x SuSE Linux 13.1-RELEASE x
x SuSE Linux 13.1-RELEASEx
SD_WATCHDOG_ENABLED(3) sd_watchdog_enabled SD_WATCHDOG_ENABLED(3)
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 <mu>s 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
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.
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 <mu>s. See
above for details.
SEE ALSO
systemd(1), sd-daemon(3), daemon(7), systemd.service(5), sd_notify(3),
sd_event_set_watchdog(3)
systemd 254 SD_WATCHDOG_ENABLED(3)
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