001/*
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *     http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018package org.apache.hadoop.hbase.regionserver;
019
020import java.io.FileNotFoundException;
021import java.io.IOException;
022import java.io.InterruptedIOException;
023import java.net.ConnectException;
024import java.net.SocketTimeoutException;
025import org.apache.hadoop.conf.Configuration;
026import org.apache.hadoop.fs.FileSystem;
027import org.apache.hadoop.fs.Path;
028import org.apache.hadoop.hbase.NotServingRegionException;
029import org.apache.hadoop.hbase.Server;
030import org.apache.hadoop.hbase.client.RetriesExhaustedException;
031import org.apache.hadoop.hbase.coordination.SplitLogWorkerCoordination;
032import org.apache.hadoop.hbase.regionserver.SplitLogWorker.TaskExecutor.Status;
033import org.apache.hadoop.hbase.util.CancelableProgressable;
034import org.apache.hadoop.hbase.util.CommonFSUtils;
035import org.apache.hadoop.hbase.util.ExceptionUtil;
036import org.apache.hadoop.hbase.wal.WALFactory;
037import org.apache.hadoop.hbase.wal.WALSplitter;
038import org.apache.yetus.audience.InterfaceAudience;
039import org.slf4j.Logger;
040import org.slf4j.LoggerFactory;
041
042/**
043 * This worker is spawned in every regionserver, including master. The Worker waits for log
044 * splitting tasks to be put up by the {@link org.apache.hadoop.hbase.master.SplitLogManager}
045 * running in the master and races with other workers in other serves to acquire those tasks.
046 * The coordination is done via coordination engine.
047 * <p>
048 * If a worker has successfully moved the task from state UNASSIGNED to OWNED then it owns the task.
049 * It keeps heart beating the manager by periodically moving the task from UNASSIGNED to OWNED
050 * state. On success it moves the task to TASK_DONE. On unrecoverable error it moves task state to
051 * ERR. If it cannot continue but wants the master to retry the task then it moves the task state to
052 * RESIGNED.
053 * <p>
054 * The manager can take a task away from a worker by moving the task from OWNED to UNASSIGNED. In
055 * the absence of a global lock there is a unavoidable race here - a worker might have just finished
056 * its task when it is stripped of its ownership. Here we rely on the idempotency of the log
057 * splitting task for correctness
058 * @deprecated since 2.4.0 and in 3.0.0, to be removed in 4.0.0, replaced by procedure-based
059 *   distributed WAL splitter, see SplitWALRemoteProcedure
060 */
061@Deprecated
062@InterfaceAudience.Private
063public class SplitLogWorker implements Runnable {
064
065  private static final Logger LOG = LoggerFactory.getLogger(SplitLogWorker.class);
066
067  Thread worker;
068  // thread pool which executes recovery work
069  private final SplitLogWorkerCoordination coordination;
070  private final Configuration conf;
071  private final RegionServerServices server;
072
073  public SplitLogWorker(Server hserver, Configuration conf, RegionServerServices server,
074      TaskExecutor splitTaskExecutor) {
075    this.server = server;
076    // Unused.
077    this.conf = conf;
078    this.coordination = hserver.getCoordinatedStateManager().getSplitLogWorkerCoordination();
079    coordination.init(server, conf, splitTaskExecutor, this);
080  }
081
082  public SplitLogWorker(Configuration conf, RegionServerServices server,
083      LastSequenceId sequenceIdChecker, WALFactory factory) {
084    this(server, conf, server, (f, p) -> splitLog(f, p, conf, server, sequenceIdChecker, factory));
085  }
086
087  /**
088   * @return Result either DONE, RESIGNED, or ERR.
089   */
090  static Status splitLog(String filename, CancelableProgressable p, Configuration conf,
091      RegionServerServices server, LastSequenceId sequenceIdChecker, WALFactory factory) {
092    Path walDir;
093    FileSystem fs;
094    try {
095      walDir = CommonFSUtils.getWALRootDir(conf);
096      fs = walDir.getFileSystem(conf);
097    } catch (IOException e) {
098      LOG.warn("Resigning, could not find root dir or fs", e);
099      return Status.RESIGNED;
100    }
101    // TODO have to correctly figure out when log splitting has been
102    // interrupted or has encountered a transient error and when it has
103    // encountered a bad non-retry-able persistent error.
104    try {
105      SplitLogWorkerCoordination splitLogWorkerCoordination =
106         server.getCoordinatedStateManager() == null ? null
107             : server.getCoordinatedStateManager().getSplitLogWorkerCoordination();
108      if (!WALSplitter.splitLogFile(walDir, fs.getFileStatus(new Path(walDir, filename)), fs, conf,
109          p, sequenceIdChecker, splitLogWorkerCoordination, factory, server)) {
110        return Status.PREEMPTED;
111      }
112    } catch (InterruptedIOException iioe) {
113      LOG.warn("Resigning, interrupted splitting WAL {}", filename, iioe);
114      return Status.RESIGNED;
115    } catch (IOException e) {
116      if (e instanceof FileNotFoundException) {
117        // A wal file may not exist anymore. Nothing can be recovered so move on
118        LOG.warn("Done, WAL {} does not exist anymore", filename, e);
119        return Status.DONE;
120      }
121      Throwable cause = e.getCause();
122      if (e instanceof RetriesExhaustedException && (cause instanceof NotServingRegionException
123          || cause instanceof ConnectException || cause instanceof SocketTimeoutException)) {
124        LOG.warn("Resigning, can't connect to target regionserver splitting WAL {}", filename, e);
125        return Status.RESIGNED;
126      } else if (cause instanceof InterruptedException) {
127        LOG.warn("Resigning, interrupted splitting WAL {}", filename, e);
128        return Status.RESIGNED;
129      }
130      LOG.warn("Error splitting WAL {}", filename, e);
131      return Status.ERR;
132    }
133    LOG.debug("Done splitting WAL {}", filename);
134    return Status.DONE;
135  }
136
137
138  @Override
139  public void run() {
140    try {
141      LOG.info("SplitLogWorker " + server.getServerName() + " starting");
142      coordination.registerListener();
143      // wait for Coordination Engine is ready
144      boolean res = false;
145      while (!res && !coordination.isStop()) {
146        res = coordination.isReady();
147      }
148      if (!coordination.isStop()) {
149        coordination.taskLoop();
150      }
151    } catch (Throwable t) {
152      if (ExceptionUtil.isInterrupt(t)) {
153        LOG.info("SplitLogWorker interrupted. Exiting. " + (coordination.isStop() ? "" :
154            " (ERROR: exitWorker is not set, exiting anyway)"));
155      } else {
156        // only a logical error can cause here. Printing it out
157        // to make debugging easier
158        LOG.error("unexpected error ", t);
159      }
160    } finally {
161      coordination.removeListener();
162      LOG.info("SplitLogWorker " + server.getServerName() + " exiting");
163    }
164  }
165
166  /**
167   * If the worker is doing a task i.e. splitting a log file then stop the task.
168   * It doesn't exit the worker thread.
169   */
170  public void stopTask() {
171    LOG.info("Sending interrupt to stop the worker thread");
172    worker.interrupt(); // TODO interrupt often gets swallowed, do what else?
173  }
174
175  /**
176   * start the SplitLogWorker thread
177   */
178  public void start() {
179    worker = new Thread(null, this, "SplitLogWorker-" + server.getServerName().toShortString());
180    worker.start();
181  }
182
183  /**
184   * stop the SplitLogWorker thread
185   */
186  public void stop() {
187    coordination.stopProcessingTasks();
188    stopTask();
189  }
190
191  /**
192   * Objects implementing this interface actually do the task that has been
193   * acquired by a {@link SplitLogWorker}. Since there isn't a water-tight
194   * guarantee that two workers will not be executing the same task therefore it
195   * is better to have workers prepare the task and then have the
196   * {@link org.apache.hadoop.hbase.master.SplitLogManager} commit the work in
197   * SplitLogManager.TaskFinisher
198   */
199  public interface TaskExecutor {
200    enum Status {
201      DONE(),
202      ERR(),
203      RESIGNED(),
204      PREEMPTED()
205    }
206    Status exec(String name, CancelableProgressable p);
207  }
208
209  /**
210   * Returns the number of tasks processed by coordination.
211   * This method is used by tests only
212   */
213  public int getTaskReadySeq() {
214    return coordination.getTaskReadySeq();
215  }
216}