systemd_watchdog

sd_notify(3) and sd_watchdog_enabled(3) client functionality implemented in Python 3 for writing Python daemons

Install

$ pip install systemd-watchdog

or

$ git clone ...
$ make install

Usage

README_example.py

#!/bin/env python3
"""systemd_watchdog example."""

import time

import systemd_watchdog

wd = systemd_watchdog.WatchDog()
if not wd.is_enabled:
    # Then it's probably not running is systemd with watchdog enabled
    msg = "Watchdog not enabled"
    raise Exception(msg)  # noqa: TRY002

# Report a status message
wd.status("Starting my service...")
time.sleep(3)

# Report that the program init is complete
wd.ready()
wd.status("Init is complete...")
wd.notify()
time.sleep(3)

# Compute time between notifications
timeout_half_sec = int(float(wd.timeout) / 2e6)  # Convert us->s and half that
wd.status("Sleeping and then notify x 3")
time.sleep(timeout_half_sec)
wd.notify()
time.sleep(timeout_half_sec)
wd.notify()
time.sleep(timeout_half_sec)
wd.notify()
wd.status("Spamming loop - should only see 2-3 notifications")
t = float(0)
while t <= 4 * timeout_half_sec:
    time.sleep(0.05)
    wd.ping()
    t += 0.05

# Report an error to the service manager
wd.notify_error("An irrecoverable error occured!")
# The service manager will probably kill the program here
time.sleep(3)

Quick Example

In one terminal: socat unix-recv:/tmp/tempo.sock -

In another terminal: NOTIFY_SOCKET=/tmp/tempo.sock WATCHDOG_USEC=5000000 python3 README_example.py

Expected output (in first terminal):

STATUS=Starting my service...
READY=1
STATUS=Init is complete...
WATCHDOG=1
STATUS=Sleeping and then notify x 3
WATCHDOG=1
WATCHDOG=1
WATCHDOG=1
STATUS=Spamming loop - should only see 2-3 notifications
WATCHDOG=1
WATCHDOG=1
WATCHDOG=1
STATUS=An irrecoverable error occured!
WATCHDOG=trigger

Second Example

A second example, including the required systemd unit files, is included in the source on GitHub.

Public Interface

systemd_watchdog.WatchDog - commonly used properties and methods

ping

The only method required for the simplest implementation; combines notify_due with notify() to only send "alive" notifications at reasonable intervals.

Returns boolean indicating if a message was sent or not.

beat

Alias for ping() if you prefer heartbeat terminology.

ready()

Report ready service state, i.e. completed init (only needed with Type=notify).

status(msg)

Send a service status message.

systemd_watchdog.WatchDog - less-used properties and methods

is_enabled

Boolean property stating whether watchdog capability is enabled.

timeout

Property reporting the number of microseconds (int) before process will be killed.

It is recommended that you call notify() once roughly half of this interval has passed (see notify_due).

timeout_td

Property that is the same as timeout but presented as datetime.timedelta for easier manipulation.

notify_due

Boolean property indicating more than half of the watchdog interval has passed since last update.

notify()

Report a healthy service state. Other calls, e.g. status() do not reset the watchdog.

notify_error(msg=None)

Report an error to the watchdog manager. This program will likely be killed upon receipt.

If msg is provided, it will be reported as a status message prior to the error.

History

Aaron D. Marasco Aug 2025 (1.0.0, 1.0.1)

• Added typing
• Modernized build (pyproject.toml, poetry, etc)
• Renamed watchdog => WatchDog

Aaron D. Marasco May 2020 (0.9.0)

• Forked from the sd-notify project https://github.com/stigok/sd-notify
• Additional contributors can be found in GitHub repository history

License

See LICENSE file