Question

I am creating a small proprietary game server manager in Node.js; currently it runs the game by spawning via child_process:

var server = spawn(cmd, args, { cwd: 'something' });

So long as the manager continues to run I can pipe commands and deal with the child as I would like. However, consider the possibility that my manager crashes or is closed. How would I then reattach to the previously spawned child process (which was still running while the manager was down)? I can store pidfiles to try and reconnect based on pid; but I’m not sure how to get a child_process object with access to the child’s stdio objects.

I really would like this to be recoverable; any help is appreciated, thanks!

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Please note: The game servers are proprietary, some examples are Minecraft, Source DS, etc. Assume i do not have access to the sever source.

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EDIT

After reading some source code from node’s child_process it looks like if you specify a property in the options called stdinStream, stdoutStream, or stderrStream it should just open a socket to it. (See lines 428 – 496). So the issue then is, how do I stop spawn from actually doing a spawn and instead just settings its values based on a specified pid and streams I pass. (I would get my stdinStream by doing fs.createWriteStream('/proc/PID/fd/0'); which should work since that fd is created as a pipe.)

Answer 1

After speaking with some of the guys on the node project, it looks like the only way I can accomplish this is by dealing with the raw file descriptors in the proc fs. I will probably mock up something similar to a child_process object and create its streams like:

var child = {};
child.stdin = fs.createWriteStream('/proc/PID/fd/0');
child.stdout = fs.createReadStream('/proc/PID/fd/1');
child.stderr = fs.createReadStream('/proc/PID/fd/2');