112 lines
3.6 KiB
Markdown
112 lines
3.6 KiB
Markdown
Using supervise-daemon
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======================
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Beginning with OpenRC-0.21 we have our own daemon supervisor,
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supervise-daemon., which can start a daemon and restart it if it
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terminates unexpectedly.
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The following is a brief guide on using this capability.
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* Use Default start, stop and status functions
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If you write your own start, stop and status functions in your service
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script, none of this will work. You must allow OpenRC to use the default
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functions.
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* Daemons must not fork
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Any daemon that you would like to have monitored by supervise-daemon
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must not fork. Instead, it must stay in the foreground. If the daemon
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forks, the supervisor will be unable to monitor it.
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If the daemon can be configured to not fork, this should be done in the
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daemon's configuration file, or by adding a command line option that
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instructs it not to fork to the command_args_foreground variable shown
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below.
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# Health Checks
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Health checks are a way to make sure a service monitored by
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supervise-daemon stays healthy. To configure a health check for a
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service, you need to write a healthcheck() function, and optionally an
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unhealthy() function in the service script. Also, you will need to set
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the healthcheck_timer and optionally healthcheck_delay variables.
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## healthcheck() function
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The healthcheck() function is run repeatedly based on the settings of
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the healthcheck_* variables. This function should return zero if the
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service is currently healthy or non-zero otherwise.
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## unhealthy() function
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If the healthcheck() function returns non-zero, the unhealthy() function
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is run, then the service is restarted. Since the service will be
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restarted by the supervisor, the unhealthy function should not try to
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restart it; the purpose of the function is to allow any cleanup tasks
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other than restarting the service to be run.
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# Variable Settings
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The most important setting is the supervisor variable. At the top of
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your service script, you should set this variable as follows:
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``` sh
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supervisor=supervise-daemon
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```
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Several other variables affect the way services behave under
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supervise-daemon. They are documented on the openrc-run man page, but I
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will list them here for convenience:
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``` sh
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command_args_foreground="arguments"
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```
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This should be used if the daemon you want to monitor
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forks and goes to the background by default. This should be set to the
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command line option that instructs the daemon to stay in the foreground.
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``` sh
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healthcheck_delay=seconds
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```
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This is the delay, in seconds, before the first health check is run.
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If it is not set, we use the value of healthcheck_timer.
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``` sh
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healthcheck_timer=seconds
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```
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This is the number of seconds between health checks. If it is not set,
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no health checks will be run.
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``` sh
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respawn_delay
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```
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This is the number of seconds to delay before attempting to respawn a
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supervised process after it dies unexpectedly.
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The default is to respawn immediately.
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``` sh
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respawn_max=x
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```
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This is the maximum number of times to respawn a supervised process
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during the given respawn period.
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The default is 10. 0 means unlimited.
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``` sh
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respawn_period=seconds
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```
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This works in conjunction with respawn_max and respawn_delay above to
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decide if a process should not be respawned for some reason.
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For example, if respawn period is 10 and respawn_max is 2, the process
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would need to die 3 times within 10 seconds to no longer be respawned.
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Note that respawn_delay will delay all of this, so in the above scenario
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a respawn_delay of greater than 5 will cause infinite respawns.
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By default, this is unset and respawn_max applies to the entire lifetime
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of the service.
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