Why is my Node child process that I created via spawn() hanging?

Question

I am using spawn() to make a git call. Sometimes it works fine but others it appears to be hanging. I see no events firing (error, exit, close) yet I see evidence that the process did in fact complete successfully.

var spawn = require('child_process').spawn;

spawn('git', ['push', 'origin', 'master'])
  .on('error', function(error) {
    console.log("ERROR: DETAILS: " + error);
  })
  .on('close', function(code) {
    console.log("SUCCESS: CODE: " + code);
  })
  .on('exit', function(code) {
    console.log("EXIT: CODE: " + code);
  })

Answer 1

As it turns out once the stderr buffer exceeds 24kb you must be reading from it or you not see any events for completion. Possible workarounds:

1. Set the stdio option on the spawn call.

   spawn('git', ['push', 'origin', 'master'], {stdio: 'ignore'});
   

   See Node ChildProcess doc for all of the possibilities - there are lots.

2. Add an on(data) handler.

   var git = spawn('git', ['push', 'origin', 'master']);
   ...
   git.stderr.on('data', function(data) {
     // do something with it
   });
   

3. Pipe it to stdout / stderr. This may be too verbose for your application but including it for completeness.

   var git = spawn('git', ['push', 'origin', 'master']);
   ...
   git.stderr.pipe(process.stderr);
   git.stdout.pipe(process.stdout);