Fix memory leak for batch delete

[SophieGuo410]

Summary

Fix memory leak for batch delete

Testing Done

unit test

[djycheng]

Why are we only seeing this issue now? Were we relying on the garbage collector? Is there increased load in batch delete requests that prevents the garbage collector from keeping up?

[SophieGuo410]

this is direct memory leak. so no gc, we have to release them.
we only see bunch of these when we enable the paranoid mode and the direct memory usage goes up to 20G.
we will keep investigate other leaks

[satishkotha]

does consumeContentAsBuf increase ref count? is that why release is being done here? is channel.close() getting called correctly?

[satishkotha]

it looks like consumeContentAsByteBuf transfers ownership. can we refactor that method to be safe? something like:

public byte[] consumeContentAsBytes() {
ByteBuf buf = null;
try {
buf = // consumeContentAsByteBuf() code
byte[] data = new byte[buf.readableBytes()];
buf.readBytes(data);
return data;
} finally {
if (buf != null) { buf.release() };
}
}

[SophieGuo410]

done