From 0ea8f5dacfb6d6bfba4dd4be86416bdd2dc5907d Mon Sep 17 00:00:00 2001 From: Eric Wong Date: Sun, 30 Jun 2019 07:11:00 +0000 Subject: examples/*@.service: sockets MUST be NonBlocking For users running multiple (-nntpd@1, -nntpd@2) instances of either -httpd or -nntpd via systemd to implement zero-downtime restarts; it's possible for a listen socket to become blocking for a moment during an accept syscall and cause a daemons to get stuck in a blocking accept() during PublicInbox::Listener::event_step (event_read in previous versions). Since O_NONBLOCK is a file description flag, systemd clearing O_NONBLOCK momentarily (before PublicInbox::Listener::new re-enables it) creates a window for another instance of our daemon to get stuck in accept(). cf. systemd.service(5) --- examples/unsubscribe-psgi@.service | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'examples/unsubscribe-psgi@.service') diff --git a/examples/unsubscribe-psgi@.service b/examples/unsubscribe-psgi@.service index acc29e8e..c8721fbe 100644 --- a/examples/unsubscribe-psgi@.service +++ b/examples/unsubscribe-psgi@.service @@ -12,7 +12,12 @@ After = unsubscribe-psgi.socket # any PSGI server ought to work, # but public-inbox-httpd supports socket activation like unsubscribe.milter ExecStart = /usr/local/bin/public-inbox-httpd -W0 /etc/unsubscribe.psgi + +# NonBlocking is REQUIRED to avoid a race condition if running +# simultaneous services +NonBlocking = true Sockets = unsubscribe-psgi.socket + # we need to modify the mlmmj spool User = mlmmj KillMode = process -- cgit v1.2.3-24-ge0c7