Zeromq zmq.Poller & stdin

Question

Can I use zmq.Pollerstdin to query data availability? If not, would it be most efficient to wait for a poll, at some time (ideally), for data availability for zeromq and stdin sockets?

Answer 1

yes, zmq pollers support native FDs, including stdin, etc., so you just need to check sys.stdin.fileno():

poller = zmq.Poller()
poller.register(sys.stdin, zmq.POLLIN)
poller.register(mysocket, zmq.POLLIN)
evts = dict(poller.poll(1000))
stdin_ready = evts.get(sys.stdin.fileno(), False)
socket_ready = evts.get(mysocket, False)

Answer 2

If you are sure that you will never run on Windows, you can simply register sys.stdinwith zmq.Poller(as described by minrk, above ).

select() Winsock "" , , Windows 0MQ inproc.

:

def forward_lines(stream, socket):
    """Read lines from `stream` and send them over `socket`."""
    try:
        line = stream.readline()
        while line:
            socket.send(line[:-1])
            line = stream.readline()
        socket.send('')  # send "eof message".
    finally:
        # NOTE: `zmq.Context.term()` in the main thread will block until this
        #       socket is closed, so we can't run this function in daemon
        #       thread hoping that it will just close itself.
        socket.close()


def forward_standard_input(context):
    """Start a thread that will bridge the standard input to a 0MQ socket and
    return an exclusive pair socket from which you can read lines retrieved
    from the standard input.  You will receive a final empty line when the EOF
    character is input to the keyboard."""
    reader = context.socket(zmq.PAIR)
    reader.connect('inproc://standard-input')
    writer = context.socket(zmq.PAIR)
    writer.bind('inproc://standard-input')
    thread = threading.Thread(target=forward_lines,
                              args=(sys.stdin, writer))
    thread.start()
    return reader


if __name__ == '__main__':
    context = zmq.Context()
    reader = forward_standard_input(context)
    poller = zmq.Poller()
    poller.register(reader, zmq.POLLIN)
    poller.register(...)

    events = dict(poller.poll())
    if events.get(reader, 0) & zmq.POLLIN:
        line = reader.recv()
        # process line.
    if events.get(..., 0) & zmq.POLLIN:
        # ...