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630eddbbbc
With default KillMode=control-group, systemd will send signals to all
processes in cgroup and this will lead to server will be terminated
forcefully due to double signal.
2023.09.19 12:47:06.369090 [ 763 ] {} <Information> Application: Received termination signal (Terminated)
2023.09.19 12:47:06.369141 [ 762 ] {} <Debug> Application: Received termination signal.
2023.09.19 12:47:06.369215 [ 763 ] {} <Information> Application: Received termination signal (Terminated)
2023.09.19 12:47:06.369225 [ 763 ] {} <Information> Application: This is the second termination signal. Immediately terminate.
2023.09.19 12:47:06.400959 [ 761 ] {} <Information> Application: Child process exited normally with code 143.
Someone may naively think that, hey, I can change KillMode to
process/mixed, but this will not work either, because in this case
systemd cannot wait for the $MainPID (and main_pid_alien=true in
systemd's sources), because it is not a child of systemd, and this will
lead to double signal again:
2023.09.19 16:24:19.694473 [ 3118 ] {} <Information> Application: Received termination signal (Terminated)
2023.09.19 16:24:19.694894 [ 3118 ] {} <Information> Application: Received termination signal (Terminated)
2023.09.19 16:24:19.695060 [ 3118 ] {} <Information> Application: This is the second termination signal. Immediately terminate.
And this is because it sends signal firstly on a normal termnation and
then when it cleans up left over processes:
clickhouse-server.service: Found left-over process 3117 (clickhouse-serv) in control group while starting unit. Ignoring.
And yes, even though it prints "Ignoring" here (I guess it is related to
the fact that it can be ignored if the signal will not be handled)
Here is a proof of double signal by systemd:
# pgrep clickhouse-serv | xargs strace -e /kill -fp
strace: Process 3117 attached with 469 threads
[pid 3582] --- SIGTERM {si_signo=SIGTERM, si_code=SI_USER, si_pid=1, si_uid=0} ---
[pid 3580] --- SIGCONT {si_signo=SIGCONT, si_code=SI_USER, si_pid=1, si_uid=0} ---
[pid 3582] --- SIGCONT {si_signo=SIGCONT, si_code=SI_USER, si_pid=1, si_uid=0} ---
[pid 3580] --- SIGTERM {si_signo=SIGTERM, si_code=SI_USER, si_pid=1, si_uid=0} ---
^^^
[pid 3118] tgkill(3117, 3118, SIGTERM) = 0 # and this is a force termination
So yes, there is no other way except for disabling signal forwarding.
*Well, there is another way, but I guess it is will be unwelcome (even
though systemd can be configured in multiple ways right now, and there
is even systemd-oomd instead of clickhouse'es watchdog) - disable
watchdog completelly.*
Signed-off-by: Azat Khuzhin <a.khuzhin@semrush.com>
44 lines
1.8 KiB
Desktop File
44 lines
1.8 KiB
Desktop File
[Unit]
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Description=ClickHouse Server (analytic DBMS for big data)
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Requires=network-online.target
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# NOTE: that After/Wants=time-sync.target is not enough, you need to ensure
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# that the time was adjusted already, if you use systemd-timesyncd you are
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# safe, but if you use ntp or some other daemon, you should configure it
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# additionaly.
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After=time-sync.target network-online.target
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Wants=time-sync.target
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[Service]
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Type=notify
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# NOTE: we leave clickhouse watchdog process enabled to be able to see OOM/SIGKILL traces in clickhouse-server.log files.
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# If you wish to disable the watchdog and rely on systemd logs just add "Environment=CLICKHOUSE_WATCHDOG_ENABLE=0" line.
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User=clickhouse
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Group=clickhouse
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Restart=always
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RestartSec=30
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# The following ClickHouse directives should be used instead of forcing SIGKILL by systemd:
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# - shutdown_wait_unfinished_queries
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# - shutdown_wait_unfinished
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TimeoutStopSec=infinity
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# Disable forwarding signals by watchdog, since with default systemd's
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# kill-mode control-group, systemd will send signal to all process in cgroup.
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Environment=CLICKHOUSE_WATCHDOG_NO_FORWARD=1
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# Since ClickHouse is systemd aware default 1m30sec may not be enough
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TimeoutStartSec=0
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# %p is resolved to the systemd unit name
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RuntimeDirectory=%p
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ExecStart=/usr/bin/clickhouse-server --config=/etc/clickhouse-server/config.xml --pid-file=%t/%p/%p.pid
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# Minus means that this file is optional.
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EnvironmentFile=-/etc/default/%p
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# Bring back /etc/default/clickhouse for backward compatibility
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EnvironmentFile=-/etc/default/clickhouse
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LimitCORE=infinity
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LimitNOFILE=500000
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CapabilityBoundingSet=CAP_NET_ADMIN CAP_IPC_LOCK CAP_SYS_NICE CAP_NET_BIND_SERVICE
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AmbientCapabilities=CAP_NET_ADMIN CAP_IPC_LOCK CAP_SYS_NICE CAP_NET_BIND_SERVICE
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[Install]
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# ClickHouse should not start from the rescue shell (rescue.target).
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WantedBy=multi-user.target
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