*** empty log message ***

src/ZEO/trigger.py

+##############################################################################
+# 
+# Zope Public License (ZPL) Version 1.0
+# -------------------------------------
+# 
+# Copyright (c) Digital Creations.  All rights reserved.
+# 
+# This license has been certified as Open Source(tm).
+# 
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+# 
+# 1. Redistributions in source code must retain the above copyright
+#    notice, this list of conditions, and the following disclaimer.
+# 
+# 2. Redistributions in binary form must reproduce the above copyright
+#    notice, this list of conditions, and the following disclaimer in
+#    the documentation and/or other materials provided with the
+#    distribution.
+# 
+# 3. Digital Creations requests that attribution be given to Zope
+#    in any manner possible. Zope includes a "Powered by Zope"
+#    button that is installed by default. While it is not a license
+#    violation to remove this button, it is requested that the
+#    attribution remain. A significant investment has been put
+#    into Zope, and this effort will continue if the Zope community
+#    continues to grow. This is one way to assure that growth.
+# 
+# 4. All advertising materials and documentation mentioning
+#    features derived from or use of this software must display
+#    the following acknowledgement:
+# 
+#      "This product includes software developed by Digital Creations
+#      for use in the Z Object Publishing Environment
+#      (http://www.zope.org/)."
+# 
+#    In the event that the product being advertised includes an
+#    intact Zope distribution (with copyright and license included)
+#    then this clause is waived.
+# 
+# 5. Names associated with Zope or Digital Creations must not be used to
+#    endorse or promote products derived from this software without
+#    prior written permission from Digital Creations.
+# 
+# 6. Modified redistributions of any form whatsoever must retain
+#    the following acknowledgment:
+# 
+#      "This product includes software developed by Digital Creations
+#      for use in the Z Object Publishing Environment
+#      (http://www.zope.org/)."
+# 
+#    Intact (re-)distributions of any official Zope release do not
+#    require an external acknowledgement.
+# 
+# 7. Modifications are encouraged but must be packaged separately as
+#    patches to official Zope releases.  Distributions that do not
+#    clearly separate the patches from the original work must be clearly
+#    labeled as unofficial distributions.  Modifications which do not
+#    carry the name Zope may be packaged in any form, as long as they
+#    conform to all of the clauses above.
+# 
+# 
+# Disclaimer
+# 
+#   THIS SOFTWARE IS PROVIDED BY DIGITAL CREATIONS ``AS IS'' AND ANY
+#   EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+#   IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+#   PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL DIGITAL CREATIONS OR ITS
+#   CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+#   SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+#   LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
+#   USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+#   ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+#   OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+#   OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+#   SUCH DAMAGE.
+# 
+# 
+# This software consists of contributions made by Digital Creations and
+# many individuals on behalf of Digital Creations.  Specific
+# attributions are listed in the accompanying credits file.
+# 
+##############################################################################
+
+# This module is a simplified version of the select_trigger module
+# from Sam Rushing's Medusa server.
+
+
+import asyncore
+#import asynchat
+
+import os
+import socket
+import string
+import thread
+    
+if os.name == 'posix':
+
+    class trigger (asyncore.file_dispatcher):
+
+        "Wake up a call to select() running in the main thread"
+
+        # This is useful in a context where you are using Medusa's I/O
+        # subsystem to deliver data, but the data is generated by another
+        # thread.  Normally, if Medusa is in the middle of a call to
+        # select(), new output data generated by another thread will have
+        # to sit until the call to select() either times out or returns.
+        # If the trigger is 'pulled' by another thread, it should immediately
+        # generate a READ event on the trigger object, which will force the
+        # select() invocation to return.
+
+        # A common use for this facility: letting Medusa manage I/O for a
+        # large number of connections; but routing each request through a
+        # thread chosen from a fixed-size thread pool.  When a thread is
+        # acquired, a transaction is performed, but output data is
+        # accumulated into buffers that will be emptied more efficiently
+        # by Medusa. [picture a server that can process database queries
+        # rapidly, but doesn't want to tie up threads waiting to send data
+        # to low-bandwidth connections]
+
+        # The other major feature provided by this class is the ability to
+        # move work back into the main thread: if you call pull_trigger()
+        # with a thunk argument, when select() wakes up and receives the
+        # event it will call your thunk from within that thread.  The main
+        # purpose of this is to remove the need to wrap thread locks around
+        # Medusa's data structures, which normally do not need them.  [To see
+        # why this is true, imagine this scenario: A thread tries to push some
+        # new data onto a channel's outgoing data queue at the same time that
+        # the main thread is trying to remove some]
+
+        def __init__ (self):
+            r, w = os.pipe()
+            self.trigger = w
+            asyncore.file_dispatcher.__init__ (self, r)
+            self.lock = thread.allocate_lock()
+            self.thunks = []
+
+        def __repr__ (self):
+            return '<select-trigger (pipe) at %x>' % id(self)
+
+        def readable (self):
+            return 1
+
+        def writable (self):
+            return 0
+
+        def handle_connect (self):
+            pass
+
+        def pull_trigger (self, thunk=None):
+            # print 'PULL_TRIGGER: ', len(self.thunks)
+            if thunk:
+                try:
+                    self.lock.acquire()
+                    self.thunks.append (thunk)
+                finally:
+                    self.lock.release()
+            os.write (self.trigger, 'x')
+
+        def handle_read (self):
+            self.recv (8192)
+            try:
+                self.lock.acquire()
+                for thunk in self.thunks:
+                    try:
+                        thunk()
+                    except:
+                        (file, fun, line), t, v, tbinfo = asyncore.compact_traceback()
+                        print 'exception in trigger thunk: (%s:%s %s)' % (t, v, tbinfo)
+                self.thunks = []
+            finally:
+                self.lock.release()
+
+else:
+
+    # win32-safe version
+
+    class trigger (asyncore.dispatcher):
+
+        address = ('127.9.9.9', 19999)
+
+        def __init__ (self):
+            a = socket.socket (socket.AF_INET, socket.SOCK_STREAM)
+            w = socket.socket (socket.AF_INET, socket.SOCK_STREAM)
+
+            # set TCP_NODELAY to true to avoid buffering
+            w.setsockopt(socket.IPPROTO_TCP, 1, 1)
+
+            # tricky: get a pair of connected sockets
+            host='127.0.0.1'
+            port=19999
+            while 1:
+                try:
+                    self.address=(host, port)
+                    a.bind(self.address)
+                    break
+                except:
+                    if port <= 19950:
+                        raise 'Bind Error', 'Cannot bind trigger!'
+                    port=port - 1
+            
+            a.listen (1)
+            w.setblocking (0)
+            try:
+                w.connect (self.address)
+            except:
+                pass
+            r, addr = a.accept()
+            a.close()
+            w.setblocking (1)
+            self.trigger = w
+
+            asyncore.dispatcher.__init__ (self, r)
+            self.lock = thread.allocate_lock()
+            self.thunks = []
+            self._trigger_connected = 0
+
+        def __repr__ (self):
+            return '<select-trigger (loopback) at %x>' % id(self)
+
+        def readable (self):
+            return 1
+
+        def writable (self):
+            return 0
+
+        def handle_connect (self):
+            pass
+
+        def pull_trigger (self, thunk=None):
+            if thunk:
+                try:
+                    self.lock.acquire()
+                    self.thunks.append (thunk)
+                finally:
+                    self.lock.release()
+            self.trigger.send ('x')
+
+        def handle_read (self):
+            self.recv (8192)
+            try:
+                self.lock.acquire()
+                for thunk in self.thunks:
+                    try:
+                        thunk()
+                    except:
+                        (file, fun, line), t, v, tbinfo = asyncore.compact_traceback()
+                        print 'exception in trigger thunk: (%s:%s %s)' % (t, v, tbinfo)
+                self.thunks = []
+            finally:
+                self.lock.release()
+
+
+
+