/**
*
* 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.regionserver;
import java.io.IOException;
import java.io.InterruptedIOException;
import java.net.ConnectException;
import java.net.SocketTimeoutException;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.hbase.classification.InterfaceAudience;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.hbase.NotServingRegionException;
import org.apache.hadoop.hbase.Server;
import org.apache.hadoop.hbase.client.RetriesExhaustedException;
import org.apache.hadoop.hbase.coordination.BaseCoordinatedStateManager;
import org.apache.hadoop.hbase.coordination.SplitLogWorkerCoordination;
import org.apache.hadoop.hbase.shaded.protobuf.generated.ZooKeeperProtos.SplitLogTask.RecoveryMode;
import org.apache.hadoop.hbase.wal.WALFactory;
import org.apache.hadoop.hbase.wal.WALSplitter;
import org.apache.hadoop.hbase.util.CancelableProgressable;
import org.apache.hadoop.hbase.util.ExceptionUtil;
import org.apache.hadoop.hbase.util.FSUtils;
import com.google.common.annotations.VisibleForTesting;
/**
* This worker is spawned in every regionserver, including master. The Worker waits for log
* splitting tasks to be put up by the {@link org.apache.hadoop.hbase.master.SplitLogManager}
* running in the master and races with other workers in other serves to acquire those tasks.
* The coordination is done via coordination engine.
* <p>
* If a worker has successfully moved the task from state UNASSIGNED to OWNED then it owns the task.
* It keeps heart beating the manager by periodically moving the task from UNASSIGNED to OWNED
* state. On success it moves the task to TASK_DONE. On unrecoverable error it moves task state to
* ERR. If it cannot continue but wants the master to retry the task then it moves the task state to
* RESIGNED.
* <p>
* The manager can take a task away from a worker by moving the task from OWNED to UNASSIGNED. In
* the absence of a global lock there is a unavoidable race here - a worker might have just finished
* its task when it is stripped of its ownership. Here we rely on the idempotency of the log
* splitting task for correctness
*/
@InterfaceAudience.Private
public class SplitLogWorker implements Runnable {
private static final Log LOG = LogFactory.getLog(SplitLogWorker.class);
Thread worker;
// thread pool which executes recovery work
private SplitLogWorkerCoordination coordination;
private Configuration conf;
private RegionServerServices server;
public SplitLogWorker(Server hserver, Configuration conf, RegionServerServices server,
TaskExecutor splitTaskExecutor) {
this.server = server;
this.conf = conf;
this.coordination =
((BaseCoordinatedStateManager) hserver.getCoordinatedStateManager())
.getSplitLogWorkerCoordination();
this.server = server;
coordination.init(server, conf, splitTaskExecutor, this);
}
public SplitLogWorker(final Server hserver, final Configuration conf,
final RegionServerServices server, final LastSequenceId sequenceIdChecker,
final WALFactory factory) {
this(server, conf, server, new TaskExecutor() {
@Override
public Status exec(String filename, RecoveryMode mode, CancelableProgressable p) {
Path walDir;
FileSystem fs;
try {
walDir = FSUtils.getWALRootDir(conf);
fs = walDir.getFileSystem(conf);
} catch (IOException e) {
LOG.warn("could not find root dir or fs", e);
return Status.RESIGNED;
}
// TODO have to correctly figure out when log splitting has been
// interrupted or has encountered a transient error and when it has
// encountered a bad non-retry-able persistent error.
try {
if (!WALSplitter.splitLogFile(walDir, fs.getFileStatus(new Path(walDir, filename)),
fs, conf, p, sequenceIdChecker, server.getCoordinatedStateManager(), mode, factory)) {
return Status.PREEMPTED;
}
} catch (InterruptedIOException iioe) {
LOG.warn("log splitting of " + filename + " interrupted, resigning", iioe);
return Status.RESIGNED;
} catch (IOException e) {
Throwable cause = e.getCause();
if (e instanceof RetriesExhaustedException && (cause instanceof NotServingRegionException
|| cause instanceof ConnectException
|| cause instanceof SocketTimeoutException)) {
LOG.warn("log replaying of " + filename + " can't connect to the target regionserver, "
+ "resigning", e);
return Status.RESIGNED;
} else if (cause instanceof InterruptedException) {
LOG.warn("log splitting of " + filename + " interrupted, resigning", e);
return Status.RESIGNED;
}
LOG.warn("log splitting of " + filename + " failed, returning error", e);
return Status.ERR;
}
return Status.DONE;
}
});
}
@Override
public void run() {
try {
LOG.info("SplitLogWorker " + server.getServerName() + " starting");
coordination.registerListener();
// wait for Coordination Engine is ready
boolean res = false;
while (!res && !coordination.isStop()) {
res = coordination.isReady();
}
if (!coordination.isStop()) {
coordination.taskLoop();
}
} catch (Throwable t) {
if (ExceptionUtil.isInterrupt(t)) {
LOG.info("SplitLogWorker interrupted. Exiting. " + (coordination.isStop() ? "" :
" (ERROR: exitWorker is not set, exiting anyway)"));
} else {
// only a logical error can cause here. Printing it out
// to make debugging easier
LOG.error("unexpected error ", t);
}
} finally {
coordination.removeListener();
LOG.info("SplitLogWorker " + server.getServerName() + " exiting");
}
}
/**
* If the worker is doing a task i.e. splitting a log file then stop the task.
* It doesn't exit the worker thread.
*/
public void stopTask() {
LOG.info("Sending interrupt to stop the worker thread");
worker.interrupt(); // TODO interrupt often gets swallowed, do what else?
}
/**
* start the SplitLogWorker thread
*/
public void start() {
worker = new Thread(null, this, "SplitLogWorker-" + server.getServerName().toShortString());
worker.start();
}
/**
* stop the SplitLogWorker thread
*/
public void stop() {
coordination.stopProcessingTasks();
stopTask();
}
/**
* Objects implementing this interface actually do the task that has been
* acquired by a {@link SplitLogWorker}. Since there isn't a water-tight
* guarantee that two workers will not be executing the same task therefore it
* is better to have workers prepare the task and then have the
* {@link org.apache.hadoop.hbase.master.SplitLogManager} commit the work in
* SplitLogManager.TaskFinisher
*/
public interface TaskExecutor {
enum Status {
DONE(),
ERR(),
RESIGNED(),
PREEMPTED()
}
Status exec(String name, RecoveryMode mode, CancelableProgressable p);
}
/**
* Returns the number of tasks processed by coordination.
* This method is used by tests only
*/
@VisibleForTesting
public int getTaskReadySeq() {
return coordination.getTaskReadySeq();
}
}