consumer_producer

consumer_producer.py

# Example 1
from tornado import gen, queues
from tornado.ioloop import IOLoop

@gen.coroutine
def consumer(queue, num_expected):
    for _ in range(num_expected):
        # heavy I/O or network task
        print('got: %s' % (yield queue.get()))


@gen.coroutine
def producer(queue, num_items):
    for i in range(num_items):
        print('putting %s' % i)
        yield queue.put(i)

@gen.coroutine
def main():
    """
    Starts producer and consumer and wait till they finish
    """
    yield [producer(q, producer_num_items), consumer(q, producer_num_items)]

queue_size = 1
producer_num_items = 5
q = queues.Queue(queue_size)

results = IOLoop.current().run_sync(main)


# Output:
# putting 0
# putting 1
# got: 0
# got: 1
# putting 2
# putting 3
# putting 4
# got: 2
# got: 3
# got: 4


# Example 2
# Condition
# A condition allows one or more coroutines to wait until notified.
from tornado import gen
from tornado.ioloop import IOLoop
from tornado.locks import Condition

my_condition = Condition()

@gen.coroutine
def waiter():
    print("I'll wait right here")
    yield my_condition.wait()
    print("Received notification now doing my things")

@gen.coroutine
def notifier():
    yield gen.sleep(60)
    print("About to notify")
    my_condition.notify()
    print("Done notifying")

@gen.coroutine
def runner():
    # Wait for waiter() and notifier() in parallel
    yield([waiter(), notifier()])

results = IOLoop.current().run_sync(runner)


# output:

# I'll wait right here
# About to notify
# Done notifying
# Received notification now doing my things