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import traceback
import eventlet
from eventlet import queue
from eventlet.support import greenlets as greenlet
import six
__all__ = ['GreenPool', 'GreenPile']
DEBUG = True
class GreenPool(object):
"""The GreenPool class is a pool of green threads.
"""
def __init__(self, size=1000):
try:
size = int(size)
except ValueError as e:
msg = 'GreenPool() expect size :: int, actual: {0} {1}'.format(type(size), str(e))
raise TypeError(msg)
if size < 0:
msg = 'GreenPool() expect size >= 0, actual: {0}'.format(repr(size))
raise ValueError(msg)
self.size = size
self.coroutines_running = set()
self.sem = eventlet.Semaphore(size)
self.no_coros_running = eventlet.Event()
def resize(self, new_size):
""" Change the max number of greenthreads doing work at any given time.
If resize is called when there are more than *new_size* greenthreads
already working on tasks, they will be allowed to complete but no new
tasks will be allowed to get launched until enough greenthreads finish
their tasks to drop the overall quantity below *new_size*. Until
then, the return value of free() will be negative.
"""
size_delta = new_size - self.size
self.sem.counter += size_delta
self.size = new_size
def running(self):
""" Returns the number of greenthreads that are currently executing
functions in the GreenPool."""
return len(self.coroutines_running)
def free(self):
""" Returns the number of greenthreads available for use.
If zero or less, the next call to :meth:`spawn` or :meth:`spawn_n` will
block the calling greenthread until a slot becomes available."""
return self.sem.counter
def spawn(self, function, *args, **kwargs):
"""Run the *function* with its arguments in its own green thread.
Returns the :class:`GreenThread <eventlet.GreenThread>`
object that is running the function, which can be used to retrieve the
results.
If the pool is currently at capacity, ``spawn`` will block until one of
the running greenthreads completes its task and frees up a slot.
This function is reentrant; *function* can call ``spawn`` on the same
pool without risk of deadlocking the whole thing.
"""
# if reentering an empty pool, don't try to wait on a coroutine freeing
# itself -- instead, just execute in the current coroutine
current = eventlet.getcurrent()
if self.sem.locked() and current in self.coroutines_running:
# a bit hacky to use the GT without switching to it
gt = eventlet.greenthread.GreenThread(current)
gt.main(function, args, kwargs)
return gt
else:
self.sem.acquire()
gt = eventlet.spawn(function, *args, **kwargs)
if not self.coroutines_running:
self.no_coros_running = eventlet.Event()
self.coroutines_running.add(gt)
gt.link(self._spawn_done)
return gt
def _spawn_n_impl(self, func, args, kwargs, coro):
try:
try:
func(*args, **kwargs)
except (KeyboardInterrupt, SystemExit, greenlet.GreenletExit):
raise
except:
if DEBUG:
traceback.print_exc()
finally:
if coro is None:
return
else:
coro = eventlet.getcurrent()
self._spawn_done(coro)
def spawn_n(self, function, *args, **kwargs):
"""Create a greenthread to run the *function*, the same as
:meth:`spawn`. The difference is that :meth:`spawn_n` returns
None; the results of *function* are not retrievable.
"""
# if reentering an empty pool, don't try to wait on a coroutine freeing
# itself -- instead, just execute in the current coroutine
current = eventlet.getcurrent()
if self.sem.locked() and current in self.coroutines_running:
self._spawn_n_impl(function, args, kwargs, None)
else:
self.sem.acquire()
g = eventlet.spawn_n(
self._spawn_n_impl,
function, args, kwargs, True)
if not self.coroutines_running:
self.no_coros_running = eventlet.Event()
self.coroutines_running.add(g)
def waitall(self):
"""Waits until all greenthreads in the pool are finished working."""
assert eventlet.getcurrent() not in self.coroutines_running, \
"Calling waitall() from within one of the " \
"GreenPool's greenthreads will never terminate."
if self.running():
self.no_coros_running.wait()
def _spawn_done(self, coro):
self.sem.release()
if coro is not None:
self.coroutines_running.remove(coro)
# if done processing (no more work is waiting for processing),
# we can finish off any waitall() calls that might be pending
if self.sem.balance == self.size:
self.no_coros_running.send(None)
def waiting(self):
"""Return the number of greenthreads waiting to spawn.
"""
if self.sem.balance < 0:
return -self.sem.balance
else:
return 0
def _do_map(self, func, it, gi):
for args in it:
gi.spawn(func, *args)
gi.done_spawning()
def starmap(self, function, iterable):
"""This is the same as :func:`itertools.starmap`, except that *func* is
executed in a separate green thread for each item, with the concurrency
limited by the pool's size. In operation, starmap consumes a constant
amount of memory, proportional to the size of the pool, and is thus
suited for iterating over extremely long input lists.
"""
if function is None:
function = lambda *a: a
# We use a whole separate greenthread so its spawn() calls can block
# without blocking OUR caller. On the other hand, we must assume that
# our caller will immediately start trying to iterate over whatever we
# return. If that were a GreenPile, our caller would always see an
# empty sequence because the hub hasn't even entered _do_map() yet --
# _do_map() hasn't had a chance to spawn a single greenthread on this
# GreenPool! A GreenMap is safe to use with different producer and
# consumer greenthreads, because it doesn't raise StopIteration until
# the producer has explicitly called done_spawning().
gi = GreenMap(self.size)
eventlet.spawn_n(self._do_map, function, iterable, gi)
return gi
def imap(self, function, *iterables):
"""This is the same as :func:`itertools.imap`, and has the same
concurrency and memory behavior as :meth:`starmap`.
It's quite convenient for, e.g., farming out jobs from a file::
def worker(line):
return do_something(line)
pool = GreenPool()
for result in pool.imap(worker, open("filename", 'r')):
print(result)
"""
return self.starmap(function, six.moves.zip(*iterables))
class GreenPile(object):
"""GreenPile is an abstraction representing a bunch of I/O-related tasks.
Construct a GreenPile with an existing GreenPool object. The GreenPile will
then use that pool's concurrency as it processes its jobs. There can be
many GreenPiles associated with a single GreenPool.
A GreenPile can also be constructed standalone, not associated with any
GreenPool. To do this, construct it with an integer size parameter instead
of a GreenPool.
It is not advisable to iterate over a GreenPile in a different greenthread
than the one which is calling spawn. The iterator will exit early in that
situation.
"""
def __init__(self, size_or_pool=1000):
if isinstance(size_or_pool, GreenPool):
self.pool = size_or_pool
else:
self.pool = GreenPool(size_or_pool)
self.waiters = queue.LightQueue()
self.counter = 0
def spawn(self, func, *args, **kw):
"""Runs *func* in its own green thread, with the result available by
iterating over the GreenPile object."""
self.counter += 1
try:
gt = self.pool.spawn(func, *args, **kw)
self.waiters.put(gt)
except:
self.counter -= 1
raise
def __iter__(self):
return self
def next(self):
"""Wait for the next result, suspending the current greenthread until it
is available. Raises StopIteration when there are no more results."""
if self.counter == 0:
raise StopIteration()
return self._next()
__next__ = next
def _next(self):
try:
return self.waiters.get().wait()
finally:
self.counter -= 1
# this is identical to GreenPile but it blocks on spawn if the results
# aren't consumed, and it doesn't generate its own StopIteration exception,
# instead relying on the spawning process to send one in when it's done
class GreenMap(GreenPile):
def __init__(self, size_or_pool):
super(GreenMap, self).__init__(size_or_pool)
self.waiters = queue.LightQueue(maxsize=self.pool.size)
def done_spawning(self):
self.spawn(lambda: StopIteration())
def next(self):
val = self._next()
if isinstance(val, StopIteration):
raise val
else:
return val
__next__ = next