sd_watchdog_enabled - Man Page

#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​.

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​.

$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​.

sd_watchdog_enabled() was added in version 209​.

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