/*
 * Copyright (C) 2005 Alfresco, Inc.
 *
 * Licensed under the Mozilla Public License version 1.1 
 * with a permitted attribution clause. You may obtain a
 * copy of the License at
 *
 *   http://www.alfresco.org/legal/license.txt
 *
 * 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.alfresco.filesys.server.oncrpc;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

/**
 * ONC/RPC Request Thread Pool Class
 * 
 * <p>Processes RPC requests using a pool of worker threads.
 * 
 * @author GKSpencer
 */
public class RpcRequestThreadPool {

	// Debug logging

	private static final Log logger = LogFactory.getLog(RpcRequestThreadPool.class);
	
	//	Default/minimum/maximum number of worker threads to use
	
	public static final int DefaultWorkerThreads	= 8;
	public static final int MinimumWorkerThreads	= 4;
	public static final int MaximumWorkerThreads	= 50;

	//	Queue of RPC requests
	
	private RpcRequestQueue m_queue;

	//	Worker threads
	
	private ThreadWorker[] m_workers;
	
	//	RPC dispatcher
	
	private RpcProcessor m_rpcProcessor;
	
	/**
	 * Thread Worker Inner Class
	 */
	protected class ThreadWorker implements Runnable
	{

		//	Worker thread

		private Thread mi_thread;

		//	Worker unique id

		private int mi_id;

		//	Shutdown flag

		private boolean mi_shutdown = false;

		/**
		 * Class constructor
		 * 
		 * @param name String
		 * @param id int
		 */
		public ThreadWorker(String name, int id)
		{

			//	Save the thread id

			mi_id = id;

			//	Create the worker thread

			mi_thread = new Thread(this);
			mi_thread.setName(name);
			mi_thread.setDaemon(true);
			mi_thread.start();
		}

		/**
		 * Request the worker thread to shutdown
		 */
		public final void shutdownRequest()
		{
			mi_shutdown = true;
			try
			{
				mi_thread.interrupt();
			} catch (Exception ex)
			{
			}
		}

		/**
		 * Run the thread
		 */
		public void run()
		{

			//	Loop until shutdown

			RpcPacket rpc = null;
			RpcPacket response = null;

			while (mi_shutdown == false)
			{

				try
				{

					//	Wait for an RPC request to be queued

					rpc = m_queue.removeRequest();
				} catch (InterruptedException ex)
				{

					//	Check for shutdown

					if (mi_shutdown == true)
						break;
				}

				//	If the request is valid process it

				if (rpc != null)
				{

					try
					{

						//	Process the request

						response = m_rpcProcessor.processRpc(rpc);
						if (response != null)
							response.getPacketHandler().sendRpcResponse(response);
					} catch (Throwable ex)
					{

						//	Do not display errors if shutting down

						if (mi_shutdown == false)
						{
							if ( logger.isDebugEnabled()) {
								logger.debug("Worker " + Thread.currentThread().getName() + ":");
								logger.debug(ex);
							}
						}
					} finally
					{

						//	Release the RPC packet(s) back to the packet pool

						if (rpc.getClientProtocol() == Rpc.TCP && rpc.isAllocatedFromPool())
							rpc.getOwnerPacketPool().releasePacket(rpc);

						if (response != null && response.getClientProtocol() == Rpc.TCP
								&& response.getBuffer() != rpc.getBuffer() && response.isAllocatedFromPool())
							response.getOwnerPacketPool().releasePacket(response);

					}
				}
			}
		}
	};

	/**
	 * Class constructor
	 * 
	 * @param threadName String
	 * @param rpcServer RpcProcessor
	 * @param pktHandler PacketHandlerInterface
	 */
	public RpcRequestThreadPool(String threadName, RpcProcessor rpcServer)
	{
		this(threadName, DefaultWorkerThreads, rpcServer);
	}

	/**
	 * Class constructor
	 * 
	 * @param threadName String
	 * @param poolSize int
	 * @param rpcServer RpcProcessor
	 */
	public RpcRequestThreadPool(String threadName, int poolSize, RpcProcessor rpcServer)
	{

		//	Save the RPC handler

		m_rpcProcessor = rpcServer;

		//	Create the request queue

		m_queue = new RpcRequestQueue();

		//	Check that we have at least minimum worker threads

		if (poolSize < MinimumWorkerThreads)
			poolSize = MinimumWorkerThreads;

		//	Create the worker threads

		m_workers = new ThreadWorker[poolSize];

		for (int i = 0; i < m_workers.length; i++)
			m_workers[i] = new ThreadWorker(threadName + (i + 1), i);
	}

	/**
	 * Return the number of requests in the queue
	 *
	 * @return int
	 */
	public final int getNumberOfRequests()
	{
		return m_queue.numberOfRequests();
	}

	/**
	 * Queue an RPC request to the thread pool for processing
	 *
	 * @param rpc RpcPacket
	 */
	public final void queueRpcRequest(RpcPacket pkt)
	{
		m_queue.addRequest(pkt);
	}

	/**
	 * Shutdown the thread pool and release all resources
	 */
	public void shutdownThreadPool()
	{

		//	Shutdown the worker threads

		if (m_workers != null)
		{
			for (int i = 0; i < m_workers.length; i++)
				m_workers[i].shutdownRequest();
		}
	}
}