socket recv returning multiple data types

[jerzyk]

python 3.4 - when using green sockets, most of the time socket.recv is returning bytes, but when
communication is broken, it returns string

sock = eventlet.connect((SERVER_ADDRESS, port))

while True:
    _d = sock.recv(1024)
    print('recv: %s %s' % (_d, type(_d)))

returns:

Starting processes..
Connecting to port 9800
Connecting to port 9800
recv: b'{Ping}\r' <class 'bytes'>
record (port: 9800): b'{Ping}'
recv: b'{Ping}\r' <class 'bytes'>
record (port: 9800): b'{Ping}'
recv: b'' <class 'bytes'>
recv:  <class 'str'>

[temoto]

I tried the following code to reproduce your issue and it consistently returns bytes. What kind of "communication is broken" exactly are you experiencing?

def test_recv_types():
    server_sock = eventlet.listen(('127.0.0.1', 0))

    def server():
        conn, _ = server_sock.accept()
        conn.send(b'a')
        eventlet.sleep(0.1)
        conn.close()
    server_thread = eventlet.spawn(server)

    client = eventlet.connect(server_sock.getsockname())
    s1 = client.recv(1024)
    assert type(s1) == type(b'')
    # tried few combinations of server and client failures
    # server_thread.kill()
    # client.shutdown(socket.SHUT_RDWR)
    # client.close()
    s2 = client.recv(1)
    assert type(s2) == type(b'')

[jerzyk]

as you see, in the second part of the ticket, recv returns empty string after server closed a socket.
my example code is from a client

[temoto]

Can you run the code I pasted? It does exactly that: server closes connection after 0.1s timeout, then s2 is empty b''. What version of eventlet do you use?

[jerzyk]

eventlet 0.17.4, did not get errors on your code, here is mine (I was trying to put it into one file, but then there were no errors...)

run server, then client, stop server, assertion error shows

server:

#!/usr/bin/env python
import eventlet


def server():
    server_sock = eventlet.listen(('127.0.0.1', 9801))
    conn, _ = server_sock.accept()
    while True:
        conn.sendall(b'{Ping}')
        eventlet.sleep(2)
    conn.close()


if __name__ == "__main__":
    server_thread = eventlet.spawn(server)
    server_thread.wait()

client:

#!/usr/bin/env python
import eventlet


def handler():
    socket = eventlet.connect(('127.0.0.1', 9801))
    data = b''
    while True:
        timeout = eventlet.Timeout(5)
        try:
            data = socket.recv(1024)
            assert isinstance(data, bytes)
        except eventlet.Timeout:
            socket.sendall(b'pong')
        finally:
            timeout.cancel()

        if not data:
            eventlet.sleep(2)
            socket.sendall(b'ping')

    socket.close()


if __name__ == "__main__":
    pool = eventlet.GreenPool(2)
    pool.spawn_n(handler)
    pool.waitall()

[temoto]

Thank you. Indeed, it deceptively passes when client and server are just two green threads.

Error was in eventlet/green/base.py:318: return ''.

[jerzyk]

@temoto what's an oldest supported python version?(I could not find it in the docs) - with 2.5 supported there should be six.b('')

[temoto]

That's not a problem, we use few 2.6+ syntax features already. Fix is merged in master 001f31f.