ZeroMQ配合gevent實現高併發

原文鏈接：https://dustinoprea.com/2014/04/23/using-zeromq-with-coroutines-gevent-under-python/

ZeroMQ (0MQ) [官方文檔]是一個漂亮的庫，它用一個非常輕便的基於模式的包裝器，替換socket層。
另外，0MQ通常還保證一次讀取將返回一條消息(或多部分消息的一部分)。

gevent是一個基於協程的第三方網絡庫，它允許你當發生IO阻塞時(如網絡請求)去執行其他的操作，當你並行執行很多IO耗時的操作時能達到非常好的併發效果。

gevent是一種折衷方案，可以以同步的操作效率提高到與多線程相當的程度，典型的應用場景就是請求網絡的操作。

曾經有一段時間ZeroMQ不支持這一點(必須使用一個名爲gevent zmq的包)，但後來zmq與gevent兼容了。最新的版本18.1.0是支持的。

爲了實現協程併發效果，需要引用import zmq.green 而不是 import zmq。

服務端示例代碼：

import gevent
import time
import zmq.green as zmq

_BINDING = 'tcp://127.0.0.1:7000'
context = zmq.Context()

def server():
    server_socket = context.socket(zmq.REP)
    server_socket.bind(_BINDING)

    while True:
        received = server_socket.recv()
        print("Received: [{}]\n".format(received))
        server_socket.send_string('TestResponse')

server = gevent.spawn(server)
server.join()

對應的客戶端

import gevent
import time
import zmq.green as zmq

_BINDING = 'tcp://127.0.0.1:7000'
context = zmq.Context()

def client():
    client_socket = context.socket(zmq.REQ)
    client_socket.connect(_BINDING)
    client_socket.send_string("TestMessage")
    response = client_socket.recv()
    print("Response: [{}] at {}".format(response, time.time()))

server = gevent.spawn(server)
clients = [gevent.spawn(client) for i in range(1000)]

分別啓動服務端和客戶端，服務端輸出：

Received: [b'TestMessage']

Received: [b'TestMessage']

Received: [b'TestMessage']
.....

客戶端輸出：

Response: [b'TestResponse'] at 1565866988.859491
Response: [b'TestResponse'] at 1565866988.859531
Response: [b'TestResponse'] at 1565866988.859568
Response: [b'TestResponse'] at 1565866988.859606
Response: [b'TestResponse'] at 1565866988.859644
Response: [b'TestResponse'] at 1565866988.859683
Response: [b'TestResponse'] at 1565866988.859721
Response: [b'TestResponse'] at 1565866988.860918
Response: [b'TestResponse'] at 1565866988.8609679
Response: [b'TestResponse'] at 1565866988.861006
......

參考文檔：
Using ZeroMQ With Coroutines (gevent) Under Python