commit: 6e1ca591c2dacde806a277773d16b603558b04a2
Author: Anthony G. Basile <blueness <AT> gentoo <DOT> org>
AuthorDate: Fri Jul 10 02:40:09 2015 +0000
Commit: Anthony G. Basile <blueness <AT> gentoo <DOT> org>
CommitDate: Fri Jul 10 02:40:09 2015 +0000
URL: https://gitweb.gentoo.org/proj/grss.git/commit/?id=6e1ca591
grs/Daemon.py: document.
grs/Daemon.py | 37 ++++++++++++++++++++++++++++++-------
1 file changed, 30 insertions(+), 7 deletions(-)
diff --git a/grs/Daemon.py b/grs/Daemon.py
index 15290a5..0d2d988 100644
--- a/grs/Daemon.py
+++ b/grs/Daemon.py
@@ -7,22 +7,31 @@ import sys
import time
class Daemon:
- """ doc here
- more doc
- Adopted from Sander Marechal's "A simple unix/linux daemon in Python"
+ """ Adopted from Sander Marechal's "A simple unix/linux daemon in Python"
See:
http://www.jejik.com/articles/2007/02/a_simple_unix_linux_daemon_in_python/
+
+ To use, inherit by a subclass which overrides run() and does all the
+ daemon work. You start the daemon with
+
+ d = MyDaemon(pidfile, foo='1', bar='2') # Any number for kwargs
after pidfile
+ d.start() # to start the daemon
+ d.restart() # to restart the daemon
+ d.stop() # to stop the daemon
+
+ Note: This isn't completely general daemon code as it doesn't close
stdout/stderr.
+ Rather these are redirected to /var/log/grs/grs-daemon-<pid>.err to
capture any
+ exceptions for debugging.
"""
def __init__(self, pidfile, **kwargs):
+ """ Since this will be used as a super class, we'll accept any **kwargs
+ and insert them to our internal __dict__.
+ """
self.pidfile = pidfile
for k in kwargs:
self.__dict__[k] = kwargs[k]
def daemonize(self):
- """ doc here
- more doc
- """
-
try:
pid = os.fork()
if pid > 0:
@@ -55,6 +64,9 @@ class Daemon:
sys.stderr.flush()
os.dup2(se.fileno(), sys.stderr.fileno())
+ # Use atexit to remove the pidfile when we shutdown.
+ # No matter where the exit is initiated, eg from Execute.py
+ # we are sure that atexit() will run and delete the pidfile.
atexit.register(self.delpid)
with open(self.pidfile,'w') as pf:
pf.write('%d\n' % os.getpid())
@@ -65,6 +77,10 @@ class Daemon:
def start(self):
+ # If there's a pidfile when we try to startup, then either
+ # its stale or we're already running. If the pidfile is stale,
+ # remove it and startup as usual. If we're already running,
+ # then don't start a second instance.
try:
with open(self.pidfile, 'r') as pf:
pid = int(pf.read().strip())
@@ -84,6 +100,13 @@ class Daemon:
def stop(self):
+ # Try to open our pidfile and read our pid. If you have a pid but
+ # there is no process at that pid, then we're not running and all
+ # we have to do is cleanup our stale pidfile.a If we can't get a
+ # pid from our pidfile, then we've lost the original process. Either
+ # it crashed or something else killed the pidfile. We don't know.
+ # Finally if have a valid pid, send it a bunch of SIGTERMS followed
+ # by SIGKILLS just in case.
try:
with open(self.pidfile,'r') as pf:
pid = int(pf.read().strip())
