/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements. See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership. The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied. See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

package org.apache.thrift.server;

import java.util.concurrent.ExecutorService;
import java.util.concurrent.SynchronousQueue;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;

import org.apache.thrift.TException;
import org.apache.thrift.TProcessor;
import org.apache.thrift.protocol.TProtocol;
import org.apache.thrift.transport.TServerTransport;
import org.apache.thrift.transport.TTransport;
import org.apache.thrift.transport.TTransportException;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;


/**
 * Server which uses Java's built in ThreadPool management to spawn off
 * a worker pool that
 *
 */
public class TThreadPoolServer extends TServer {
  private static final Logger LOGGER = LoggerFactory.getLogger(TThreadPoolServer.class.getName());

  public static class Args extends AbstractServerArgs<Args> {
    public int minWorkerThreads = 5;
    public int maxWorkerThreads = Integer.MAX_VALUE;
    public int stopTimeoutVal = 60;
    public TimeUnit stopTimeoutUnit = TimeUnit.SECONDS;

    public Args(TServerTransport transport) {
      super(transport);
    }

    public Args minWorkerThreads(int n) {
      minWorkerThreads = n;
      return this;
    }

    public Args maxWorkerThreads(int n) {
      maxWorkerThreads = n;
      return this;
    }
  }

  // Executor service for handling client connections
  private ExecutorService executorService_;

  // Flag for stopping the server
  private volatile boolean stopped_;

  private final TimeUnit stopTimeoutUnit;

  private final long stopTimeoutVal;

  public TThreadPoolServer(Args args) {
    super(args);

    SynchronousQueue<Runnable> executorQueue =
      new SynchronousQueue<Runnable>();

    stopTimeoutUnit = args.stopTimeoutUnit;
    stopTimeoutVal = args.stopTimeoutVal;

    executorService_ = new ThreadPoolExecutor(args.minWorkerThreads,
                                              args.maxWorkerThreads,
                                              60,
                                              TimeUnit.SECONDS,
                                              executorQueue);
  }


  public void serve() {
    try {
      serverTransport_.listen();
    } catch (TTransportException ttx) {
      LOGGER.error("Error occurred during listening.", ttx);
      return;
    }

    stopped_ = false;
    setServing(true);
    while (!stopped_) {
      int failureCount = 0;
      try {
        TTransport client = serverTransport_.accept();
        WorkerProcess wp = new WorkerProcess(client);
        executorService_.execute(wp);
      } catch (TTransportException ttx) {
        if (!stopped_) {
          ++failureCount;
          LOGGER.warn("Transport error occurred during acceptance of message.", ttx);
        }
      }
    }

    executorService_.shutdown();

    // Loop until awaitTermination finally does return without a interrupted
    // exception. If we don't do this, then we'll shut down prematurely. We want
    // to let the executorService clear it's task queue, closing client sockets
    // appropriately.
    long timeoutMS = stopTimeoutUnit.toMillis(stopTimeoutVal);
    long now = System.currentTimeMillis();
    while (timeoutMS >= 0) {
      try {
        executorService_.awaitTermination(timeoutMS, TimeUnit.MILLISECONDS);
        break;
      } catch (InterruptedException ix) {
        long newnow = System.currentTimeMillis();
        timeoutMS -= (newnow - now);
        now = newnow;
      }
    }
    setServing(false);
  }

  public void stop() {
    stopped_ = true;
    serverTransport_.interrupt();
  }

  private class WorkerProcess implements Runnable {

    /**
     * Client that this services.
     */
    private TTransport client_;

    /**
     * Default constructor.
     *
     * @param client Transport to process
     */
    private WorkerProcess(TTransport client) {
      client_ = client;
    }

    /**
     * Loops on processing a client forever
     */
    public void run() {
      TProcessor processor = null;
      TTransport inputTransport = null;
      TTransport outputTransport = null;
      TProtocol inputProtocol = null;
      TProtocol outputProtocol = null;
      try {
        processor = processorFactory_.getProcessor(client_);
        inputTransport = inputTransportFactory_.getTransport(client_);
        outputTransport = outputTransportFactory_.getTransport(client_);
        inputProtocol = inputProtocolFactory_.getProtocol(inputTransport);
        outputProtocol = outputProtocolFactory_.getProtocol(outputTransport);
        // we check stopped_ first to make sure we're not supposed to be shutting
        // down. this is necessary for graceful shutdown.
        while (!stopped_ && processor.process(inputProtocol, outputProtocol)) {}
      } catch (TTransportException ttx) {
        // Assume the client died and continue silently
      } catch (TException tx) {
        LOGGER.error("Thrift error occurred during processing of message.", tx);
      } catch (Exception x) {
        LOGGER.error("Error occurred during processing of message.", x);
      }

      if (inputTransport != null) {
        inputTransport.close();
      }

      if (outputTransport != null) {
        outputTransport.close();
      }
    }
  }
}