gevent.pool – Managing greenlets in a group

The Group class in this module abstracts a group of running greenlets. When a greenlet dies, it’s automatically removed from the group. All running greenlets in a group can be waited on with Group.joinall(), or all running greenlets can be killed with Group.kill().

The Pool class, which is a subclass of Group, provides a way to limit concurrency: its spawn method blocks if the number of greenlets in the pool has already reached the limit, until there is a free slot.

class Group(*args)

Bases: gevent.pool.GroupMappingMixin

Maintain a group of greenlets that are still running.

Links to each item and removes it upon notification.

greenlet_class

alias of Greenlet

add(greenlet)

discard(greenlet)

start(greenlet)

Start the un-started greenlet and add it to the collection of greenlets this group is monitoring.

spawn(*args, **kwargs)

Begin a new greenlet with the given arguments (which are passed to the greenlet constructor) and add it to the collection of greenlets this group is monitoring.

Returns:The newly started greenlet.

join(timeout=None, raise_error=False)

kill(exception=<class 'greenlet.GreenletExit'>, block=True, timeout=None)

killone(greenlet, exception=<class 'greenlet.GreenletExit'>, block=True, timeout=None)

full()

wait_available()

class Pool(size=None, greenlet_class=None)

Bases: gevent.pool.Group

Create a new pool.

A pool is like a group, but the maximum number of members is governed by the size parameter.

Parameters:size (int) –

If given, this non-negative integer is the maximum count of active greenlets that will be allowed in this pool. A few values have special significance:

• None (the default) places no limit on the number of greenlets. This is useful when you need to track, but not limit, greenlets, as with gevent.pywsgi.WSGIServer
• 0 creates a pool that can never have any active greenlets. Attempting to spawn in this pool will block forever. This is only useful if an application uses wait_available() with a timeout and checks free_count() before attempting to spawn.

wait_available(timeout=None)

Wait until it’s possible to spawn a greenlet in this pool.

Parameters:timeout (float) – If given, only wait the specified number of seconds.

Warning

If the pool was initialized with a size of 0, this method will block forever unless a timeout is given.

Returns:A number indicating how many new greenlets can be put into the pool without blocking.

Changed in version 1.1a3: Added the timeout parameter.

full()

Return a boolean indicating whether this pool has any room for members. (True if it does, False if it doesn’t.)

free_count()

Return a number indicating approximately how many more members can be added to this pool.

add(greenlet)

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