Config option to allow config netty event loop threads

[zhenlineo]

Added configuration option to allow users to config how many netty event loop threads they want to use.

[PetrJanouch]

Nice!

[elR1co]

Hello. Thanks a lot for the work done.
I am currently using version 1.7.5. In my application, I need to use a separate pool for a service, in order to restrict the number of connections, only for this case. In this case, I have two separate Driver instances, one for my generic pool, and one for this specific service. I noticed that every time I create a Driver instance, there are 2 * CPUs Neo4jDriverIO threads which are created, and in my case where I would just need maybe 5 connections max, I would not need more than 2 threads for example.
My question is : does this feature will solve my problem ? Will it be also merged to 1.7 branch soon ?

Thanks a lot again.

[zhenlineo]

Hi @elR1co,
Yes, this PR will allow you to set the thread count used by netty thread pool used by this driver. You will be able to give 2 threads per driver. However currently there is no plan to back port this feature into 1.7. Our 4.0 driver is ready for a final release soon. The 4.0 driver will support all in-support Neo4j versions. Though you might need to change some code as we broke some public API.

[zhenlineo]

Hi @elR1co,
The default value is 2 * availableProcessors. The 0 we used is an implementation detail. Deep down the stack, Netty will modify it to 2 * availableProcessors if it is 0. The constant is not exposed by Netty, thus we will not support the computation of processor count either. If you are interested, you can have a look at MultithreadEventLoopGroup.