通过实例解析Python RPC实现原理及方法

时间：2021-05-24 08:51:04|栏目：Python代码|点击：次

单线程同步

使用socket传输数据
使用json序列化消息体
struct将消息编码为二进制字节串，进行网络传输

消息协议

// 输入
{
  in: "ping",
  params: "ireader 0"
}

// 输出
{
  out: "pong",
  result: "ireader 0"
}

客户端 client.py

# coding: utf-8
# client.py

import json
import time
import struct
import socket


def rpc(sock, in_, params):
  response = json.dumps({"in": in_, "params": params}) # 请求消息体
  length_prefix = struct.pack("I", len(response)) # 请求长度前缀
  sock.sendall(length_prefix)
  sock.sendall(response)
  length_prefix = sock.recv(4) # 响应长度前缀
  length, = struct.unpack("I", length_prefix)
  body = sock.recv(length) # 响应消息体
  response = json.loads(body)
  return response["out"], response["result"] # 返回响应类型和结果

if __name__ == '__main__':
  s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
  s.connect(("localhost", 8080))
  for i in range(10): # 连续发送10个rpc请求
    out, result = rpc(s, "ping", "ireader %d" % i)
    print out, result
    time.sleep(1) # 休眠1s，便于观察
  s.close() # 关闭连接

服务端 blocking_single.py

# coding: utf8
# blocking_single.py

import json
import struct
import socket


def handle_conn(conn, addr, handlers):
  print addr, "comes"
  while True: # 循环读写
    length_prefix = conn.recv(4) # 请求长度前缀
    if not length_prefix: # 连接关闭了
      print addr, "bye"
      conn.close()
      break # 退出循环，处理下一个连接
    length, = struct.unpack("I", length_prefix)
    body = conn.recv(length) # 请求消息体
    request = json.loads(body)
    in_ = request['in']
    params = request['params']
    print in_, params
    handler = handlers[in_] # 查找请求处理器
    handler(conn, params) # 处理请求


def loop(sock, handlers):
  while True:
    conn, addr = sock.accept() # 接收连接
    handle_conn(conn, addr, handlers) # 处理连接


def ping(conn, params):
  send_result(conn, "pong", params)


def send_result(conn, out, result):
  response = json.dumps({"out": out, "result": result}) # 响应消息体
  length_prefix = struct.pack("I", len(response)) # 响应长度前缀
  conn.sendall(length_prefix)
  conn.sendall(response)


if __name__ == '__main__':
  sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM) # 创建一个TCP套接字
  sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1) # 打开reuse addr选项
  sock.bind(("localhost", 8080)) # 绑定端口
  sock.listen(1) # 监听客户端连接
  handlers = { # 注册请求处理器
    "ping": ping
  }
  loop(sock, handlers) # 进入服务循环