sd_event_set_watchdog

SD_EVENT_SET_WATCHDOG(3)      sd_event_set_watchdog     SD_EVENT_SET_WATCHDOG(3)



NAME
       sd_event_set_watchdog, sd_event_get_watchdog - Enable event loop watchdog
       support

SYNOPSIS
       #include <systemd/sd-event.h>

       int sd_event_set_watchdog(sd_event *event, int b);

       int sd_event_get_watchdog(sd_event *event);

DESCRIPTION
       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
       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.

   Errors
       Returned errors may indicate the following problems:

       -ECHILD
           The event loop has been created in a different process.

       -EINVAL
           The passed event loop object was invalid.

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

SEE ALSO
       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)



systemd 247                                             SD_EVENT_SET_WATCHDOG(3)