AsyncClientBuilder cleanup

[zoewangg]

Various AsynClientBuilder clean up.

• Drop async prefix in the builder(but we are gonna need to cast the httpClient builder in SdkDefaultClientBuilder see comments in the PR)
• Validate duration are positive.
• Create SdkEventLoopGroup as wrapper class to hold EventLoopGroup and ChannelFactory to be used for Netty client.

Here's how NettyNioAsyncHttpClient configuration looks like:

• using custom EventLoopGroup and channel factory

    SdkAsyncHttpClient customClient =
        NettyNioAsyncHttpClient.builder()
                               .eventLoopGroup(SdkEventLoopGroup.create(eventLoopGroup, NioSocketChannel::new))
                               .build();

• using SDK-managed eventLoopGroup but providing configurations

    SdkAsyncHttpClient customClient =
        NettyNioAsyncHttpClient.builder()
                               .eventLoopGroupBuilder(SdkEventLoopGroup.builder()
                                                                       .threadFactory(threadFactory)
                                                                       .numberOfThreads(threadCount))
                               .build();

Notes

• Now there are two different ways to create SdkEventLoopGroup
  • using SdkEventLoopGroup.create(eventLoopGroup, channelFactory)
  • using SdkEventLoopGroup.builder() and the builder doesn't have eventLoopGroup() interface defined.

This might be confusing to customers and I considered moving the builder to a different class but I find keeping them in the same class helps discoverability.

• .eventLoopGroupBuilder() is taking the builder class as parameter

[zoewangg]

we have to cast it here since SdkDefaultClientBuilder implements both SdkAsyncClientBuilder and SdkSyncClientBuilder and has overloads of httpClientBuilder for async and sync. I think this is fine as SdkDefaultClientBuilder is protected api

[shorea]

How many event loops could an event loop group if an event loop could group loops? ;)

[zoewangg]

Haha, what a tongue twister!

[shorea]

Missing t

[shorea]

Do we need to have fields for number of threads and thread factory or can we just use them to create an event loop group at build time?

[zoewangg]

I was thinking customers can retrieve the value by calling numberOfThreads(). But that's not necessary and can be confusing to customers who use SdkEventLoopGroup.create method to create the class. Removed.

[shorea]

Do we still need this?

[zoewangg]

Good catch. Updated SharedSdkEventLoopGroup to store SdkEventLoopGroup so that we can get default channel factory associated with the default event loop group.

[shorea]

Maybe an overload for the channel class that creates the reflective factory