re-create Unix domain sockets when binding,

to avoid losing the monitor on alternating restarts

src/zc/monitor/CHANGES.txt

@@ -2,11 +2,21 @@
 Change History
 ==============
 
+0.3.1 (2012-04-27)
+------------------
+
+- When binding the monitor to a Unix-domain socket, remove an existing
+  socket at the same path so the bind is successful.  This may affect
+  existing usage with respect to zopectl debug behavior, but will be
+  more predictable.
+
+
 0.3.0 (2011-12-12)
 ------------------
 
 - Added a simplified registration interface.
 
+
 0.2.1 (2011-12-10)
 ------------------
 
@@ -25,18 +35,21 @@ Change History
 
 - Add the "MORE" mode so commands can co-opt user interaction
 
+
 0.1.2 (2008-09-15)
 ------------------
 
 - Bugfix: The z3monitor server lacked a handle_close method, which
   caused errors to get logged when users closed connections before
   giving commands.
 
+
 0.1.1 (2008-09-14)
 ------------------
 
 - Bugfix: fixed and added test for regression in displaying tracebacks.
 
+
 0.1.0 (2008-09-14)
 ------------------
 

src/zc/monitor/__init__.py

@@ -14,7 +14,7 @@
 """Zope 3 Monitor Server
 """
 
-import errno, logging, traceback, socket
+import errno, logging, os, stat, traceback, socket
 
 import zope.component
 
@@ -91,6 +91,10 @@ def start(address):
     elif isinstance(address, basestring):
         #a unix domain socket string is passed
         ourAddress = address
+        if os.path.exists(ourAddress):
+            m = os.stat(ourAddress)
+            if stat.S_ISSOCK(m.st_mode):
+                os.unlink(ourAddress)
 
     try:
         global last_listener
@@ -99,6 +103,9 @@ def start(address):
         if e.args[0] == errno.EADDRINUSE:
             # Don't kill the process just because somebody else has our port.
             # This might be a zopectl debug or some other innocuous problem.
+            # (Existing Unix-domain sockets are removed before binding, so
+            # this doesn't work that way for those.  Use a separate offline
+            # configuration in that case.)
             logging.warning(
                 'unable to start zc.monitor server because the address %s '\
                 'is in use.',

src/zc/monitor/tests.py

@@ -13,9 +13,16 @@
 ##############################################################################
 
 import doctest
+import sys
+import unittest
 
 def test_suite():
-    return doctest.DocFileSuite(
-        'README.txt',
-        optionflags=doctest.NORMALIZE_WHITESPACE,
-        )
+    suite = unittest.TestSuite([
+        doctest.DocFileSuite(
+            'README.txt',
+            optionflags=doctest.NORMALIZE_WHITESPACE,
+            ),
+        ])
+    if not sys.platform.lower().startswith('win'):
+        suite.addTest(doctest.DocFileSuite('unix-sockets.txt'))
+    return suite

src/zc/monitor/unix-sockets.txt

@@ -0,0 +1,46 @@
+=========================
+Using Unix-domain sockets
+=========================
+
+Passing a string to start causes it to bind to a Unix-domain socket.
+
+Let's set up logging so we can see what's happening:
+
+    >>> import logging
+    >>> import os
+    >>> import stat
+    >>> import time
+    >>> import zc.monitor
+    >>> import zope.testing.loggingsupport
+
+    >>> loghandler = zope.testing.loggingsupport.InstalledHandler(
+    ...     None, level=logging.INFO)
+
+Passing a path as the argument to start causes a Unix socket to be bound:
+
+    >>> path = "testing.sock"
+
+    >>> zc.monitor.start(path)
+    'testing.sock'
+
+    >>> m1 = os.stat(path)
+    >>> stat.S_ISSOCK(m1.st_mode)
+    True
+
+Attempting to start the monitor at the same path again succeeds, but
+causes a new socket to be created:
+
+    >>> zc.monitor.start(path)
+    'testing.sock'
+
+    >>> m2 = os.stat(path)
+    >>> stat.S_ISSOCK(m2.st_mode)
+    True
+
+    >>> m1.st_ino == m2.st_ino
+    False
+
+Clean up:
+
+    >>> os.unlink(path)
+    >>> loghandler.uninstall()