如何在多线程环境中使用JedisPool创建多个Jedis实例

Question

I tried to use JedisPool to create several Jedis instances for multithreading usage (each thread can have one Jedis instance). But when I tried to create multiple instances by using JedisPool.getResource(), it always gives me the same Jedis instance. And the following code will also give me redis.clients.jedis.exceptions.JedisConnectionException: Unexpected end of stream because of single Jedis instance for multiple threads.

private final static JedisPoolConfig poolConfig = buildPoolConfig();
private static JedisPool jedisPool = new JedisPool(poolConfig, "localhost");

public static void main(String[] args) throws Exception {
    MyThread[] myThreads = new MyThread[4];
    for (int i = 0; i < myThreads.length; i++) {
       try (Jedis jedis = jedisPool.getResource()) {
           System.out.println("jedis " + i  + ": "+ jedis);
           myThreads[i] = new MyThread(jedis);
           myThreads[i].start();
       }
    }
    jedisPool.close();
}

private static JedisPoolConfig buildPoolConfig() {
    final JedisPoolConfig poolConfig = new JedisPoolConfig();
    poolConfig.setMaxTotal(128);
    poolConfig.setMaxIdle(128);
    poolConfig.setMinIdle(16);
    poolConfig.setTestOnBorrow(true);
    poolConfig.setTestOnReturn(true);
    poolConfig.setTestWhileIdle(true);
    poolConfig.setMinEvictableIdleTimeMillis(Duration.ofSeconds(60).toMillis());
    poolConfig.setTimeBetweenEvictionRunsMillis(Duration.ofSeconds(30).toMillis());
    poolConfig.setNumTestsPerEvictionRun(3);
    poolConfig.setBlockWhenExhausted(true);
    return poolConfig;
}

Any help would be really appreciated. Thanks!

Answer 1

You are supposed to use JedisPool in a multi-threaded environment. But, by your implementation, you are actually using Jedis in that situation.

To resolve that you can take JedisPool instead of Jedis for MyThread constructor.

public static void main(String[] args) throws Exception {
    MyThread[] myThreads = new MyThread[4];
    for (int i = 0; i < myThreads.length; i++) {
        myThreads[i] = new MyThread(jedisPool);
        myThreads[i].start();
    }
    jedisPool.close();
}

During every operation in MyThread class, take a Jedis object from pool and use it. For example:

class MyThread {
    void doSomething() {
        try (Jedis jedis = jedisPool.getResource()) {
            jedis.exists(key);
        }
    }
}