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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | NOTES | ENVIRONMENT | HISTORY | SEE ALSO | COLOPHON |
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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.
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.
$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.
Added in version 209.
$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.
Added in version 209.
sd_watchdog_enabled() was added in version 209.
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 page was obtained from the project's upstream Git repository
⟨https://github.com/systemd/systemd.git⟩ on 2024-06-14. (At that
time, the date of the most recent commit that was found in the
repository was 2024-06-13.) If you discover any rendering
problems in this HTML version of the page, or you believe there
is a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
[email protected]
systemd 257~devel 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)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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