[svn] commit: r3324 - /branches/trac352/src/lib/python/isc/utils/serve_mixin.py
BIND 10 source code commits
bind10-changes at lists.isc.org
Fri Oct 22 15:01:24 UTC 2010
Date: Fri Oct 22 15:01:24 2010
New Revision: 3324
suggested documentation, clarifying the purpose of the mixin class and restrictions. it includes a suggested alternative of the class name.
--- branches/trac352/src/lib/python/isc/utils/serve_mixin.py (original)
+++ branches/trac352/src/lib/python/isc/utils/serve_mixin.py Fri Oct 22 15:01:24 2010
@@ -19,27 +19,51 @@
SOCK_DATA = b'somedata'
- '''Mix-In class to override the function serve_forever()
- and shutdown() in class socketserver::TCPServer.
- serve_forever() in socketserver.TCPServer use polling
- for checking request, which reduces the responsiveness to
- the shutdown request and wastes cpu at all other times.
- ServeMixIn should be used together with socketserver.TCPServer
- or some derived classes of it, and ServeMixIn must be the first
- base class in multiple inheritance, eg. MyClass(ServeMixIn,
- socketserver.TCPServer). ServeMixIn.__init__() should be called
- explicitely in derived class.
+ '''This is a mix-in class to override the function serve_forever()
+ and shutdown() in class socketserver.BaseServer.
+ As commented in the module source code, serve_forever() in
+ socketserver.BaseServer uses polling for a shutdown request, which
+ "reduces the responsiveness to a shutdown request and wastes cpu at
+ all other times."
+ This class fixes this problem by introducing internal message
+ passing via a separate socket. Note, however, that according to
+ the module documentation serve_forever() and shutdown() are not
+ categorized as functions that can be overridden via mix-ins. So
+ this mix-in class may not be compatible with future versions of
+ socketserver. It should be considered a short term workaround
+ until the original implementation is fixed.
+ The NoPollMixIn class should be used together with
+ socketserver.BaseServer or some derived classes of it, and it must
+ be placed before the corresponding socketserver class. In
+ addition, the constructor of this mix-in must be called
+ explicitely in the derived class. For example, a basic TCP server
+ without the problem of polling is created as follows:
+ class MyServer(NoPollMixIn, socketserver.TCPServer):
+ def __init__(...):
+ To shutdown the server correctly, the serve_forever() method must
+ be run in a separate thread, and shutdown() must be called from
+ some other thread.
self.__read_sock, self.__write_sock = socket.socketpair()
self.__is_shut_down = threading.Event()
def serve_forever(self, poll_interval=None):
- ''' Override the serve_forever([poll_interval]) in class
- socketserver.TCPServer. use the socketpair to wake up
- the select when shutdown() is called in anther thread.
- Note, parameter 'poll_interval' is just used to keep the
- interface, it's never used in this function.
+ ''' Overrides the serve_forever([poll_interval]) in class
+ It uses a socketpair to wake up the select when shutdown() is
+ called in anther thread. Note, parameter 'poll_interval' is
+ just used for interface compatibility; it's never used in this
# block until the self.socket or self.__read_sock is readable
@@ -61,9 +85,9 @@
'''Stops the serve_forever loop.
Blocks until the loop has finished, the function should be called
in another thread when serve_forever is running, or it will block.
self.__write_sock.send(SOCK_DATA) # make self.__read_sock readable.
self.__is_shut_down.wait() # wait until the serve thread terminate
More information about the bind10-changes