feat: add redis-distributed-lock.md

利用 Redis String 实现分布式锁

Author: yanglbme

README.md

@@ -39,11 +39,13 @@ Redis 基础的数据结构有 5 种，分别是：
 每一种数据结构都有它对应的实践场景，下面几个小节会就这几种数据结构展开讨论，也欢迎各位开发朋友来分享更多的应用案例。
 
 ### 字符串
+- [说说分布式锁的实现方式？](/docs/redis-distributed-lock.md)
 
 ### 列表
 - 如何利用 Redis List 实现异步消息队列？
 
 ### 哈希
+- [登录会话，用 Redis 该怎么做？](/docs/redis-hash-session-token.md)
 
 ### 集合
 

docs/redis-distributed-lock.md

@@ -0,0 +1,105 @@
+# 使用 Redis String 实现分布式锁
+
+
+## 代码实现
+1. Python 版本
+
+```python
+import random
+import string
+import time
+
+from redis import Redis
+
+
+def generate_random_value():
+    return ''.join(random.sample(string.ascii_letters + string.digits, 32))
+
+
+# 设定默认过期时长为 10s
+DEFAULT_TIMEOUT = 10
+
+
+class DistributedLock:
+    def __init__(self, client: Redis, key: str):
+        self.client = client
+        self.key = key
+
+    def acquire(self, timeout=DEFAULT_TIMEOUT) -> bool:
+        """尝试获取锁"""
+        res = self.client.set(self.key, generate_random_value(), ex=timeout, nx=True)  # ex 表示过期时长秒数，nx 表示 key 不存在时才设置
+        return res is True
+
+    def release(self) -> bool:
+        """尝试释放锁"""
+        return self.client.delete(self.key) == 1
+
+
+if __name__ == '__main__':
+    redis = Redis(decode_responses=True)
+    lock = DistributedLock(redis, 'bingo_distributed_lock')
+
+    print(lock.acquire(10))  # True
+    print(lock.acquire(10))  # False
+
+    time.sleep(10)
+    print(lock.acquire())  # True
+    print(lock.release())  # True
+
+    print(lock.acquire())  # True
+```
+
+2. Java 版本
+
+```java
+import redis.clients.jedis.Jedis;
+import redis.clients.jedis.params.SetParams;
+
+import java.util.UUID;
+import java.util.concurrent.TimeUnit;
+
+
+public class DistributedLock {
+
+    private Jedis client;
+    private String key;
+
+    public DistributedLock(Jedis client, String key) {
+        this.client = client;
+        this.key = key;
+    }
+
+    private String generateRandomValue() {
+        return UUID.randomUUID().toString().replaceAll("-", "");
+    }
+
+
+    public boolean acquire(int timeout) {
+        SetParams params = new SetParams().ex(timeout).nx();
+        return client.set(key, generateRandomValue(), params) != null;
+    }
+
+    public boolean acquire() {
+        int timeout = 10;
+        return acquire(timeout);
+    }
+
+    public boolean release() {
+        return client.del(key) == 1;
+    }
+
+    public static void main(String[] args) throws InterruptedException {
+        Jedis jedis = new Jedis();
+        DistributedLock lock = new DistributedLock(jedis, "bingo_distributed_lock");
+
+        System.out.println(lock.acquire(10)); // true
+        System.out.println(lock.acquire(10)); // false
+
+        TimeUnit.SECONDS.sleep(10);
+        System.out.println(lock.acquire()); // true
+        System.out.println(lock.release()); // true
+
+        System.out.println(lock.acquire()); // true
+    }
+}
+```