Motivation

Do not block user threads when performing async thin client operations.

IEP-51 introduced async API to the Java thin client, but socket writes are still performed on the user thread and are potentially blocking.

Description

Potential approaches to this are:

1. GridNioServer
   • Pros:
     • Easy to use, provides Future-based API
     • No extra dependencies
     • Supports multiplexing (shared worker thread group across multiple connections)
   • Cons:
     • Possibly not future proof - Ignite 3.0 may change how GridNioServer works and/or switch to Netty
2. Netty
   • Pros:
     • Easy to use, provides Future-based API
     • Supports multiplexing (shared worker thread group (EventLoopGroup) across multiple connections)
     • Proven performance
   • Cons:
     • New dependency in core module
3. Perform writes in a separate thread (use dedicated thread or ForkJoinPool.commonPool)
   • Pros:
     • No dependencies
   • Cons:
     • Increased resource usage,
     • More manual thread management - hard to get right and fast
4. AsynchronousSocketChannel
   • Pros:
     • Native Java API, no dependencies
   • Cons:
     • SSL is very hard, making this approach not an option. See README: https://github.com/raell2/SSLAsynchronousSocketChannel

As a result of dev list discussions (see links below), it is decided to use GridNioServer. To make the integration clean and easy to replace with a different implementation, a couple of facade interfaces are introduced:

• ClientConnectionMultiplexer
  • void start()
  • void stop()
  • ClientConnection open(InetSocketAddress addr, Consumer<ByteBuffer> hnd)
• ClientConnection
  • CompletableFuture sendAsync(ByteBuffer msg)

Discussion Links

• http://apache-ignite-developers.2346864.n4.nabble.com/DISCUSS-Use-Netty-for-Java-thin-client-td49732.html
• http://apache-ignite-developers.2346864.n4.nabble.com/DISCUSS-Use-GridNioServer-in-Java-thin-client-td50046.html

Tickets

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