sd_watchdog_enabled(3) — Linux manual page

SD_WATCHDOG_ENABLED(3)     sd_watchdog_enabled    SD_WATCHDOG_ENABLED(3)

NAME

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

SYNOPSIS

       #include <systemd/sd-daemon.h>

       int sd_watchdog_enabled(int unset_environment, uint64_t *usec);

DESCRIPTION

       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

       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

       Functions described here are available as a shared library, which
       can be compiled against and linked to with the
       libsystemd pkg-config(1) file.

       The code described here uses getenv(3), which is declared to be
       not multi-thread-safe. This means that the code calling the
       functions described here must not call setenv(3) from a parallel
       thread. It is recommended to only do calls to setenv() from an
       early phase of the program when no other threads have been
       started.

       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

       $WATCHDOG_PID
           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.

           Added in version 209.

       $WATCHDOG_USEC
           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.

           Added in version 209.

HISTORY

       sd_watchdog_enabled() was added in version 209.

SEE ALSO

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

COLOPHON

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       manager) project.  Information about the project can be found at
       ⟨http://www.freedesktop.org/wiki/Software/systemd⟩.  If you have
       a bug report for this manual page, see
       ⟨http://www.freedesktop.org/wiki/Software/systemd/#bugreports⟩.
       This page was obtained from the project's upstream Git repository
       ⟨https://github.com/systemd/systemd.git⟩ on 2024-06-14.  (At that
       time, the date of the most recent commit that was found in the
       repository was 2024-06-13.)  If you discover any rendering
       problems in this HTML version of the page, or you believe there
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       (which is not part of the original manual page), send a mail to
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systemd 257~devel                                 SD_WATCHDOG_ENABLED(3)

Pages that refer to this page: sd-daemon(3), sd_event_set_watchdog(3), sd_notify(3), systemd.exec(5), systemd.service(5), systemd.directives(7), systemd.index(7)

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