* [PATCH] examples/unicorn@.service: note the NonBlocking flag
@ 2019-07-03 23:34 Eric Wong
0 siblings, 0 replies; only message in thread
From: Eric Wong @ 2019-07-03 23:34 UTC (permalink / raw)
To: unicorn-public
It's racy otherwise when starting simultaneous instanced units.
Without specifying NonBlocking=true, systemd will clear the
O_NONBLOCK flag every time it starts a new service instance.
There's a small window where systemd can clear O_NONBLOCK
immediately after it's set by Ruby (or kgio):
unicorn@1 |systemd |unicorn@2
---------------------------+----------------+--------------------
F_SETFL, O_NONBLOCK|O_RDWR | | (not running, yet)
|F_SETFL, O_RDWR |
|fork |
| exec unicorn@2 |
accept4(...) # blocks! | | (now started by systemd)
| |F_SETFL,O_NONBLOCK|O_RDWR
| |accept4(...) non-blocking
---
examples/unicorn@.service | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/examples/unicorn@.service b/examples/unicorn@.service
index d95eb83..946de44 100644
--- a/examples/unicorn@.service
+++ b/examples/unicorn@.service
@@ -14,7 +14,14 @@ After = unicorn.socket
# bundler users must use the "--keep-file-descriptors" switch, here:
# ExecStart = bundle exec --keep-file-descriptors unicorn -c ...
ExecStart = /usr/bin/unicorn -c /path/to/unicorn.conf.rb /path/to/config.ru
+
+# NonBlocking MUST be true if using socket activation with unicorn.
+# Otherwise, there's a small window in-between when the non-blocking
+# flag is set by us and our accept4 call where systemd can momentarily
+# make the socket blocking, causing us to block on accept4:
+NonBlocking = true
Sockets = unicorn.socket
+
KillSignal = SIGQUIT
User = nobody
Group = nogroup
--
EW
^ permalink raw reply related [flat|nested] only message in thread
only message in thread, other threads:[~2019-07-03 23:34 UTC | newest]
Thread overview: (only message) (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-07-03 23:34 [PATCH] examples/unicorn@.service: note the NonBlocking flag Eric Wong
Code repositories for project(s) associated with this public inbox
https://yhbt.net/unicorn.git/
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).