| /** |
| * Copyright 2007 The Apache Software Foundation |
| * |
| * 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.hadoop.hbase; |
| |
| import org.apache.commons.logging.Log; |
| import org.apache.commons.logging.LogFactory; |
| import org.apache.hadoop.hbase.util.Sleeper; |
| |
| /** |
| * Chore is a task performed on a period in hbase. The chore is run in its own |
| * thread. This base abstract class provides while loop and sleeping facility. |
| * If an unhandled exception, the threads exit is logged. |
| * Implementers just need to add checking if there is work to be done and if |
| * so, do it. Its the base of most of the chore threads in hbase. |
| * |
| * <p>Don't subclass Chore if the task relies on being woken up for something to |
| * do, such as an entry being added to a queue, etc. |
| */ |
| public abstract class Chore extends Thread { |
| private final Log LOG = LogFactory.getLog(this.getClass()); |
| private final Sleeper sleeper; |
| protected final Stoppable stopper; |
| |
| /** |
| * @param p Period at which we should run. Will be adjusted appropriately |
| * should we find work and it takes time to complete. |
| * @param stopper When {@link Stoppable#isStopped()} is true, this thread will |
| * cleanup and exit cleanly. |
| */ |
| public Chore(String name, final int p, final Stoppable stopper) { |
| super(name); |
| this.sleeper = new Sleeper(p, stopper); |
| this.stopper = stopper; |
| } |
| |
| /** |
| * @see java.lang.Thread#run() |
| */ |
| @Override |
| public void run() { |
| try { |
| boolean initialChoreComplete = false; |
| while (!this.stopper.isStopped()) { |
| long startTime = System.currentTimeMillis(); |
| try { |
| if (!initialChoreComplete) { |
| initialChoreComplete = initialChore(); |
| } else { |
| chore(); |
| } |
| } catch (Exception e) { |
| LOG.error("Caught exception", e); |
| if (this.stopper.isStopped()) { |
| continue; |
| } |
| } |
| this.sleeper.sleep(startTime); |
| } |
| } catch (Throwable t) { |
| LOG.fatal(getName() + "error", t); |
| } finally { |
| LOG.info(getName() + " exiting"); |
| } |
| } |
| |
| /** |
| * If the thread is currently sleeping, trigger the core to happen immediately. |
| * If it's in the middle of its operation, will begin another operation |
| * immediately after finishing this one. |
| */ |
| public void triggerNow() { |
| this.sleeper.skipSleepCycle(); |
| } |
| |
| /** |
| * Override to run a task before we start looping. |
| * @return true if initial chore was successful |
| */ |
| protected boolean initialChore() { |
| // Default does nothing. |
| return true; |
| } |
| |
| /** |
| * Look for chores. If any found, do them else just return. |
| */ |
| protected abstract void chore(); |
| |
| /** |
| * Sleep for period. |
| */ |
| protected void sleep() { |
| this.sleeper.sleep(); |
| } |
| } |