With Tornado’s gen module, you can turn Python generators into full-featured coroutines, but coordination among these coroutines is difficult without mutexes, semaphores, and queues. Toro provides to Tornado coroutines a set of locking primitives and queues analogous to those that Gevent provides to Greenlets, or that the standard library provides to threads.

1. Toro
Synchronization Primitives for
Tornado Coroutines

2. Vanilla Tornado
class AsyncHandler(RequestHandler):
@asynchronous
def get(self):
http_client = AsyncHTTPClient()
http_client.fetch("http://example.com",
callback=self.on_fetch)
def on_fetch(self, response):
do_something_with_response(response)
self.render("template.html")

3. tornado.gen
class GenAsyncHandler(RequestHandler):
@asynchronous
@gen.engine
def get(self):
http_client = AsyncHTTPClient()
response = yield gen.Task(
http_client.fetch, "http://example.com")
do_something_with_response(response)
self.render("template.html")

4. Great!
So where are:
• Lock
• Semaphore
• Condition
• Event
• Queue

5. Queues
A producer-consumer example

6. q = toro.JoinableQueue(maxsize=3)
@gen.engine
def producer():
for item in range(10):
print 'Sending', item
yield gen.Task(q.put, item)
@gen.engine
def consumer():
while True:
item = yield gen.Task(q.get)
print 'tt', 'Got', item
q.task_done()
producer()
consumer()
loop = ioloop.IOLoop.instance()
# block until all tasks are done
q.join(callback=loop.stop)
loop.start()

7. $ python examples/producer_consumer_example.py
Sending 0
Sending 1
Sending 2
Sending 3
! ! Got 0
! ! Got 1
! ! Got 2
! ! Got 3
Sending 4
! ! Got 4
Sending 5
! ! Got 5
Sending 6
! ! Got 6
Sending 7
! ! Got 7
Sending 8
! ! Got 8
Sending 9
! ! Got 9
$

8. toro.rtfd.org
A. Jesse Jiryu Davis
10gen
@jessejiryudavis