Replace another use of temp files for named sockets on linux

Also prevent the multiprocessing module from calling unlink() on
abstract named sockets.

src/calibre/utils/ipc/server.py

@@ -86,19 +86,32 @@ class CriticalError(Exception):
 
 _name_counter = 0
 
-def create_linux_listener(authkey, backlog=4):
-    # Use abstract named sockets on linux to avoid creating unnecessary temp files
-    global _name_counter
-    prefix = u'\0calibre-ipc-listener-%d-%%d' % os.getpid()
-    while True:
-        _name_counter += 1
-        address = (prefix % _name_counter).encode('ascii')
-        try:
-            return address, Listener(address=address, authkey=authkey, backlog=backlog)
-        except EnvironmentError as err:
-            if err.errno == errno.EADDRINUSE:
-                continue
-            raise
+if islinux:
+    def create_listener(authkey, backlog=4):
+        # Use abstract named sockets on linux to avoid creating unnecessary temp files
+        global _name_counter
+        prefix = u'\0calibre-ipc-listener-%d-%%d' % os.getpid()
+        while True:
+            _name_counter += 1
+            address = (prefix % _name_counter).encode('ascii')
+            try:
+                l = Listener(address=address, authkey=authkey, backlog=backlog)
+                if hasattr(l._listener._unlink, 'cancel'):
+                    # multiprocessing tries to call unlink even on abstract
+                    # named sockets, prevent it from doing so.
+                    l._listener._unlink.cancel()
+                return address, l
+            except EnvironmentError as err:
+                if err.errno == errno.EADDRINUSE:
+                    continue
+                raise
+else:
+    def create_listener(authkey, backlog=4):
+        address = arbitrary_address('AF_PIPE' if iswindows else 'AF_UNIX')
+        if iswindows and address[1] == ':':
+            address = address[2:]
+        listener = Listener(address=address, authkey=authkey, backlog=backlog)
+        return address, listener
 
 class Server(Thread):
 
@@ -115,13 +128,7 @@ class Server(Thread):
         self.pool_size = limit if pool_size is None else pool_size
         self.notify_on_job_done = notify_on_job_done
         self.auth_key = os.urandom(32)
-        if islinux:
-            self.address, self.listener = create_linux_listener(self.auth_key, backlog=4)
-        else:
-            self.address = arbitrary_address('AF_PIPE' if iswindows else 'AF_UNIX')
-            if iswindows and self.address[1] == ':':
-                self.address = self.address[2:]
-            self.listener = Listener(address=self.address, authkey=self.auth_key, backlog=4)
+        self.address, self.listener = create_listener(self.auth_key, backlog=4)
         self.add_jobs_queue, self.changed_jobs_queue = Queue(), Queue()
         self.kill_queue = Queue()
         self.waiting_jobs = []

src/calibre/utils/ipc/simple_worker.py

@@ -9,7 +9,7 @@ __docformat__ = 'restructuredtext en'
 
 import os, cPickle, traceback, time, importlib
 from binascii import hexlify, unhexlify
-from multiprocessing.connection import Listener, arbitrary_address, Client
+from multiprocessing.connection import Client
 from threading import Thread
 from contextlib import closing
 
@@ -117,11 +117,9 @@ def communicate(ans, worker, listener, args, timeout=300, heartbeat=None,
     ans['result'] = cw.res['result']
 
 def create_worker(env, priority='normal', cwd=None, func='main'):
-    address = arbitrary_address('AF_PIPE' if iswindows else 'AF_UNIX')
-    if iswindows and address[1] == ':':
-        address = address[2:]
+    from calibre.utils.ipc.server import create_listener
     auth_key = os.urandom(32)
-    listener = Listener(address=address, authkey=auth_key)
+    address, listener = create_listener(auth_key)
 
     env = dict(env)
     env.update({