sd_event_set_watchdog(3) — Linux manual page


SD_EVENT_SET_WATCHDOG(3)    sd_event_set_watchdog   SD_EVENT_SET_WATCHDOG(3)

NAME         top

       sd_event_set_watchdog, sd_event_get_watchdog - Enable event loop
       watchdog support

SYNOPSIS         top

       #include <systemd/sd-event.h>

       int sd_event_set_watchdog(sd_event *event, int b);

       int sd_event_get_watchdog(sd_event *event);

DESCRIPTION         top

       sd_event_set_watchdog() may be used to enable or disable automatic
       watchdog notification support in the event loop object specified in
       the event parameter. Specifically, depending on the b boolean
       argument this will make sure the event loop wakes up in regular
       intervals and sends watchdog notification messages to the service
       manager, if this was requested by the service manager. Watchdog
       support is determined with sd_watchdog_enabled(3), and watchdog
       messages are sent with sd_notify(3). See the WatchdogSec= setting in
       systemd.service(5) for details on how to enable watchdog support for
       a service and the protocol used. The wake-up interval is chosen as
       half the watchdog timeout declared by the service manager via the
       $WATCHDOG_USEC environment variable. If the service manager did not
       request watchdog notifications, or if the process was not invoked by
       the service manager this call with a true b parameter executes no
       operation. Passing a false b parameter will disable the automatic
       sending of watchdog notification messages if it was enabled before.
       Newly allocated event loop objects have this feature disabled.

       The first watchdog notification message is sent immediately when
       sd_event_set_watchdog() is invoked with a true b parameter.

       The watchdog logic is designed to allow the service manager to
       automatically detect services that ceased processing of incoming
       events, and thus appear "hung". Watchdog notifications are sent out
       only at the beginning of each event loop iteration. If an event
       source dispatch function blocks for an excessively long time and does
       not return execution to the event loop quickly, this might hence
       cause the notification message to be delayed, and possibly result in
       abnormal program termination, as configured in the service unit file.

       sd_event_get_watchdog() may be used to determine whether watchdog
       support was previously requested by a call to sd_event_set_watchdog()
       with a true b parameter and successfully enabled.

RETURN VALUE         top

       On success, sd_event_set_watchdog() and sd_event_get_watchdog()
       return a non-zero positive integer if the service manager requested
       watchdog support and watchdog support was successfully enabled. They
       return zero if the service manager did not request watchdog support,
       or if watchdog support was explicitly disabled with a false b
       parameter. On failure, they return a negative errno-style error code.

       Returned errors may indicate the following problems:

           The event loop has been created in a different process.

           The passed event loop object was invalid.

NOTES         top

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

SEE ALSO         top

       systemd(1), sd-event(3), sd_event_new(3), sd_event_add_io(3),
       sd_event_add_time(3), sd_event_add_signal(3), sd_event_add_child(3),
       sd_event_add_inotify(3), sd_event_add_defer(3),
       sd_watchdog_enabled(3), sd_notify(3), systemd.service(5)

COLOPHON         top

       This page is part of the systemd (systemd system and service manager)
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       ⟨⟩.  If you have a bug
       report for this manual page, see
       ⟨⟩.  This
       page was obtained from the project's upstream Git repository
       ⟨⟩ on 2020-08-13.  (At that
       time, the date of the most recent commit that was found in the repos‐
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systemd 246                                         SD_EVENT_SET_WATCHDOG(3)

Pages that refer to this page: sd-event(3)sd_watchdog_enabled(3)systemd.service(5)30-systemd-environment-d-generator(7)systemd.directives(7)systemd.index(7)