sd_watchdog_enabled(3) — Linux manual page


SD_WATCHDOG_ENABLED(3)       sd_watchdog_enabled      SD_WATCHDOG_ENABLED(3)

NAME         top

       sd_watchdog_enabled - Check whether the service manager expects
       watchdog keep-alive notifications from a service

SYNOPSIS         top

       #include <systemd/sd-daemon.h>

       int sd_watchdog_enabled(int unset_environment, uint64_t *usec);

DESCRIPTION         top

       sd_watchdog_enabled() may be called by a service to detect whether
       the service manager expects regular keep-alive watchdog notification
       events from it, and the timeout after which the manager will act on
       the service if it did not get such a notification.

       If the $WATCHDOG_USEC environment variable is set, and the
       $WATCHDOG_PID variable is unset or set to the PID of the current
       process, the service manager expects notifications from this process.
       The manager will usually terminate a service when it does not get a
       notification message within the specified time after startup and
       after each previous message. It is recommended that a daemon sends a
       keep-alive notification message to the service manager every half of
       the time returned here. Notification messages may be sent with
       sd_notify(3) with a message string of "WATCHDOG=1".

       If the unset_environment parameter is non-zero, sd_watchdog_enabled()
       will unset the $WATCHDOG_USEC and $WATCHDOG_PID environment variables
       before returning (regardless of whether the function call itself
       succeeded or not). Those variables are no longer inherited by child
       processes. Further calls to sd_watchdog_enabled() will also return
       with zero.

       If the usec parameter is non-NULL, sd_watchdog_enabled() will write
       the timeout in µs for the watchdog logic to it.

       To enable service supervision with the watchdog logic, use
       WatchdogSec= in service files. See systemd.service(5) for details.

       Use sd_event_set_watchdog(3) to enable automatic watchdog support in
       sd-event(3)-based event loops.

RETURN VALUE         top

       On failure, this call returns a negative errno-style error code. If
       the service manager expects watchdog keep-alive notification messages
       to be sent, > 0 is returned, otherwise 0 is returned. Only if the
       return value is > 0, the usec parameter is valid after the call.

NOTES         top

       These APIs are implemented as a shared library, which can be compiled
       and linked to with the libsystemd pkg-config(1) file.

       Internally, this function parses the $WATCHDOG_PID and $WATCHDOG_USEC
       environment variable. The call will ignore these variables if
       $WATCHDOG_PID does not contain the PID of the current process, under
       the assumption that in that case, the variables were set for a
       different process further up the process tree.

ENVIRONMENT         top

           Set by the system manager for supervised process for which
           watchdog support is enabled, and contains the PID of that
           process. See above for details.

           Set by the system manager for supervised process for which
           watchdog support is enabled, and contains the watchdog timeout in
           µs. See above for details.

SEE ALSO         top

       systemd(1), sd-daemon(3), daemon(7), systemd.service(5),
       sd_notify(3), sd_event_set_watchdog(3)

COLOPHON         top

       This page is part of the systemd (systemd system and service manager)
       project.  Information about the project can be found at 
       ⟨⟩.  If you have a bug
       report for this manual page, see
       ⟨⟩.  This
       page was obtained from the project's upstream Git repository
       ⟨⟩ on 2020-09-18.  (At that
       time, the date of the most recent commit that was found in the repos‐
       itory was 2020-09-18.)  If you discover any rendering problems in
       this HTML version of the page, or you believe there is a better or
       more up-to-date source for the page, or you have corrections or
       improvements to the information in this COLOPHON (which is not part
       of the original manual page), send a mail to

systemd 246                                           SD_WATCHDOG_ENABLED(3)

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