/**
*
* 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.coordination;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.atomic.AtomicLong;
import org.apache.commons.lang.math.RandomUtils;
import org.apache.commons.lang.mutable.MutableInt;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.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.HConstants;
import org.apache.hadoop.hbase.ServerName;
import org.apache.hadoop.hbase.SplitLogCounters;
import org.apache.hadoop.hbase.SplitLogTask;
import org.apache.hadoop.hbase.exceptions.DeserializationException;
import org.apache.hadoop.hbase.master.SplitLogManager;
import org.apache.hadoop.hbase.protobuf.generated.ZooKeeperProtos.RegionStoreSequenceIds;
import org.apache.hadoop.hbase.protobuf.generated.ZooKeeperProtos.SplitLogTask.RecoveryMode;
import org.apache.hadoop.hbase.regionserver.HRegion;
import org.apache.hadoop.hbase.regionserver.RegionServerServices;
import org.apache.hadoop.hbase.regionserver.SplitLogWorker;
import org.apache.hadoop.hbase.regionserver.SplitLogWorker.TaskExecutor;
import org.apache.hadoop.hbase.regionserver.handler.HLogSplitterHandler;
import org.apache.hadoop.hbase.regionserver.wal.HLogUtil;
import org.apache.hadoop.hbase.util.CancelableProgressable;
import org.apache.hadoop.hbase.util.EnvironmentEdgeManager;
import org.apache.hadoop.hbase.zookeeper.ZKSplitLog;
import org.apache.hadoop.hbase.zookeeper.ZKUtil;
import org.apache.hadoop.hbase.zookeeper.ZooKeeperListener;
import org.apache.hadoop.hbase.zookeeper.ZooKeeperWatcher;
import org.apache.hadoop.util.StringUtils;
import org.apache.zookeeper.AsyncCallback;
import org.apache.zookeeper.KeeperException;
import org.apache.zookeeper.data.Stat;
/**
* ZooKeeper based implementation of {@link SplitLogWorkerCoordination}
* It listen for changes in ZooKeeper and
*
*/
@InterfaceAudience.Private
public class ZkSplitLogWorkerCoordination extends ZooKeeperListener implements
SplitLogWorkerCoordination {
private static final Log LOG = LogFactory.getLog(ZkSplitLogWorkerCoordination.class);
private static final int checkInterval = 5000; // 5 seconds
private static final int FAILED_TO_OWN_TASK = -1;
private SplitLogWorker worker;
private TaskExecutor splitTaskExecutor;
private final Object taskReadyLock = new Object();
volatile int taskReadySeq = 0;
private volatile String currentTask = null;
private int currentVersion;
private volatile boolean shouldStop = false;
private final Object grabTaskLock = new Object();
private boolean workerInGrabTask = false;
private int reportPeriod;
private RegionServerServices server = null;
protected final AtomicInteger tasksInProgress = new AtomicInteger(0);
private int maxConcurrentTasks = 0;
private final ZkCoordinatedStateManager manager;
public ZkSplitLogWorkerCoordination(ZkCoordinatedStateManager zkCoordinatedStateManager,
ZooKeeperWatcher watcher) {
super(watcher);
manager = zkCoordinatedStateManager;
}
/**
* Override handler from {@link ZooKeeperListener}
*/
@Override
public void nodeChildrenChanged(String path) {
if (path.equals(watcher.splitLogZNode)) {
LOG.debug("tasks arrived or departed");
synchronized (taskReadyLock) {
taskReadySeq++;
taskReadyLock.notify();
}
}
}
/**
* Override handler from {@link ZooKeeperListener}
*/
@Override
public void nodeDataChanged(String path) {
// there will be a self generated dataChanged event every time attemptToOwnTask()
// heartbeats the task znode by upping its version
synchronized (grabTaskLock) {
if (workerInGrabTask) {
// currentTask can change
String taskpath = currentTask;
if (taskpath != null && taskpath.equals(path)) {
getDataSetWatchAsync();
}
}
}
}
/**
* Override setter from {@link SplitLogWorkerCoordination}
*/
@Override
public void init(RegionServerServices server, Configuration conf,
TaskExecutor splitExecutor, SplitLogWorker worker) {
this.server = server;
this.worker = worker;
this.splitTaskExecutor = splitExecutor;
maxConcurrentTasks = conf.getInt("hbase.regionserver.wal.max.splitters", DEFAULT_MAX_SPLITTERS);
reportPeriod =
conf.getInt("hbase.splitlog.report.period",
conf.getInt(HConstants.HBASE_SPLITLOG_MANAGER_TIMEOUT,
ZKSplitLogManagerCoordination.DEFAULT_TIMEOUT) / 3);
}
/* Support functions for Zookeeper async callback */
void getDataSetWatchFailure(String path) {
synchronized (grabTaskLock) {
if (workerInGrabTask) {
// currentTask can change but that's ok
String taskpath = currentTask;
if (taskpath != null && taskpath.equals(path)) {
LOG.info("retrying data watch on " + path);
SplitLogCounters.tot_wkr_get_data_retry.incrementAndGet();
getDataSetWatchAsync();
} else {
// no point setting a watch on the task which this worker is not
// working upon anymore
}
}
}
}
public void getDataSetWatchAsync() {
watcher.getRecoverableZooKeeper().getZooKeeper()
.getData(currentTask, watcher, new GetDataAsyncCallback(), null);
SplitLogCounters.tot_wkr_get_data_queued.incrementAndGet();
}
void getDataSetWatchSuccess(String path, byte[] data) {
SplitLogTask slt;
try {
slt = SplitLogTask.parseFrom(data);
} catch (DeserializationException e) {
LOG.warn("Failed parse", e);
return;
}
synchronized (grabTaskLock) {
if (workerInGrabTask) {
// currentTask can change but that's ok
String taskpath = currentTask;
if (taskpath != null && taskpath.equals(path)) {
ServerName serverName = manager.getServer().getServerName();
// have to compare data. cannot compare version because then there
// will be race with attemptToOwnTask()
// cannot just check whether the node has been transitioned to
// UNASSIGNED because by the time this worker sets the data watch
// the node might have made two transitions - from owned by this
// worker to unassigned to owned by another worker
if (!slt.isOwned(serverName) && !slt.isDone(serverName) && !slt.isErr(serverName)
&& !slt.isResigned(serverName)) {
LOG.info("task " + taskpath + " preempted from " + serverName
+ ", current task state and owner=" + slt.toString());
worker.stopTask();
}
}
}
}
}
/**
* try to grab a 'lock' on the task zk node to own and execute the task.
* <p>
* @param path zk node for the task
*/
private void grabTask(String path) {
Stat stat = new Stat();
byte[] data;
synchronized (grabTaskLock) {
currentTask = path;
workerInGrabTask = true;
if (Thread.interrupted()) {
return;
}
}
try {
try {
if ((data = ZKUtil.getDataNoWatch(watcher, path, stat)) == null) {
SplitLogCounters.tot_wkr_failed_to_grab_task_no_data.incrementAndGet();
return;
}
} catch (KeeperException e) {
LOG.warn("Failed to get data for znode " + path, e);
SplitLogCounters.tot_wkr_failed_to_grab_task_exception.incrementAndGet();
return;
}
SplitLogTask slt;
try {
slt = SplitLogTask.parseFrom(data);
} catch (DeserializationException e) {
LOG.warn("Failed parse data for znode " + path, e);
SplitLogCounters.tot_wkr_failed_to_grab_task_exception.incrementAndGet();
return;
}
if (!slt.isUnassigned()) {
SplitLogCounters.tot_wkr_failed_to_grab_task_owned.incrementAndGet();
return;
}
currentVersion =
attemptToOwnTask(true, watcher, server.getServerName(), path,
slt.getMode(), stat.getVersion());
if (currentVersion < 0) {
SplitLogCounters.tot_wkr_failed_to_grab_task_lost_race.incrementAndGet();
return;
}
if (ZKSplitLog.isRescanNode(watcher, currentTask)) {
ZkSplitLogWorkerCoordination.ZkSplitTaskDetails splitTaskDetails =
new ZkSplitLogWorkerCoordination.ZkSplitTaskDetails();
splitTaskDetails.setTaskNode(currentTask);
splitTaskDetails.setCurTaskZKVersion(new MutableInt(currentVersion));
endTask(new SplitLogTask.Done(server.getServerName(), slt.getMode()),
SplitLogCounters.tot_wkr_task_acquired_rescan, splitTaskDetails);
return;
}
LOG.info("worker " + server.getServerName() + " acquired task " + path);
SplitLogCounters.tot_wkr_task_acquired.incrementAndGet();
getDataSetWatchAsync();
submitTask(path, slt.getMode(), currentVersion, reportPeriod);
// after a successful submit, sleep a little bit to allow other RSs to grab the rest tasks
try {
int sleepTime = RandomUtils.nextInt(500) + 500;
Thread.sleep(sleepTime);
} catch (InterruptedException e) {
LOG.warn("Interrupted while yielding for other region servers", e);
Thread.currentThread().interrupt();
}
} finally {
synchronized (grabTaskLock) {
workerInGrabTask = false;
// clear the interrupt from stopTask() otherwise the next task will
// suffer
Thread.interrupted();
}
}
}
/**
* Submit a log split task to executor service
* @param curTask task to submit
* @param curTaskZKVersion current version of task
*/
void submitTask(final String curTask, final RecoveryMode mode, final int curTaskZKVersion,
final int reportPeriod) {
final MutableInt zkVersion = new MutableInt(curTaskZKVersion);
CancelableProgressable reporter = new CancelableProgressable() {
private long last_report_at = 0;
@Override
public boolean progress() {
long t = EnvironmentEdgeManager.currentTime();
if ((t - last_report_at) > reportPeriod) {
last_report_at = t;
int latestZKVersion =
attemptToOwnTask(false, watcher, server.getServerName(), curTask,
mode, zkVersion.intValue());
if (latestZKVersion < 0) {
LOG.warn("Failed to heartbeat the task" + curTask);
return false;
}
zkVersion.setValue(latestZKVersion);
}
return true;
}
};
ZkSplitLogWorkerCoordination.ZkSplitTaskDetails splitTaskDetails =
new ZkSplitLogWorkerCoordination.ZkSplitTaskDetails();
splitTaskDetails.setTaskNode(curTask);
splitTaskDetails.setCurTaskZKVersion(zkVersion);
HLogSplitterHandler hsh =
new HLogSplitterHandler(server, this, splitTaskDetails, reporter,
this.tasksInProgress, splitTaskExecutor, mode);
server.getExecutorService().submit(hsh);
}
/**
* This function calculates how many splitters it could create based on expected average tasks per
* RS and the hard limit upper bound(maxConcurrentTasks) set by configuration. <br>
* At any given time, a RS allows spawn MIN(Expected Tasks/RS, Hard Upper Bound)
* @param numTasks current total number of available tasks
*/
private int calculateAvailableSplitters(int numTasks) {
// at lease one RS(itself) available
int availableRSs = 1;
try {
List<String> regionServers =
ZKUtil.listChildrenNoWatch(watcher, watcher.rsZNode);
availableRSs = Math.max(availableRSs, (regionServers == null) ? 0 : regionServers.size());
} catch (KeeperException e) {
// do nothing
LOG.debug("getAvailableRegionServers got ZooKeeper exception", e);
}
int expectedTasksPerRS = (numTasks / availableRSs) + ((numTasks % availableRSs == 0) ? 0 : 1);
expectedTasksPerRS = Math.max(1, expectedTasksPerRS); // at least be one
// calculate how many more splitters we could spawn
return Math.min(expectedTasksPerRS, maxConcurrentTasks)
- this.tasksInProgress.get();
}
/**
* Try to own the task by transitioning the zk node data from UNASSIGNED to OWNED.
* <p>
* This method is also used to periodically heartbeat the task progress by transitioning the node
* from OWNED to OWNED.
* <p>
* @param isFirstTime shows whther it's the first attempt.
* @param zkw zk wathcer
* @param server name
* @param task to own
* @param taskZKVersion version of the task in zk
* @return non-negative integer value when task can be owned by current region server otherwise -1
*/
protected static int attemptToOwnTask(boolean isFirstTime, ZooKeeperWatcher zkw,
ServerName server, String task, RecoveryMode mode, int taskZKVersion) {
int latestZKVersion = FAILED_TO_OWN_TASK;
try {
SplitLogTask slt = new SplitLogTask.Owned(server, mode);
Stat stat = zkw.getRecoverableZooKeeper().setData(task, slt.toByteArray(), taskZKVersion);
if (stat == null) {
LOG.warn("zk.setData() returned null for path " + task);
SplitLogCounters.tot_wkr_task_heartbeat_failed.incrementAndGet();
return FAILED_TO_OWN_TASK;
}
latestZKVersion = stat.getVersion();
SplitLogCounters.tot_wkr_task_heartbeat.incrementAndGet();
return latestZKVersion;
} catch (KeeperException e) {
if (!isFirstTime) {
if (e.code().equals(KeeperException.Code.NONODE)) {
LOG.warn("NONODE failed to assert ownership for " + task, e);
} else if (e.code().equals(KeeperException.Code.BADVERSION)) {
LOG.warn("BADVERSION failed to assert ownership for " + task, e);
} else {
LOG.warn("failed to assert ownership for " + task, e);
}
}
} catch (InterruptedException e1) {
LOG.warn("Interrupted while trying to assert ownership of " + task + " "
+ StringUtils.stringifyException(e1));
Thread.currentThread().interrupt();
}
SplitLogCounters.tot_wkr_task_heartbeat_failed.incrementAndGet();
return FAILED_TO_OWN_TASK;
}
/**
* Wait for tasks to become available at /hbase/splitlog zknode. Grab a task one at a time. This
* policy puts an upper-limit on the number of simultaneous log splitting that could be happening
* in a cluster.
* <p>
* Synchronization using {@link #taskReadyLock} ensures that it will try to grab every task that
* has been put up
* @throws InterruptedException
*/
@Override
public void taskLoop() throws InterruptedException {
while (!shouldStop) {
int seq_start = taskReadySeq;
List<String> paths = null;
paths = getTaskList();
if (paths == null) {
LOG.warn("Could not get tasks, did someone remove " + watcher.splitLogZNode
+ " ... worker thread exiting.");
return;
}
// pick meta wal firstly
int offset = (int) (Math.random() * paths.size());
for (int i = 0; i < paths.size(); i++) {
if (HLogUtil.isMetaFile(paths.get(i))) {
offset = i;
break;
}
}
int numTasks = paths.size();
for (int i = 0; i < numTasks; i++) {
int idx = (i + offset) % paths.size();
// don't call ZKSplitLog.getNodeName() because that will lead to
// double encoding of the path name
if (this.calculateAvailableSplitters(numTasks) > 0) {
grabTask(ZKUtil.joinZNode(watcher.splitLogZNode, paths.get(idx)));
} else {
LOG.debug("Current region server " + server.getServerName() + " has "
+ this.tasksInProgress.get() + " tasks in progress and can't take more.");
break;
}
if (shouldStop) {
return;
}
}
SplitLogCounters.tot_wkr_task_grabing.incrementAndGet();
synchronized (taskReadyLock) {
while (seq_start == taskReadySeq) {
taskReadyLock.wait(checkInterval);
if (server != null) {
// check to see if we have stale recovering regions in our internal memory state
Map<String, HRegion> recoveringRegions = server.getRecoveringRegions();
if (!recoveringRegions.isEmpty()) {
// Make a local copy to prevent ConcurrentModificationException when other threads
// modify recoveringRegions
List<String> tmpCopy = new ArrayList<String>(recoveringRegions.keySet());
for (String region : tmpCopy) {
String nodePath =
ZKUtil.joinZNode(watcher.recoveringRegionsZNode, region);
try {
if (ZKUtil.checkExists(watcher, nodePath) == -1) {
HRegion r = recoveringRegions.remove(region);
if (r != null) {
r.setRecovering(false);
}
LOG.debug("Mark recovering region:" + region + " up.");
} else {
// current check is a defensive(or redundant) mechanism to prevent us from
// having stale recovering regions in our internal RS memory state while
// zookeeper(source of truth) says differently. We stop at the first good one
// because we should not have a single instance such as this in normal case so
// check the first one is good enough.
break;
}
} catch (KeeperException e) {
// ignore zookeeper error
LOG.debug("Got a zookeeper when trying to open a recovering region", e);
break;
}
}
}
}
}
}
}
}
private List<String> getTaskList() throws InterruptedException {
List<String> childrenPaths = null;
long sleepTime = 1000;
// It will be in loop till it gets the list of children or
// it will come out if worker thread exited.
while (!shouldStop) {
try {
childrenPaths =
ZKUtil.listChildrenAndWatchForNewChildren(watcher,
watcher.splitLogZNode);
if (childrenPaths != null) {
return childrenPaths;
}
} catch (KeeperException e) {
LOG.warn("Could not get children of znode " + watcher.splitLogZNode, e);
}
LOG.debug("Retry listChildren of znode " + watcher.splitLogZNode
+ " after sleep for " + sleepTime + "ms!");
Thread.sleep(sleepTime);
}
return childrenPaths;
}
@Override
public void markCorrupted(Path rootDir, String name, FileSystem fs) {
ZKSplitLog.markCorrupted(rootDir, name, fs);
}
@Override
public boolean isReady() throws InterruptedException {
int result = -1;
try {
result = ZKUtil.checkExists(watcher, watcher.splitLogZNode);
} catch (KeeperException e) {
// ignore
LOG.warn("Exception when checking for " + watcher.splitLogZNode
+ " ... retrying", e);
}
if (result == -1) {
LOG.info(watcher.splitLogZNode
+ " znode does not exist, waiting for master to create");
Thread.sleep(1000);
}
return (result != -1);
}
@Override
public int getTaskReadySeq() {
return taskReadySeq;
}
@Override
public void registerListener() {
watcher.registerListener(this);
}
@Override
public void removeListener() {
watcher.unregisterListener(this);
}
@Override
public void stopProcessingTasks() {
this.shouldStop = true;
}
@Override
public boolean isStop() {
return shouldStop;
}
@Override
public RegionStoreSequenceIds getRegionFlushedSequenceId(String failedServerName, String key)
throws IOException {
return ZKSplitLog.getRegionFlushedSequenceId(watcher, failedServerName, key);
}
/**
* Asynchronous handler for zk get-data-set-watch on node results.
*/
class GetDataAsyncCallback implements AsyncCallback.DataCallback {
private final Log LOG = LogFactory.getLog(GetDataAsyncCallback.class);
@Override
public void processResult(int rc, String path, Object ctx, byte[] data, Stat stat) {
SplitLogCounters.tot_wkr_get_data_result.incrementAndGet();
if (rc != 0) {
LOG.warn("getdata rc = " + KeeperException.Code.get(rc) + " " + path);
getDataSetWatchFailure(path);
return;
}
data = watcher.getRecoverableZooKeeper().removeMetaData(data);
getDataSetWatchSuccess(path, data);
}
}
/*
* Next part is related to HLogSplitterHandler
*/
/**
* endTask() can fail and the only way to recover out of it is for the {@link SplitLogManager} to
* timeout the task node.
* @param slt
* @param ctr
*/
@Override
public void endTask(SplitLogTask slt, AtomicLong ctr, SplitTaskDetails details) {
ZkSplitTaskDetails zkDetails = (ZkSplitTaskDetails) details;
String task = zkDetails.getTaskNode();
int taskZKVersion = zkDetails.getCurTaskZKVersion().intValue();
try {
if (ZKUtil.setData(watcher, task, slt.toByteArray(), taskZKVersion)) {
LOG.info("successfully transitioned task " + task + " to final state " + slt);
ctr.incrementAndGet();
return;
}
LOG.warn("failed to transistion task " + task + " to end state " + slt
+ " because of version mismatch ");
} catch (KeeperException.BadVersionException bve) {
LOG.warn("transisition task " + task + " to " + slt + " failed because of version mismatch",
bve);
} catch (KeeperException.NoNodeException e) {
LOG.fatal(
"logic error - end task " + task + " " + slt + " failed because task doesn't exist", e);
} catch (KeeperException e) {
LOG.warn("failed to end task, " + task + " " + slt, e);
}
SplitLogCounters.tot_wkr_final_transition_failed.incrementAndGet();
}
/**
* When ZK-based implementation wants to complete the task, it needs to know task znode and
* current znode cversion (needed for subsequent update operation).
*/
public static class ZkSplitTaskDetails implements SplitTaskDetails {
private String taskNode;
private MutableInt curTaskZKVersion;
public ZkSplitTaskDetails() {
}
public ZkSplitTaskDetails(String taskNode, MutableInt curTaskZKVersion) {
this.taskNode = taskNode;
this.curTaskZKVersion = curTaskZKVersion;
}
public String getTaskNode() {
return taskNode;
}
public void setTaskNode(String taskNode) {
this.taskNode = taskNode;
}
public MutableInt getCurTaskZKVersion() {
return curTaskZKVersion;
}
public void setCurTaskZKVersion(MutableInt curTaskZKVersion) {
this.curTaskZKVersion = curTaskZKVersion;
}
@Override
public String getWALFile() {
return ZKSplitLog.getFileName(taskNode);
}
}
}