Kryo is reset twice when used in a pool

[theigl]

Kryo 5 has a Poolable interface for objects that can be used with Pool.

When such an object is returned to the pool, Poolable.reset() is called:

/** Called when an object is freed to clear the state of the object for possible later reuse. The default implementation calls
 * {@link Poolable#reset()} if the object is {@link Poolable}. */
protected void reset (T object) {
	if (object instanceof Poolable) ((Poolable)object).reset();
}

This makes using Input und Output much easier in combination with pools.

The problem is that the Kryo class implements Poolable as well. So if autoReset is enabled (the default), Kryo.reset() will be called twice. First by auto-reset at the end of serialization, then when the object is returned to the pool.

This operation is potentially expensive, especially when references are enabled and class registration is not required.

We have two options to fix this:

1. Do not let Kryo implement Poolable
2. Document that autoReset should be disabled when Kryo is used in a pool

@magro: What do you think? We should address this before releasing 5.0 Final.

[magro]

For option 1 (Do not let Kryo implement Poolable) I'd say things would work as expected.
Probably I'm missing something - are there any drawbacks?

[theigl]

Probably I'm missing something - are there any drawbacks?

There is only one potential issue: If autoReset is disabled and Kryo is not reset manually before it is returned to the pool. Currently, the pool would ensure that the Kryo instance is always reset.

I don't have a strong opinion on this. I'm OK with either option.

[magro]

Erm, right 😉

I'd think that users turning off autoReset do this for a good reason, for them it should be ok to manually reset the Kryo instance before returning it to the pool. We should only document this so that this is clear.

So I'd prefer option 1.

[theigl]

Agreed 😉

I'll create a PR tomorrow morning.

[magro]

👍 Awesome!

[theigl]

@magro: I just pushed #758.