On Sun, Jul 5, 2015 at 7:53 PM, Matt <hel...@gmail.com> wrote: > On Sun, Jul 5, 2015 at 6:12 PM, Sam Roberts <s...@strongloop.com> wrote: >> On Mon, Jun 29, 2015 at 10:37 AM, Matt <hel...@gmail.com> wrote: >> > You've exhausted the threadpool. Try setting the UV_THREADPOOL_SIZE env >> > var >> > higher and see if you can spawn more. >> >> Child processes don't go through the thread pool. >> >> The spawn is synchronous, the IPC (if any) on stdio is async, uses >> pipes, and goes through the epoll() event loop. > > > Are you sure? I haven't gone through the Node source, but I would assume > that the wait/waitpid calls can't be done without the thread pool. Of course > I could be entirely wrong about that, and the calls could just wait on the > closing of the fd instead. But it seemed like a logical conclusion.
I am sure. That it isn't async (in a thread pool) can be observed: child = cp.spawn(...) console.log(child.pid) prints a pid... but those two lines are sync, of course, there is no callback, right? Well, that means that the fork() at least must have happened synchronously, because until fork returns there is no pid. libuv actually blocks a bit longer than just the fork, it waits for the child to do exec, too, to guarantee the success of the exec, using a cool trick with pipes and close-on-exec, and that part of the process is nicely commented: https://github.com/libuv/libuv/blob/v1.x/src/unix/process.c#L422-L441 And you mention waitpid going through a thread pool, but it does not, waitpid() doesn't block (not as called by libuv, with WNOHANG), so it doesn't need to go through a thread pool. Also, even if it did, it would just mean that the maximum number of child processes that could be **waited on simultaneously** would be limited to the thread pool size, not that the maximum number of processes would be capped at that. Cheers, Sam -- http://StrongLoop.com makes it easy to develop APIs in Node, plus get DevOps capabilities like monitoring, debugging and clustering. -- Job board: http://jobs.nodejs.org/ New group rules: https://gist.github.com/othiym23/9886289#file-moderation-policy-md Old group rules: https://github.com/joyent/node/wiki/Mailing-List-Posting-Guidelines --- You received this message because you are subscribed to the Google Groups "nodejs" group. To unsubscribe from this group and stop receiving emails from it, send an email to nodejs+unsubscr...@googlegroups.com. To post to this group, send email to nodejs@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/nodejs/CACmrRmQ1rT1QLPNm9KN7xVZ9G98hEjTGGcyP3ijs5_PEF4%2B2Sg%40mail.gmail.com. For more options, visit https://groups.google.com/d/optout.
