content: /*
   * Copyright (C) 2016-2023 ActionTech.
   * based on code by MyCATCopyrightHolder Copyright (c) 2013, OpenCloudDB/MyCAT.
   * License: http://www.gnu.org/licenses/gpl.html GPL version 2 or higher.
   */
  package com.actiontech.dble.net.impl.nio;
  
  import com.actiontech.dble.DbleServer;
  import com.actiontech.dble.net.IOProcessor;
  import com.actiontech.dble.net.SocketAcceptor;
  import com.actiontech.dble.net.connection.AbstractConnection;
  import com.actiontech.dble.net.connection.FrontendConnection;
  import com.actiontech.dble.net.factory.FrontendConnectionFactory;
  import com.actiontech.dble.util.SelectorUtil;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import java.io.IOException;
  import java.net.InetSocketAddress;
  import java.net.Socket;
  import java.net.StandardSocketOptions;
  import java.nio.channels.*;
  import java.util.Map;
  import java.util.Optional;
  import java.util.Set;
  import java.util.concurrent.ConcurrentLinkedQueue;
  import java.util.concurrent.TimeUnit;
  import java.util.stream.Collectors;
  
  /**
   * @author mycat
   */
  public final class NIOAcceptor extends Thread implements SocketAcceptor {
      private static final Logger LOGGER = LoggerFactory.getLogger(NIOAcceptor.class);
      private static final AcceptIdGenerator ID_GENERATOR = new AcceptIdGenerator();
  
      private final int port;
      private Selector selector;
      private final ServerSocketChannel serverChannel;
      private final FrontendConnectionFactory factory;
      private ConcurrentLinkedQueue<AbstractConnection> frontRegisterQueue;
  
      public NIOAcceptor(String name, String bindIp, int port, int backlog, FrontendConnectionFactory factory,
                         ConcurrentLinkedQueue<AbstractConnection> frontRegisterQueue) throws IOException {
          super.setName(name);
          this.port = port;
          this.selector = Selector.open();
          this.serverChannel = ServerSocketChannel.open();
          this.serverChannel.configureBlocking(false);
          //set TCP option
          serverChannel.setOption(StandardSocketOptions.SO_REUSEADDR, true);
          serverChannel.setOption(StandardSocketOptions.SO_RCVBUF, 1024 * 16 * 2);
          serverChannel.bind(new InetSocketAddress(bindIp, port), backlog);
          this.serverChannel.register(selector, SelectionKey.OP_ACCEPT);
          this.factory = factory;
          this.frontRegisterQueue = frontRegisterQueue;
      }
  
      public int getPort() {
          return port;
      }
  
      @Override
      public void run() {
          Selector tSelector = this.selector;
          int selectReturnsImmediately = 0;
          // use 80% of the timeout for measure
          long minSelectTimeout = TimeUnit.MILLISECONDS.toNanos(SelectorUtil.DEFAULT_SELECT_TIMEOUT) / 100 * 80;
          for (; ; ) {
              try {
                  long beforeSelect = System.nanoTime();
                  int selected = tSelector.select(SelectorUtil.DEFAULT_SELECT_TIMEOUT);
  
                  //issue - https://bugs.java.com/bugdatabase/view_bug.do?bug_id=6403933
                  //refer to https://github.com/netty/netty/pull/565
                  if (selected == 0) {
                      long timeBlocked = System.nanoTime() - beforeSelect;
                      boolean checkSelectReturnsImmediately = SelectorUtil.checkSelectReturnsImmediately(timeBlocked, tSelector, minSelectTimeout);
                      if (checkSelectReturnsImmediately) {
                          selectReturnsImmediately++;
                      } else {
                          selectReturnsImmediately = 0;
                      }
                      if (selectReturnsImmediately == 1024) {
                          // The selector returned immediately for 10 times in a row,
                          // so recreate one selector as it seems like we hit the
                          // famous epoll(..) jdk bug.
                          Selector rebuildSelector = SelectorUtil.rebuildSelector(this.selector);
                          if (null != rebuildSelector) {
                              this.selector = rebuildSelector;
                          }
                          tSelector = this.selector;
                          selectReturnsImmediately = 0;
                          // try to select again
                          continue;
                      }
                  } else {
                      selectReturnsImmediately = 0;
                  }
  
                  Set<SelectionKey> keys = tSelector.selectedKeys();
                  try {
                      for (SelectionKey key : keys) {
                          if (key.isValid() && key.isAcceptable()) {
                              accept();
                          } else {
                              key.cancel();
                          }
                      }
                  } catch (final Throwable e) {
                      LOGGER.warn("caught Throwable err: ", e);
                  } finally {
                      keys.clear();
                  }
              } catch (Throwable e) {
                  LOGGER.info(getName(), e);
              }
          }
      }
  
      private void accept() {
          SocketChannel channel = null;
          try {
              channel = serverChannel.accept();
              channel.configureBlocking(false);
              NIOSocketWR socketWR = new NIOSocketWR();
              FrontendConnection c = factory.make(channel, socketWR);
              socketWR.initFromConnection(c);
              c.setId(ID_GENERATOR.getId());
              IOProcessor processor = DbleServer.getInstance().nextFrontProcessor();
              c.setProcessor(processor);
  
              frontRegisterQueue.offer(c);
              wakeupFrontedSelector();
  
          } catch (Exception e) {
              //if this exception is "SocketException: Invalid argument." , maybe you are doing setOption when the frontendConnection was closed by peer. In most of those cases , you are using SLB/LVS on MACOS, just ignore it.
              LOGGER.info(getName(), e);
              closeChannel(channel);
          }
      }
  
      private static void closeChannel(SocketChannel channel) {
          if (channel == null) {
              return;
          }
          Socket socket = channel.socket();
          if (socket != null) {
              try {
                  socket.close();
              } catch (IOException e) {
                  LOGGER.info("closeChannelError", e);
              }
          }
          try {
              channel.close();
          } catch (IOException e) {
              LOGGER.info("closeChannelError", e);
          }
      }
  
      //wakeup selector
      private void wakeupFrontedSelector() {
          Map<Thread, Runnable> threadRunnableMap = DbleServer.getInstance().getRunnableMap().get(DbleServer.NIO_FRONT_RW);
          Map<Runnable, Integer> runnableMap = threadRunnableMap.entrySet().stream().collect(Collectors.toMap(Map.Entry::getValue, entry -> ((RW) entry.getValue()).getSelectorKeySize()));
          Optional<Map.Entry<Runnable, Integer>> min = runnableMap.entrySet().stream().min(Map.Entry.comparingByValue());
          if (min.isPresent()) {
              ((RW) min.get().getKey()).wakeUpSelector();
          } else {
              LOGGER.warn("wakeupFrontedSelector error");
          }
      }
  
      /**
       * @author mycat
       */
      private static class AcceptIdGenerator {
  
          private static final long MAX_VALUE = 0xffffffffL;
  
          private long acceptId = 0L;
          private final Object lock = new Object();
  
          private long getId() {
              synchronized (lock) {
                  if (acceptId >= MAX_VALUE) {
                      acceptId = 0L;
                  }
                  return ++acceptId;
              }
          }
      }
  
  }
  