Examples of com.facebook.presto.jdbc.internal.netty.channel.socket.nio.NioClientSocketChannelFactory

• com.facebook.presto.jdbc.internal.netty.channel.socket.nio.NioClientSocketChannelFactory
  A {@link ClientSocketChannelFactory} which creates a client-side NIO-based{@link SocketChannel}. It utilizes the non-blocking I/O mode which was introduced with NIO to serve many number of concurrent connections efficiently.

  How threads work

  There are two types of threads in a {@link NioClientSocketChannelFactory}; one is boss thread and the other is worker thread.

  Boss thread

  One {@link NioClientSocketChannelFactory} has one boss thread. It makesa connection attempt on request. Once a connection attempt succeeds, the boss thread passes the connected {@link Channel} to one of the workerthreads that the {@link NioClientSocketChannelFactory} manages.

  Worker threads

  One {@link NioClientSocketChannelFactory} can have one or more workerthreads. A worker thread performs non-blocking read and write for one or more {@link Channel}s in a non-blocking mode.

  Life cycle of threads and graceful shutdown

  All threads are acquired from the {@link Executor}s which were specified when a {@link NioClientSocketChannelFactory} was created. A boss thread isacquired from the {@code bossExecutor}, and worker threads are acquired from the {@code workerExecutor}. Therefore, you should make sure the specified {@link Executor}s are able to lend the sufficient number of threads. It is the best bet to specify {@linkplain Executors#newCachedThreadPool() a cached thread pool}.

  Both boss and worker threads are acquired lazily, and then released when there's nothing left to process. All the related resources such as {@link Selector} are also released when the boss and worker threads arereleased. Therefore, to shut down a service gracefully, you should do the following:

  1. close all channels created by the factory usually using {@link ChannelGroup#close()}, and
  2. call {@link #releaseExternalResources()}.

  Please make sure not to shut down the executor until all channels are closed. Otherwise, you will end up with a {@link RejectedExecutionException}and the related resources might not be released properly. @apiviz.landmark

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