Manpages - sd_watchdog_enabled.3

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

  #include <systemd/sd-daemon.h>

int sd_watchdog_enabled(int */unset_environment/, uint64_t */usec/);*

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.

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.

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.

$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.

$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.

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