Merged revisions 77794 via svnmerge from

svn+ssh://pythondev@svn.python.org/python/trunk

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  r77794 | jesse.noller | 2010-01-26 22:05:57 -0500 (Tue, 26 Jan 2010) | 1 line

  Issue #6963: Added maxtasksperchild argument to multiprocessing.Pool
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1 files changed, 16 insertions, 1 deletions

diff --git a/Doc/library/multiprocessing.rst b/Doc/library/multiprocessing.rst
index a2cdb02..6d7e768 100644
--- a/Doc/library/multiprocessing.rst
+++ b/Doc/library/multiprocessing.rst
@@ -1535,7 +1535,7 @@ Process Pools
 One can create a pool of processes which will carry out tasks submitted to it
 with the :class:`Pool` class.
 
-.. class:: multiprocessing.Pool([processes[, initializer[, initargs]]])
+.. class:: multiprocessing.Pool([processes[, initializer[, initargs[, maxtasksperchild]]]])
 
    A process pool object which controls a pool of worker processes to which jobs
    can be submitted.  It supports asynchronous results with timeouts and
@@ -1546,6 +1546,21 @@ with the :class:`Pool` class.
    *initializer* is not ``None`` then each worker process will call
    ``initializer(*initargs)`` when it starts.
 
+   *maxtasksperchild* is the number of tasks a worker process can complete
+   before it will exit and be replaced with a fresh worker process, to enable
+   unused resources to be freed. The default *maxtasksperchild* is None, which
+   means worker processes will live as long as the pool.
+
+   .. note::
+
+        Worker processes within a :class:`Pool` typically live for the complete
+        duration of the Pool's work queue. A frequent pattern found in other
+        systems (such as Apache, mod_wsgi, etc) to free resources held by
+        workers is to allow a worker within a pool to complete only a set
+        amount of work before being exiting, being cleaned up and a new
+        process spawned to replace the old one. The *maxtasksperchild*
+        argument to the :class:`Pool` exposes this ability to the end user.
+
    .. method:: apply(func[, args[, kwds]])
 
       Call *func* with arguments *args* and keyword arguments *kwds*.  It blocks