关于python：Pyzmq高水位标记在发布套接字上不起作用


Pyzmq high-water mark not working on pub socket

根据ZeroMQ文档，一旦排队的消息数达到最高水位，发布套接字应该丢弃消息。

在以下示例中，这似乎不起作用(是的，在绑定/连接之前，我确实设置了hwm)：

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import time
import pickle
from threading import Thread
import zmq

ctx = zmq.Context()

def pub_thread():
    pub = ctx.socket(zmq.PUB)
    pub.set_hwm(2)
    pub.bind('tcp://*:5555')

    i = 0
    while True:
        # Send message every 100ms
        time.sleep(0.1)
        pub.send_string("test", zmq.SNDMORE)
        pub.send_pyobj(i)
        i += 1

def sub_thread():
    sub = ctx.socket(zmq.SUB)
    sub.subscribe("test")
    sub.connect('tcp://localhost:5555')
    while True:
        # Receive messages only every second
        time.sleep(1)
        msg = sub.recv_multipart()
        print("Sub: %d" % pickle.loads(msg[1]))

t_pub = Thread(target=pub_thread)
t_sub = Thread(target=sub_thread)
t_pub.start()
t_sub.start()

while True:
    pass

我在pub上发送消息的速度比在子套接字上读取消息的速度快10倍，hwm设置为2。我希望只能收到大约每10条消息。 相反，我看到以下输出：

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Sub: 0
Sub: 1
Sub: 2
Sub: 3
Sub: 4
Sub: 5
Sub: 6
Sub: 7
Sub: 8
Sub: 9
Sub: 10
Sub: 11
Sub: 12
Sub: 13
Sub: 14
...

所以我看到所有消息都到达了，因此它们一直排在队列中，直到我阅读它们为止。 在连接之前在子插座上添加hwm = 2时也是如此。

我在做什么错还是误解了hwm？

我使用pyzmq版本17.1.2

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通过借用我在Github中打开的问题的答案，我对答案进行了如下更新：

Messages are held in operating system's network buffers. I have found
HWMs to be not that useful because of that. Here is modified code
where subscriber misses messages:

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import time
import pickle
import zmq
from threading import Thread
import os

ctx = zmq.Context()

def pub_thread():
    pub = ctx.socket(zmq.PUB)
    pub.setsockopt(zmq.SNDHWM, 2)
    pub.setsockopt(zmq.SNDBUF, 2*1024)  # See: http://api.zeromq.org/4-2:zmq-setsockopt
    pub.bind('tcp://*:5555')
    i = 0
    while True:
        time.sleep(0.001)
        pub.send_string(str(i), zmq.SNDMORE)
        pub.send(os.urandom(1024))
        i += 1

def sub_thread():
    sub = ctx.socket(zmq.SUB)
    sub.setsockopt(zmq.SUBSCRIBE, b'')
    sub.setsockopt(zmq.RCVHWM, 2)
    sub.setsockopt(zmq.RCVBUF, 2*1024)
    sub.connect('tcp://localhost:5555')
    while True:
        time.sleep(0.1)
        msg, _ = sub.recv_multipart()
        print("Received:", msg.decode())

t_pub = Thread(target=pub_thread)
t_pub.start()
sub_thread()

Output looks something like this:

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Received: 0
Received: 1
Received: 2
Received: 3
Received: 4
Received: 5
Received: 6
Received: 47
Received: 48
Received: 64
Received: 65
Received: 84
Received: 85
Received: 159
Received: 160
Received: 270

Messages are missed because all queues/buffers are full and publisher
starts to drop messages (see documentation for ZMQ_PUB:
http://api.zeromq.org/4-2:zmq-socket).

[注意]：

  • 您应该在侦听器/订阅者和广告商/发布者中使用高水印选项。
  • 这些职位也相关(职位1-职位2)
  • sock.setsockopt(zmq.CONFLATE, 1)是仅获取在订户方定义的最后一条消息的另一个选项。
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