[Zodb-checkins] CVS: ZODB3/zdaemon - zdrun.py:1.13.16.4

[Jeremy Hylton]

Update of /cvs-repository/ZODB3/zdaemon
In directory cvs.zope.org:/tmp/cvs-serv11418/zdaemon

Modified Files:
      Tag: Zope-2_7-branch
	zdrun.py 
Log Message:
Restore comment deleted by the merge of ZODB3-3_2-branch.


=== ZODB3/zdaemon/zdrun.py 1.13.16.3 => 1.13.16.4 ===
--- ZODB3/zdaemon/zdrun.py:1.13.16.3	Mon Sep 15 17:26:59 2003
+++ ZODB3/zdaemon/zdrun.py	Fri Sep 19 17:02:54 2003
@@ -317,6 +317,28 @@
             self.waitstatus = pid, sts
 
     def daemonize(self):
+
+        # To daemonize, we need to become the leader of our own session
+        # (process) group.  If we do not, signals sent to our
+        # parent process will also be sent to us.   This might be bad because
+        # signals such as SIGINT can be sent to our parent process during
+        # normal (uninteresting) operations such as when we press Ctrl-C in the
+        # parent terminal window to escape from a logtail command.
+        # To disassociate ourselves from our parent's session group we use
+        # os.setsid.  It means "set session id", which has the effect of
+        # disassociating a process from is current session and process group
+        # and setting itself up as a new session leader.
+        #
+        # Unfortunately we cannot call setsid if we're already a session group
+        # leader, so we use "fork" to make a copy of ourselves that is
+        # guaranteed to not be a session group leader.
+        #
+        # We also change directories, set stderr and stdout to null, and
+        # change our umask.
+        #
+        # This explanation was (gratefully) garnered from
+        # http://www.hawklord.uklinux.net/system/daemons/d3.htm
+
         pid = os.fork()
         if pid != 0:
             # Parent
@@ -563,7 +585,7 @@
                        "backoff=%r\n" % self.backoff +
                        "lasttime=%r\n" % self.proc.lasttime +
                        "application=%r\n" % self.proc.pid +
-                       "manager=%r\n" % os.getpid() +
+                       "manager=%r\n" % os.getpid() + 
                        "backofflimit=%r\n" % self.options.backofflimit +
                        "filename=%r\n" % self.proc.filename +
                        "args=%r\n" % self.proc.args)
@@ -631,7 +653,7 @@
 
 def decode_wait_status(sts):
     """Decode the status returned by wait() or waitpid().
-
+    
     Return a tuple (exitstatus, message) where exitstatus is the exit
     status, or -1 if the process was killed by a signal; and message
     is a message telling what happened.  It is the caller's
@@ -689,9 +711,9 @@
     return path
 
 # Main program
-
 def main(args=None):
     assert os.name == "posix", "This code makes many Unix-specific assumptions"
+
     zLOG.initialize()
     d = Daemonizer()
     d.main(args)