Redis7_17 高阶篇 第八章 手写Redis的分布式锁（基础版）

import redis
import uuid
import time
 
class SimpleRedLock:
    def __init__(self, connections):
        # 连接列表，应该是三个或者更多的Redis连接
        self.connections = connections
        self.retry_count = 3
        self.retry_delay = 2
        self.lock_ttl = 10
 
    def _generate_lock_key(self, resource):
        # 生成唯一的锁名
        return f"redlock:{resource}"
 
    def _acquire_lock(self, connection, lock_key, lock_value, lock_ttl):
        # 尝试在单个Redis实例上获取锁
        return connection.set(lock_key, lock_value, ex=lock_ttl, nx=True)
 
    def _release_lock(self, connection, lock_key, lock_value):
        # 释放锁的模板方法，可以根据需要进行扩展
        script = f"if redis.call('get', KEYS[1]) == ARGV[1] then return redis.call('del', KEYS[1]) else return 0 end"
        lock_key_b = bytes(lock_key, encoding='utf-8')
        lock_value_b = bytes(lock_value, encoding='utf-8')
        return connection.eval(script, 1, lock_key_b, lock_value_b)
 
    def lock(self, resource):
        # 获取锁的主函数
        lock_key = self._generate_lock_key(resource)
        lock_value = str(uuid.uuid4())
        attempts = 0
        while attempts < self.retry_count:
            for conn in self.connections:
                if self._acquire_lock(conn, lock_key, lock_value, self.lock_ttl):
                    # 如果在大多数节点上获取锁成功，则返回锁对象
                    return SimpleRedLockInstance(self, lock_key, lock_value, conn)
            time.sleep(self.retry_delay)
            attempts += 1
        return False
 
class SimpleRedLockInstance:
    def __init__(self, redlock, lock_key, lock_value, connection):
        self.redlock = redlock
        self.lock_key = lock_key
        self.lock_value = lock_value
        self.connection = connection
 
    def unlock(self):
        # 释放锁的方法
        return self.redlock._release_lock(self.connection, self.lock_key, self.lock_value)
 
# 使用示例
if __name__ == "__main__":
    # 假设有三个Redis连接
    redis_connections = [redis.Redis(host=host, port=port) for host, port in [("localhost", 6379), ("localhost", 6380), ("localhost", 6381)]]
    redlock = SimpleRedLock(redis_connections)
 
    lock_instance = redlock.lock("my_resource")
    if lock_instance:
        try:
            # 在这里执行需要锁保护的代码
            print("Acquired lock. Doing some work...")
        finally:
            # 释放锁
            lock_instance.unlock()

这个简化版本的Redis分布式锁实现了基本的锁定和解锁功能。它使用Redis SET命令的NX选项来确保只有一个客户端可以获得锁，并通过