проверить, ожидает ли диспетчер службы уведомлений об активности сторожевого таймера от службы (Check whether the service manager expects watchdog keep-alive notifications from a service)
Имя (Name)
sd_watchdog_enabled - Check whether the service manager expects
watchdog keep-alive notifications from a service
Синопсис (Synopsis)
#include <systemd/sd-daemon.h>
int sd_watchdog_enabled(int unset_environment, uint64_t *usec);
Описание (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.
Возвращаемое значение (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.
Примечание (Note)
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.
Окружение (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.
Смотри также (See also)
systemd(1), sd-daemon(3), daemon(7), systemd.service(5),
sd_notify(3), sd_event_set_watchdog(3)
