Documented the new error_callback keyword argument to multiprocessing.Pool's apply_async and map_async
diff --git a/Doc/library/multiprocessing.rst b/Doc/library/multiprocessing.rst
index 3908bcb..4f3f1cd 100644
--- a/Doc/library/multiprocessing.rst
+++ b/Doc/library/multiprocessing.rst
@@ -1582,14 +1582,21 @@
suited for performing work in parallel. Additionally, the passed in
function is only executed in one of the workers of the pool.
- .. method:: apply_async(func[, args[, kwds[, callback]]])
+ .. method:: apply_async(func[, args[, kwds[, callback[, error_callback]]]])
A variant of the :meth:`apply` method which returns a result object.
If *callback* is specified then it should be a callable which accepts a
single argument. When the result becomes ready *callback* is applied to
- it (unless the call failed). *callback* should complete immediately since
- otherwise the thread which handles the results will get blocked.
+ it, that is unless the call failed, in which case the *error_callback*
+ is applied instead
+
+ If *error_callback* is specified then it should be a callable which
+ accepts a single argument. If the target function fails, then
+ the *error_callback* is called with the exception instance.
+
+ Callbacks should complete immediately since otherwise the thread which
+ handles the results will get blocked.
.. method:: map(func, iterable[, chunksize])
@@ -1606,8 +1613,15 @@
If *callback* is specified then it should be a callable which accepts a
single argument. When the result becomes ready *callback* is applied to
- it (unless the call failed). *callback* should complete immediately since
- otherwise the thread which handles the results will get blocked.
+ it, that is unless the call failed, in which case the *error_callback*
+ is applied instead
+
+ If *error_callback* is specified then it should be a callable which
+ accepts a single argument. If the target function fails, then
+ the *error_callback* is called with the exception instance.
+
+ Callbacks should complete immediately since otherwise the thread which
+ handles the results will get blocked.
.. method:: imap(func, iterable[, chunksize])