@Override
      public void run(Object parameter) {
        setCancelled(call);
        if (channel != null) {
          channel.pipeline().fireUserEventTriggered(new CallEvent(CANCELLED, call));
        }
      }
RPC connection implementation based on netty.
<p/>
Most operations are executed in handlers. Netty handler is always executed in the same
thread(EventLoop) so no lock is needed.
<p/>
<strong>Implementation assumptions:</strong> All the private methods should be called in the
{@link #eventLoop} thread, otherwise there will be races.
@since 2.0.0
hbase-client/src/main/java/org/apache/hadoop/hbase/ipc/NettyRpcConnection.java