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105 lines
2.7 KiB
Python
105 lines
2.7 KiB
Python
#!/usr/bin/env python3
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# SPDX-License-Identifier: MIT-0
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#
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# Implement the systemd notify protocol without external dependencies.
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# Supports both readiness notification on startup and on reloading,
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# according to the protocol defined at:
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# https://www.freedesktop.org/software/systemd/man/latest/sd_notify.html
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# This protocol is guaranteed to be stable as per:
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# https://systemd.io/PORTABILITY_AND_STABILITY/
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import errno
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import os
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import signal
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import socket
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import sys
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import time
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reloading = False
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terminating = False
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def notify(message):
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if not message:
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raise ValueError("notify() requires a message")
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socket_path = os.environ.get("NOTIFY_SOCKET")
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if not socket_path:
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return
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if socket_path[0] not in ("/", "@"):
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raise OSError(errno.EAFNOSUPPORT, "Unsupported socket type")
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# Handle abstract socket.
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if socket_path[0] == "@":
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socket_path = "\0" + socket_path[1:]
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with socket.socket(socket.AF_UNIX, socket.SOCK_DGRAM | socket.SOCK_CLOEXEC) as sock:
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sock.connect(socket_path)
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sock.sendall(message)
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def notify_ready():
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notify(b"READY=1")
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def notify_reloading():
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microsecs = time.clock_gettime_ns(time.CLOCK_MONOTONIC) // 1000
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notify(f"RELOADING=1\nMONOTONIC_USEC={microsecs}".encode())
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def notify_stopping():
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notify(b"STOPPING=1")
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def reload(signum, frame):
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global reloading
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reloading = True
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def terminate(signum, frame):
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global terminating
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terminating = True
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def main():
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print("Doing initial setup")
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global reloading, terminating
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# Set up signal handlers.
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print("Setting up signal handlers")
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signal.signal(signal.SIGHUP, reload)
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signal.signal(signal.SIGINT, terminate)
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signal.signal(signal.SIGTERM, terminate)
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# Do any other setup work here.
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# Once all setup is done, signal readiness.
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print("Done setting up")
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notify_ready()
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print("Starting loop")
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while not terminating:
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if reloading:
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print("Reloading")
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reloading = False
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# Support notifying the manager when reloading configuration.
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# This allows accurate state tracking as well as automatically
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# enabling 'systemctl reload' without needing to manually
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# specify an ExecReload= line in the unit file.
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notify_reloading()
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# Do some reconfiguration work here.
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print("Done reloading")
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notify_ready()
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# Do the real work here ...
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print("Sleeping for five seconds")
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time.sleep(5)
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print("Terminating")
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notify_stopping()
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if __name__ == "__main__":
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sys.stdout.reconfigure(line_buffering=True)
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print("Starting app")
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main()
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print("Stopped app")
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