library accepts an even smaller whitelist of verbs. (It also hasn't been maintained in quite some time.)

At this stage, if we want to support oddball requests, we have to take more drastic measures. Here's a nice ugly hack for you that involves duck punching some internal behavior. This works on v0.10.x of Node.js, but test carefully on newer versions as they become available.

In my case, I needed to support not only a non-standard verb, but a non-standard protocol version identifier as well, and a missing Content-Length header for Icecast source streams:

SOURCE /live ICE/1.0

The following should get you started:

server.on('connection', function (socket) {
    var originalOnDataFunction = socket.ondata;
    var newLineOffset;
    var receiveBuffer = new Buffer(0);
    socket.ondata = function (d, start, end) {
        receiveBuffer = Buffer.concat([receiveBuffer, d.slice(start, end)]);
        if ((newLineOffset = receiveBuffer.toString('ascii').indexOf('\n')) > -1) {
            var firstLineParts = receiveBuffer.slice(0, newLineOffset).toString().split(' ');
            firstLineParts[0] = firstLineParts[0].replace(/^SOURCE$/ig, 'PUT');
            firstLineParts[2] = firstLineParts[2].replace(/^ICE\//ig, 'HTTP/');
            receiveBuffer = Buffer.concat([
                new Buffer(
                    firstLineParts.join(' ') + '\r\n' + 
                    'Content-Length: 9007199254740992\r\n'
                ), 
                receiveBuffer.slice(newLineOffset +1)
            ]);

            socket.ondata = originalOnDataFunction;
            socket.ondata.apply(this, [receiveBuffer, 0, receiveBuffer.length]);
        }
    };
}

It's ugly, but works. I'm not particularly happy about it, but when choosing between a rough built-from-the-ground-up HTTP parser or tweaking an existing one, I choose to tweak in this instance.

回答4:

Is there a truly significant purpose to this? Only your own HTTP server and client would be able to talk to each other, and it seems like a large amount of effort for a very tiny gain. In what way do the standard HTTP verbs fail you?

To answer your question on whether or not this would require hacking into Express: it will require digging into it. Express requires the http module, and you'd need to override that with your own, at least. Node.js's built-in core modules are always checked first, so you can't just give your module the same name to do that.