sd_watchdog_enabled

systemd
Developer Lennart Poettering lennart@poettering.net
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

## 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

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.

`$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.

## See Also

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