The document discusses the use of synchronization primitives in Tornado coroutines, illustrating examples like an asynchronous HTTP fetch and producer-consumer pattern. It highlights the implementation of locks, semaphores, conditions, events, and queues, specifically using a joinable queue in a producer-consumer scenario. The examples demonstrate how to manage asynchronous tasks and control execution flow within Tornado's framework.

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