sd_watchdog_enabled

Index · Directives systemd 234

## Name

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

## Synopsis

    #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

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.

## 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)