gpusher

gpusher 📝

Git over HTTP with Push and Fetch Events

Fork of substack/pushover and strongloop-forks/strong-fork-pushover

gpusher allows one to have control as a middleware between git and the http transport. It does so by providing *.git/* routes over (req,res), executing rpc calls to git and then streaming back the response of such calls.

Quickstart

Fetch the package:

npm i gpusher

set up the handler:

const express = require('express');
const gpusher = require('gpusher');

const port = 8000;
const app = express();
const repos = gpusher('/tmp/gpusher');

repos.on('push', p => {
  console.log(
    'branch=%s\nrepo=%s\ncommit=%s',
    p.branch, p.commit, p.repo,
  );
  p.accept();
});

app.all('/*', repos.handle.bind(repos)); 

app.listen(port, () => {
  console.log('listening on %d', port);
});

Clone a repository:

git clone http://localhost:8000/myrepo

Push something to there:

cd myrepo
echo "hue" > file.txt
git add --all .
git commit -m 'something'
git push origin master

See the output in the server stdout:

listening on 8000
branch=master
repo=8788e1576ba150daeff969e74107a9ffbfa20b1c
commit=myrepo

Use cases

Rate-limiting big pushes

The handle function takes three arguments, being the last one an optional opts mapping:

function handle (req, res, opts);

where opts can take the following values:

// a function that takes a repository (string) and returns
// a `through` function that takes a chunk and then decides what 
// to do with it. In order to forward the chunk into the next pipe
// just `this.queue(chunk)`;
opts.transform = function (repo) { 
  // return a `through` function
  return function (chunk) { 
    this.queue(chunk);
  }
}

This transform method creator allows one to inject code into the pipe stream from request to git rpc sitting right after the decoding phase (when gzip decoder is sending bytes ahead).

This way one can create a rate-limiter:

  let server = http.createServer((req, res) => {
    function rateLimitter(repo) {
      let limit = 1024;
      return function bytesCounter(chunk) {
        limit -= chunk.length;
        if (limit > 0) {
          return this.queue(chunk);
        }

        this.emit('error', new Error('quota limit reached'));
      };
    }

    repos.handle(req, res, {
      transform: rateLimitter,
    });
  });

Performing a request and streaming the response to the client

const fs = require('fs');
const http = require('http');

const request = require('request');
const gpusher = require('gpusher');
const through2 = require('through2');
const sideband = require('git-side-band-message');

const repos = gpusher('/tmp/repositories');

repos.on('push', push => {
  console.log('push');

  push.on('response', (res, done) => {
    // this is a 3MB+ stream from 1 to 575286
    request('https://dl.filla.be/aiTJodJ_k')
      .pipe(
        through2((chunk, enc, cb) => {
          console.log('writing chunk');
          res.write(sideband(chunk));
          cb();
        })
      )
      .on('finish', () => {
        console.log('finish');
        done();
      });
  });

  console.log('push accepted');
  push.accept();
});

http
  .createServer((req, res) => {
    repos.handle(req, res);
  })
  .listen(8000);