[systemd-devel] Different behaviour when sending SIGTERM

[Marcos Mello]

Squid is known to be borked when running as a daemon (background):

http://bugs.squid-cache.org/show_bug.cgi?id=3826#c12

But still I am experiencing a difference between systemd's "built in" signal
delivery and systemctl kill.

# systemctl -l status squid.service
* squid.service - Squid Web Proxy Server
   Loaded: loaded (/etc/systemd/system/squid.service; disabled)
   Active: active (running) since Sun 2015-03-29 15:21:16 BRT; 20s ago
  Process: 1488 ExecStart=/usr/sbin/squid $SQUID_OPTS (code=exited,
status=0/SUCCESS)
 Main PID: 1491 (squid)
   CGroup: /system.slice/squid.service
           |-1489 /usr/sbin/squid -sX
           |-1491 (squid-1) -sX
           |-1492 (ssl_crtd) -s /var/lib/squid/ssl_db -M 4MB -b 4096
           |-1493 (ssl_crtd) -s /var/lib/squid/ssl_db -M 4MB -b 4096
           |-1494 (ssl_crtd) -s /var/lib/squid/ssl_db -M 4MB -b 4096
           |-1495 (ssl_crtd) -s /var/lib/squid/ssl_db -M 4MB -b 4096
           |-1496 (ssl_crtd) -s /var/lib/squid/ssl_db -M 4MB -b 4096
           `-1497 (logfile-daemon) /var/log/squid/access.log

Mar 29 15:21:16 xxx.localdomain squid[1491]: 0 Objects cancelled.
Mar 29 15:21:16 xxx.localdomain squid[1491]: 0 Duplicate URLs purged.
Mar 29 15:21:16 xxx.localdomain squid[1491]: 0 Swapfile clashes avoided.
Mar 29 15:21:16 xxx.localdomain squid[1491]: Took 0.23 seconds (  0.00
objects/sec).
Mar 29 15:21:16 xxx.localdomain squid[1491]: Beginning Validation Procedure
Mar 29 15:21:16 xxx.localdomain systemd[1]: squid.service: Supervising
process 1491 which is not our child. We'll most likely not notice when it exits.
Mar 29 15:21:16 xxx.localdomain squid[1491]: Completed Validation Procedure
Mar 29 15:21:16 xxx.localdomain squid[1491]: Validated 0 Entries
Mar 29 15:21:16 xxx.localdomain squid[1491]: store_swap_size = 0.00 KB
Mar 29 15:21:16 xxx.localdomain squid[1491]: storeLateRelease: released 0
objects

After 'systemctl stop squid.service':

# strace -f -e trace=process -p 1491
Process 1491 attached
+++ killed by SIGKILL +++

When I run 'systemctl kill --kill-who=main squid.service':

# strace -f -e trace=process -p 1510
Process 1510 attached
--- SIGTERM {si_signo=SIGTERM, si_code=SI_USER, si_pid=1, si_uid=0} ---
--- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_KILLED, si_pid=1516, si_uid=23,
si_status=SIGTERM, si_utime=0, si_stime=0} ---
wait4(-1, [{WIFSIGNALED(s) && WTERMSIG(s) == SIGTERM}], WNOHANG, NULL) = 1516
wait4(-1, 0x7ffd9ffe6624, WNOHANG, NULL) = 0
exit_group(0)                           = ?
+++ exited with 0 +++

The modified service file:

# /etc/systemd/system/squid.service
[Unit]
Description=Squid Web Proxy Server
After=network.target nss-lookup.target

[Service]
Type=forking
PIDFile=/run/squid.pid
EnvironmentFile=/etc/sysconfig/squid
#ExecStartPre=/usr/local/libexec/cache_swap.sh
ExecStart=/usr/sbin/squid $SQUID_OPTS
ExecReload=/usr/bin/kill -HUP $MAINPID
#ExecStop=/usr/sbin/squid -k shutdown
KillMode=process
SendSIGKILL=no

[Install]
WantedBy=multi-user.target

Reload works fine. 'squid -k shutdown' (it just sends SIGTERM to the pid
file process) works fine. Any clues? This is Fedora 21 (systemd-216-21)
running squid-3.4.12-2 from updates-testing.