Use FixedThreadPool as default executor

[LeoBarykin]

The problem

When creating default GrpcServer or ManagedChannel the library uses CachedThreadPool as executor. Under load it may lead to running out of available threads and starvation.

The solution

Use a FixedThreadPool as an executor and make a configuration property for number of threads in it.

Alternatives considered

Now it is only possible via manual configuring ChannelConfigurer/ServerConfigurer

Additional context

Here https://stackoverflow.com/questions/42408634/what-is-the-exact-use-of-the-executor-in-grpc-java-s-serverbuilder-does-it-just grpc developer mentions that FixedThreadPool is more appropriate approach then default one/

BTW it is my 1st feature request ever, don't be mad if I did it wrong somehow...

[ST-DDT]

I'll probably add it along with: https://github.com/yidongnan/grpc-spring-boot-starter/issues/449

[ST-DDT]

Due to time constraints I move this to the next milestone

[bestpayAmes]

this question can be resolved by GrpcServerConfigurer? @ST-DDT

[ST-DDT]

As a workaround yes. The actual implementation by this lib should probably be inside the related factories.

[pc-rshetty]

@ST-DDT when is this going to merge any idea ? Also how does the workaround with GrpcServerConfigurer look like ?