On Fri, 9 Mar 2018 09:25:10 -0800, Gregory Szorc wrote: > If you have this stdio stuff paged into your brain, you may want to look at > hook.py and what it is doing with stdio. Essentially, it is doing dup() and > dup2() to temporarily redirect stdout to stderr such that the wire protocol > can intercept output and forward it to the wire protocol client (or the > CLI).
and hook output never be interleaved into the wire protocol channel. > See hook.redirect(True) in the wire protocol server code and follow > the trail from there. > > In the case of shell hooks, I believe those processes inherit the parent's > file descriptors. Which after hook.py mucks with the file descriptors, is > actually the stderr stream. I think these dup()s are no longer needed for shell hooks since a subprocess output is sent to ui.fout which is actually ui.ferr in ssh session. They're still valid for in-process hooks, though. > I question the appropriateness of the approach. I think it would be better > to e.g. send ui.ferr to shell hooks and to temporarily muck with > sys.stdout/sys.stderr when running Python hooks. But this has implications > and I haven't thought it through. I'd *really* like to see us not have to > do the dup()/dup2() dance in the hooks because that is mucking with global > state and can make it hard to debug server processes. Yeah. I doubt if the current code would work well in threaded hgweb. I think we can do a similar trick to commandserver, which basically nullifes the global sys.stdin/stdout to protect IPC channels from being corrupted by third-party extensions, and use ui.fin/fout thoroughly. https://www.mercurial-scm.org/repo/hg/file/4.5.2/mercurial/commandserver.py#l334 Regarding the wire protocol and hooks, this means: - do dup()/dup2() business globally, not locally in hook.py - isolate wire-protocol streams from ui.fin/fout (ssh-wire: dup()ed stdin/stdout, ui.fin -> stdin -> null, stdout -> null, ui.fout -> ui.ferr -> stderr) - in-process hook must use ui instead of print() because print()s will be sent to /dev/null - shell hook output is redirected to stderr as long as ui.fout points to stderr (the stderr will be dup()ed to stdout after fork) _______________________________________________ Mercurial-devel mailing list Mercurial-devel@mercurial-scm.org https://www.mercurial-scm.org/mailman/listinfo/mercurial-devel
