Python ZeroMQ 推/拉——丢失消息? [英] Python ZeroMQ PUSH/PULL -- Lost Messages?

问题描述

我正在尝试在 PUSH/PULL 模式下使用 python 和 zeroMQ，发送大小为 4[MB]<的消息/strong> 每隔几秒.

I am trying to use python with zeroMQ in PUSH / PULL mode, sending messages of size 4[MB] every few seconds.

出于某种原因，虽然看起来所有消息都已发送，但服务器似乎只收到了其中的一些.我在这里缺少什么?

For some reason, while it looks like all the messages are sent, ONLY SOME of them appear to have been received by the server. What am I missing here?

这是客户端的代码——client.py

import zmq
import struct

# define a string of size 4[MB] 
msgToSend = struct.pack('i', 45) * 1000 * 1000 

context = zmq.Context()
socket = context.socket(zmq.PUSH)
socket.connect("tcp://127.0.0.1:5000")

# print the message size in bytes
print len(msgToSend)

socket.send(msgToSend)

print "Sent message"

这里是服务器的代码——server.py

And here is the code for the server -- server.py

import zmq
import struct

context = zmq.Context()
socket = context.socket(zmq.PULL)
socket.bind("tcp://127.0.0.1:5000")

while True:
    # receive the message
    msg = socket.recv()

    print "Message Size is: {0} [MB]".format( len(msg) / (1000 * 1000) )

我错过了什么?如何保证消息始终发送且不丢失?

What am I missing? How do I guarantee that messages are always sent and not lost?

以防万一，我使用的是 Ubuntu 10.04 32 位 Core Duo 机器，内存为 2[GB].

In case it matters, I am using Ubuntu 10.04 32bit, Core Duo machine with 2[GB] RAM.

注意:我使用 RabbitMQ 尝试了相同的示例，一切正常——没有消息丢失.我很困惑，因为我经常听到对 zeroMQ 的赞美.为什么在 RabbitMQ 成功的地方失败了?

NOTE: I tried the same example using RabbitMQ and everything works well -- no message is lost. I am perplexed as I often hear praises of zeroMQ. Why did it fail where RabbitMQ succeed?

推荐答案

问题在于，当程序退出时，套接字会立即关闭并以 0 的有效 LINGER 进行垃圾收集(即它会将所有未发送的消息扔掉).对于较大的消息，这是一个问题，因为它们的发送时间比套接字被垃圾收集所需的时间长.

The problem is that when the program exits, the socket gets closed immediately and garbage collected with an effective LINGER of 0 (i.e. it throws any unsent messages away). This is a problem for larger messages because they take longer to send than it takes for the socket to be garbage collected.

您可以通过在程序退出之前放置一个 sleep(0.1) 来避免这种情况(延迟套接字和上下文被垃圾收集).

You can avoid this by putting a sleep(0.1) just before the program exits (to delay the socket and context being garbage collected).

socket.setsockopt(zmq.LINGER, -1)(这是默认值)应该可以避免这个问题，但由于某种原因我没有时间调查它并没有.

socket.setsockopt(zmq.LINGER, -1) (which is the default) should avoid this problem, but it doesn't for some reason that I haven't had time to investigate.

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