server blocks on fast method while slow method is being executed.

[Shiplu Mokaddim]

I have this server

import zerorpc

import time

class MyServer(object):

    def fast(self):

        return 'FAST'

    def slow(self):

        for i in range(5):

            time.sleep(1)

            zerorpc.gevent.sleep(0)

        return 'SLOW'

server = zerorpc.Server(MyServer(), heartbeat=None)

server.bind("tcp://0.0.0.0:9999")

try:

    zerorpc.gevent.spawn(server.run)

    while True:

        zerorpc.gevent.sleep(1)

except KeyboardInterrupt:

    print("KeyboardInterrupt Received!")

    server.close()

Now if I call slow first then fast, then fast is blocked for whole run time of slow. See this

$ zerorpc tcp://0.0.0.0:9999 slow & time zerorpc tcp://0.0.0.0:9999 fast;

[1] 31651

connecting to "tcp://0.0.0.0:9999"

connecting to "tcp://0.0.0.0:9999"

'FAST'

'SLOW'

[1]+  Done                    zerorpc tcp://0.0.0.0:9999 slow

real 0m5.072s

user 0m0.084s

sys 0m0.044s

Steps

1. slow is executed in the background

2. fast is executed wrapped with time

3. Both connect at the same time
4. fast is BLOCKED

5. fast is done

6. fast prints is result

7. slow prints its result

We can see fast executed for 5 seconds. But in slow function zerorpc.gevent.sleep(0) was executed every 1 seconds.

1. shouldn't fast return just after 1 second?

2. How can I make sure fast is not blocking while slow is being executed?

[François-Xavier Bourlet]

replace time.sleep(1) by gevent.sleep(1)

In your case, gevent.sleep(0) yields control back to the ioloop, which in turn let zerorpc run a bit, before getting back to your time.sleep(1).

zerorpc depends on gevent, and thus requires you to be cooperative.

When you call time.sleep(1) you block your thread for a second. During this time, nothing happens. Gevent ioloop is not running.

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[Shiplu Mokaddim]

By time.sleep(1) I meant a time-consuming task. In my actual code I am polling few python multiprocessing.Queue. 

It's more like:

while True:

  # check queue 1

  gevent.sleep(0)

  # check queue 2

  gevent.sleep(0)

 

But it seems, these 2 calls are not enough. I can not actually monkey patch the thread as it has issues with multiprocess.Queue. See http://www.gevent.org/gevent.monkey.html#gevent.monkey.patch_thread

In the example, I yielded only once in a loop. Correct me if I am wrong, it seems ZeroRPC executed too little which was not enough to call my `fast` function.

How can I make sure if another function is waiting to be called that will be called?

[Shiplu Mokaddim]

Seems like I found a way.

Instead of using gevent.sleep(0) I used gevent.sleep(0.1). So a bit more time for ZeroRPC to let it call my function.

0.01 works too. But it increases wait time. So I have to find a balance.