* [PATCH 0/2] warn on inheriting blocking sockets
@ 2019-06-30 22:19 5% Eric Wong
0 siblings, 0 replies; 2+ results
From: Eric Wong @ 2019-06-30 22:19 UTC (permalink / raw)
To: meta
A followup to https://public-inbox.org/meta/20190630074146.GA16199@dcvr/
("examples/*@.service: sockets MUST be NonBlocking")
1/2 is a long-needed cleanup patch, 2/2 is what matters to users.
Yeah, I'm shocked it's taken as long as it has to notice this
oversight, I completely missed that systemd would clear O_NONBLOCK
before spawning new instances.
I kinda wish accept4 would take SOCK_DONTWAIT (and maybe
SOCK_MUSTWAIT), but I also don't want to bloat the kernel
even more.
Eric Wong (2):
tests: common tcp_server and unix_server helpers
daemon: warn on inheriting blocking listeners
lib/PublicInbox/Daemon.pm | 10 +++++++++-
lib/PublicInbox/Listener.pm | 1 -
t/common.perl | 21 +++++++++++++++++++++
t/git-http-backend.t | 9 +--------
t/httpd-corner.t | 15 ++-------------
t/httpd-https.t | 9 +--------
t/httpd.t | 10 +---------
t/nntpd-tls.t | 11 ++---------
t/nntpd.t | 10 ++--------
t/perf-nntpd.t | 9 +--------
t/v2mirror.t | 8 +-------
t/v2writable.t | 9 +--------
t/www_listing.t | 9 +--------
13 files changed, 43 insertions(+), 88 deletions(-)
--
EW
^ permalink raw reply [relevance 5%]
* [PATCH] examples/*@.service: sockets MUST be NonBlocking
@ 2019-06-30 7:41 7% Eric Wong
0 siblings, 0 replies; 2+ results
From: Eric Wong @ 2019-06-30 7:41 UTC (permalink / raw)
To: meta
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)
---
Additional warnings and tests for this race coming;
but I need food + sleep.
I kinda wished I'd pushed for accept4(..., SOCK_DONTWAIT):
https://lore.kernel.org/lkml/20150513023712.GA4206@dcvr.yhbt.net/
examples/public-inbox-httpd@.service | 5 +++++
examples/public-inbox-nntpd@.service | 5 +++++
examples/unsubscribe-psgi@.service | 5 +++++
3 files changed, 15 insertions(+)
diff --git a/examples/public-inbox-httpd@.service b/examples/public-inbox-httpd@.service
index 56117ef..e811da4 100644
--- a/examples/public-inbox-httpd@.service
+++ b/examples/public-inbox-httpd@.service
@@ -20,7 +20,12 @@ ExecStartPre = /bin/mkdir -p -m 1777 /tmp/.pub-inline
ExecStart = /usr/local/bin/public-inbox-httpd \
-1 /var/log/public-inbox/httpd.out.log
StandardError = syslog
+
+# NonBlocking is REQUIRED to avoid a race condition if running
+# simultaneous services
+NonBlocking = true
Sockets = public-inbox-httpd.socket
+
KillSignal = SIGQUIT
User = nobody
Group = nogroup
diff --git a/examples/public-inbox-nntpd@.service b/examples/public-inbox-nntpd@.service
index 62202c2..a879841 100644
--- a/examples/public-inbox-nntpd@.service
+++ b/examples/public-inbox-nntpd@.service
@@ -20,7 +20,12 @@ ExecStartPre = /bin/mkdir -p -m 1777 /tmp/.pub-inline
ExecStart = /usr/local/bin/public-inbox-nntpd \
-1 /var/log/public-inbox/nntpd.out.log
StandardError = syslog
+
+# NonBlocking is REQUIRED to avoid a race condition if running
+# simultaneous services
+NonBlocking = true
Sockets = public-inbox-nntpd.socket
+
KillSignal = SIGQUIT
User = nobody
Group = nogroup
diff --git a/examples/unsubscribe-psgi@.service b/examples/unsubscribe-psgi@.service
index acc29e8..c8721fb 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
--
EW
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2019-06-30 22:19 5% [PATCH 0/2] warn on inheriting blocking sockets Eric Wong
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