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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | NOTES | ENVIRONMENT | SEE ALSO | COLOPHON |
SD_WATCHDOG_ENABLED(3) sd_watchdog_enabled 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);
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.
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.
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.
$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.
systemd(1), sd-daemon(3), daemon(7), systemd.service(5),
sd_notify(3), sd_event_set_watchdog(3)
This page is part of the systemd (systemd system and service manager)
project. Information about the project can be found at
⟨http://www.freedesktop.org/wiki/Software/systemd⟩. If you have a bug
report for this manual page, see
⟨http://www.freedesktop.org/wiki/Software/systemd/#bugreports⟩. This
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COLOPHON (which is not part of the original manual page), send a mail
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systemd 234 SD_WATCHDOG_ENABLED(3)
Pages that refer to this page: sd-daemon(3), sd_event_set_watchdog(3), sd_notify(3), systemd.exec(5), systemd.service(5), systemd.directives(7), systemd.index(7)