SD_WATCHDOG_ENABLED(3)sd_watchdog_enabledSD_WATCHDOG_ENABLED(3)NAMEsd_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, const uint64_t *usec);
DESCRIPTIONsd_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 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). Further calls to sd_watchdog_enabled() will then
return with zero, but the variable is no longer inherited by child
processes.
If the usec parameter is non-NULL, sd_watchdog_enabled() will return
the timeout in µs for the watchdog logic. The service manager will
usually terminate a service when it did 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".
To enable service supervision with the watchdog logic, use WatchdogSec=
in service files. See systemd.service(5) for details.
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 functions parses the $WATCHDOG_PID and $WATCHDOG_USEC
environment variable. The call will ignore these variables if
$WATCHDOG_PID does containe 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 ALSOsystemd(1), sd-daemon(3), daemon(7), systemd.service(5), sd_notify(3)systemd 212SD_WATCHDOG_ENABLED(3)
