| /* $Id$ */ |
| |
| /** |
| * 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.manifoldcf.crawler.system; |
| |
| import org.apache.manifoldcf.core.interfaces.*; |
| import org.apache.manifoldcf.crawler.interfaces.*; |
| import java.util.*; |
| |
| /** This class describes a cleanup document queue, which has a "stuffer" thread and many "reader" threads. |
| * The queue manages thread synchronization so that (a) the "stuffer" thread blocks until queue is empty, and |
| * (b) the "reader" threads block if queue is empty. |
| * The objects being queued are all QueuedDocumentSet objects. |
| */ |
| public class DocumentCleanupQueue |
| { |
| public static final String _rcsid = "@(#)$Id$"; |
| |
| // Since the queue has a maximum size, an ArrayList is a fine way to keep it |
| protected final List<DocumentCleanupSet> queue = new ArrayList<DocumentCleanupSet>(); |
| // This flag gets set to 'true' if the queue is being cleared due to a reset |
| protected boolean resetFlag = false; |
| |
| /** Constructor. |
| */ |
| public DocumentCleanupQueue() |
| { |
| } |
| |
| /** Wake up all threads waiting on this queue. This happens at the beginning of a reset. |
| */ |
| public void reset() |
| { |
| synchronized (queue) |
| { |
| resetFlag = true; |
| queue.notifyAll(); |
| } |
| } |
| |
| /** Clear. This is only used on reset. |
| */ |
| public void clear() |
| { |
| synchronized (queue) |
| { |
| queue.clear(); |
| resetFlag = false; |
| } |
| } |
| |
| /** Check if "empty". |
| *@param n is the low-water mark; if the number falls below this, then this method will return true. |
| */ |
| public boolean checkIfEmpty(int n) |
| { |
| synchronized (queue) |
| { |
| if (queue.size() <= n) |
| return true; |
| } |
| return false; |
| } |
| |
| /** Add a document set to the queue. This will be a set of n documents (where n is some chunk size |
| * set by experiment). |
| *@param dd is the document set. |
| */ |
| public void addDocuments(DocumentCleanupSet dd) |
| { |
| synchronized (queue) |
| { |
| queue.add(dd); |
| queue.notify(); |
| } |
| } |
| |
| /** Pull a document set off the queue, and wait if there is |
| * nothing there. |
| *@return the document. |
| */ |
| public DocumentCleanupSet getDocuments() |
| throws InterruptedException |
| { |
| synchronized (queue) |
| { |
| // If queue is empty, go to sleep |
| if (resetFlag) |
| return null; |
| |
| while (queue.size() == 0 && resetFlag == false) |
| queue.wait(); |
| |
| // If we've been awakened, there's either an entry to grab, or we've been |
| // awakened because it's time to reset. |
| if (resetFlag) |
| return null; |
| |
| // If we've been awakened, there's an entry to grab |
| DocumentCleanupSet dd = queue.remove(queue.size()-1); |
| return dd; |
| } |
| } |
| |
| |
| } |