Jodis should return jedis resource after using it

[tobegit3hub]

Refer to official document redis/jedis#476 , jedis object is not thread-safe and we should return the resource after using it from pool.

Jedis jedis = pool.getResource();
try {
  /// ... do stuff here ... for example
  jedis.set("foo", "bar");
  String foobar = jedis.get("foo");
  jedis.zadd("sose", 0, "car"); jedis.zadd("sose", 0, "bike"); 
  Set<String> sose = jedis.zrange("sose", 0, -1);
} catch (JedisConnectionException e) {
    // returnBrokenResource when the state of the object is unrecoverable
    if (null != jedis) {
        pool.returnBrokenResource(jedis);
        jedis = null;
    }
} finally {
  /// ... it's important to return the Jedis instance to the pool once you've finished using it
  if (null != jedis)
    pool.returnResource(jedis);
}

This is the proper way to use jedis pool. I think jodis provide the interface to get resource from pool but no way to return the resource.

[ngaut]

JedisResourcePool jedisPool = new RoundRobinJedisPool("zkserver:2181", 30000, "/zk/codis/db_xxx/proxy", new JedisPoolConfig());
try (Jedis jedis = jedisPool.getResource()) {
jedis.set("foo", "bar");
String value = jedis.get("foo");
}

After the try block, jodis will rerurn it to pool automaticly

[tobegit3hub]

I have read the code and found no code about returnResource or returnBrokenResource. Refer to https://github.com/wandoulabs/codis/blob/cc90bb50d9dc6cda85c6ea0b54eb1227a41a5350/extern/jodis/src/main/java/com/wandoulabs/jodis/JedisResourcePool.java#L41, jodis ask users to close jedis instance by themselves.

However, calling jedis.close() is not good enough and doesn't help to return the resources to pool. Please refer to redis/jedis#562 and redis/jedis#500.

[c4pt0r]

https://github.com/xetorthio/jedis/blob/master/src/main/java/redis/clients/jedis/Jedis.java#L3166
shows that when closing jedis instance, it will return itself to its datasource(in our case, it's a JedisPool which created by Jodis).

jodis will not change the original behavior of JedisPool.

[tobegit3hub]

Thanks @c4pt0r . You're right and I hope you to read this through 😃

The latest version of jedis(currently 3.0.0-SNAPSHOT) has fixed this problem after redis/jedis#909. If we use 3.0.0, we can just close the jedis instances without returning resources to the pool. You can know about this from the commit message.

commit 6701b07904357dd759a11209ce98b71bd398b0fd
Refs: jedis-2.5.2-272-g6701b07
Author:     Marcos Lilljedahl <[email protected]>
AuthorDate: Mon Mar 9 02:33:50 2015 -0400
Commit:     Marcos Lilljedahl <[email protected]>
CommitDate: Mon Mar 9 02:33:50 2015 -0400

    This commit addresses the first part discussed in #909.
    To improve usability we're changing the visibility of `returnResoure`
    and `returnBrokenResource` in favor of `jedis.close()` which
    automatically returns the resource to the pool accordingly.
    As `Pool` and `Jedis` are currently in different packages i've created
    a JedisPoolAbstract class to provide a bridge between the two
    implementations

This is merged in March 9th, 2015. Before this day, all the usages without calling returnResource() or returnBrokenResource() may result in memory leak. If jodis wants to take this advantage, you should dependent on jedis:3.0.0-SNATSHOP or wait for the stable release.

You're lucky to get the right result but the current usage is totally wrong. I wanna make sure you know about that.

BTW, redis/jedis#562 has rejected to use close to recycle resources because it breaks the backward compatible. That's why they're making it 3.0.0.

[tobegit3hub]

It seems I misunderstand the commit message. The https://github.com/xetorthio/jedis/releases/tag/jedis-2.6.0 has supported TryWithResource syntax and it would be okay to use it after 2.6.0. The problem of 3.0.0 is that we can't use pool to call returnResource or returnBrokenResource. This breaks the backward compatible and we shouldn't use them after 3.0.0.

Thanks for your support @Apache9 😃

[Apache9]

My pleasure.

[jerry-024]

need not return resource？