/**
*
* 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 static org.apache.hadoop.hbase.executor.EventType.RS_ZK_REGION_MERGED;
import static org.apache.hadoop.hbase.executor.EventType.RS_ZK_REGION_MERGING;
import static org.apache.hadoop.hbase.executor.EventType.RS_ZK_REQUEST_REGION_MERGE;
import java.io.IOException;
import java.util.List;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.hbase.CoordinatedStateManager;
import org.apache.hadoop.hbase.HRegionInfo;
import org.apache.hadoop.hbase.RegionTransition;
import org.apache.hadoop.hbase.ServerName;
import org.apache.hadoop.hbase.executor.EventType;
import org.apache.hadoop.hbase.regionserver.HRegion;
import org.apache.hadoop.hbase.regionserver.RegionServerServices;
import org.apache.hadoop.hbase.util.EnvironmentEdgeManager;
import org.apache.hadoop.hbase.zookeeper.ZKAssign;
import org.apache.hadoop.hbase.zookeeper.ZKUtil;
import org.apache.hadoop.hbase.zookeeper.ZooKeeperWatcher;
import org.apache.zookeeper.KeeperException;
import org.apache.zookeeper.data.Stat;
public class ZkRegionMergeCoordination implements RegionMergeCoordination {
private CoordinatedStateManager manager;
private final ZooKeeperWatcher watcher;
private static final Log LOG = LogFactory.getLog(ZkRegionMergeCoordination.class);
public ZkRegionMergeCoordination(CoordinatedStateManager manager,
ZooKeeperWatcher watcher) {
this.manager = manager;
this.watcher = watcher;
}
/**
* ZK-based implementation. Has details about whether the state transition should be reflected in
* ZK, as well as expected version of znode.
*/
public static class ZkRegionMergeDetails implements RegionMergeCoordination.RegionMergeDetails {
private int znodeVersion;
public ZkRegionMergeDetails() {
}
public int getZnodeVersion() {
return znodeVersion;
}
public void setZnodeVersion(int znodeVersion) {
this.znodeVersion = znodeVersion;
}
}
@Override
public RegionMergeDetails getDefaultDetails() {
ZkRegionMergeDetails zstd = new ZkRegionMergeDetails();
zstd.setZnodeVersion(-1);
return zstd;
}
/**
* Wait for the merging node to be transitioned from pending_merge
* to merging by master. That's how we are sure master has processed
* the event and is good with us to move on. If we don't get any update,
* we periodically transition the node so that master gets the callback.
* If the node is removed or is not in pending_merge state any more,
* we abort the merge.
* @throws IOException
*/
@Override
public void waitForRegionMergeTransaction(RegionServerServices services,
HRegionInfo mergedRegionInfo, HRegion region_a, HRegion region_b, RegionMergeDetails details)
throws IOException {
try {
int spins = 0;
Stat stat = new Stat();
ServerName expectedServer = manager.getServer().getServerName();
String node = mergedRegionInfo.getEncodedName();
ZkRegionMergeDetails zdetails = (ZkRegionMergeDetails) details;
while (!(manager.getServer().isStopped() || services.isStopping())) {
if (spins % 5 == 0) {
LOG.debug("Still waiting for master to process " + "the pending_merge for " + node);
ZkRegionMergeDetails zrmd = (ZkRegionMergeDetails) getDefaultDetails();
transitionMergingNode(mergedRegionInfo, region_a.getRegionInfo(),
region_b.getRegionInfo(), expectedServer, zrmd, RS_ZK_REQUEST_REGION_MERGE,
RS_ZK_REQUEST_REGION_MERGE);
}
Thread.sleep(100);
spins++;
byte[] data = ZKAssign.getDataNoWatch(watcher, node, stat);
if (data == null) {
throw new IOException("Data is null, merging node " + node + " no longer exists");
}
RegionTransition rt = RegionTransition.parseFrom(data);
EventType et = rt.getEventType();
if (et == RS_ZK_REGION_MERGING) {
ServerName serverName = rt.getServerName();
if (!serverName.equals(expectedServer)) {
throw new IOException("Merging node " + node + " is for " + serverName + ", not us "
+ expectedServer);
}
byte[] payloadOfMerging = rt.getPayload();
List<HRegionInfo> mergingRegions =
HRegionInfo.parseDelimitedFrom(payloadOfMerging, 0, payloadOfMerging.length);
assert mergingRegions.size() == 3;
HRegionInfo a = mergingRegions.get(1);
HRegionInfo b = mergingRegions.get(2);
HRegionInfo hri_a = region_a.getRegionInfo();
HRegionInfo hri_b = region_b.getRegionInfo();
if (!(hri_a.equals(a) && hri_b.equals(b))) {
throw new IOException("Merging node " + node + " is for " + a + ", " + b
+ ", not expected regions: " + hri_a + ", " + hri_b);
}
// Master has processed it.
zdetails.setZnodeVersion(stat.getVersion());
return;
}
if (et != RS_ZK_REQUEST_REGION_MERGE) {
throw new IOException("Merging node " + node + " moved out of merging to " + et);
}
}
// Server is stopping/stopped
throw new IOException("Server is " + (services.isStopping() ? "stopping" : "stopped"));
} catch (Exception e) {
if (e instanceof InterruptedException) {
Thread.currentThread().interrupt();
}
throw new IOException("Failed getting MERGING znode on "
+ mergedRegionInfo.getRegionNameAsString(), e);
}
}
/**
* Creates a new ephemeral node in the PENDING_MERGE state for the merged region.
* Create it ephemeral in case regionserver dies mid-merge.
*
* <p>
* Does not transition nodes from other states. If a node already exists for
* this region, a {@link org.apache.zookeeper.KeeperException.NodeExistsException} will be thrown.
*
* @param region region to be created as offline
* @param serverName server event originates from
* @throws IOException
*/
@Override
public void startRegionMergeTransaction(final HRegionInfo region, final ServerName serverName,
final HRegionInfo a, final HRegionInfo b) throws IOException {
LOG.debug(watcher.prefix("Creating ephemeral node for " + region.getEncodedName()
+ " in PENDING_MERGE state"));
byte[] payload = HRegionInfo.toDelimitedByteArray(region, a, b);
RegionTransition rt =
RegionTransition.createRegionTransition(RS_ZK_REQUEST_REGION_MERGE, region.getRegionName(),
serverName, payload);
String node = ZKAssign.getNodeName(watcher, region.getEncodedName());
try {
if (!ZKUtil.createEphemeralNodeAndWatch(watcher, node, rt.toByteArray())) {
throw new IOException("Failed create of ephemeral " + node);
}
} catch (KeeperException e) {
throw new IOException(e);
}
}
/*
* (non-Javadoc)
* @see
* org.apache.hadoop.hbase.regionserver.coordination.RegionMergeCoordination#clean(org.apache.hadoop
* .hbase.Server, org.apache.hadoop.hbase.HRegionInfo)
*/
@Override
public void clean(final HRegionInfo hri) {
try {
// Only delete if its in expected state; could have been hijacked.
if (!ZKAssign.deleteNode(watcher, hri.getEncodedName(), RS_ZK_REQUEST_REGION_MERGE, manager
.getServer().getServerName())) {
ZKAssign.deleteNode(watcher, hri.getEncodedName(), RS_ZK_REGION_MERGING, manager
.getServer().getServerName());
}
} catch (KeeperException.NoNodeException e) {
LOG.info("Failed cleanup zk node of " + hri.getRegionNameAsString(), e);
} catch (KeeperException e) {
manager.getServer().abort("Failed cleanup zk node of " + hri.getRegionNameAsString(), e);
}
}
/*
* ZooKeeper implementation of finishRegionMergeTransaction
*/
@Override
public void completeRegionMergeTransaction(final RegionServerServices services,
HRegionInfo mergedRegionInfo, HRegion region_a, HRegion region_b, RegionMergeDetails rmd,
HRegion mergedRegion) throws IOException {
ZkRegionMergeDetails zrmd = (ZkRegionMergeDetails) rmd;
if (manager.getServer() == null
|| manager.getServer().getCoordinatedStateManager() == null) {
return;
}
// Tell master about merge by updating zk. If we fail, abort.
try {
transitionMergingNode(mergedRegionInfo, region_a.getRegionInfo(), region_b.getRegionInfo(),
manager.getServer().getServerName(), rmd, RS_ZK_REGION_MERGING, RS_ZK_REGION_MERGED);
long startTime = EnvironmentEdgeManager.currentTime();
int spins = 0;
// Now wait for the master to process the merge. We know it's done
// when the znode is deleted. The reason we keep tickling the znode is
// that it's possible for the master to miss an event.
do {
if (spins % 10 == 0) {
LOG.debug("Still waiting on the master to process the merge for "
+ mergedRegionInfo.getEncodedName() + ", waited "
+ (EnvironmentEdgeManager.currentTime() - startTime) + "ms");
}
Thread.sleep(100);
// When this returns -1 it means the znode doesn't exist
transitionMergingNode(mergedRegionInfo, region_a.getRegionInfo(), region_b.getRegionInfo(),
manager.getServer().getServerName(), rmd, RS_ZK_REGION_MERGED, RS_ZK_REGION_MERGED);
spins++;
} while (zrmd.getZnodeVersion() != -1 && !manager.getServer().isStopped()
&& !services.isStopping());
} catch (Exception e) {
if (e instanceof InterruptedException) {
Thread.currentThread().interrupt();
}
throw new IOException("Failed telling master about merge "
+ mergedRegionInfo.getEncodedName(), e);
}
// Leaving here, the mergedir with its dross will be in place but since the
// merge was successful, just leave it; it'll be cleaned when region_a is
// cleaned up by CatalogJanitor on master
}
/*
* Zookeeper implementation of region merge confirmation
*/
@Override
public void confirmRegionMergeTransaction(HRegionInfo merged, HRegionInfo a, HRegionInfo b,
ServerName serverName, RegionMergeDetails rmd) throws IOException {
transitionMergingNode(merged, a, b, serverName, rmd, RS_ZK_REGION_MERGING,
RS_ZK_REGION_MERGING);
}
/*
* Zookeeper implementation of region merge processing
*/
@Override
public void processRegionMergeRequest(HRegionInfo p, HRegionInfo hri_a, HRegionInfo hri_b,
ServerName sn, RegionMergeDetails rmd) throws IOException {
transitionMergingNode(p, hri_a, hri_b, sn, rmd, EventType.RS_ZK_REQUEST_REGION_MERGE,
EventType.RS_ZK_REGION_MERGING);
}
/**
* Transitions an existing ephemeral node for the specified region which is
* currently in the begin state to be in the end state. Master cleans up the
* final MERGE znode when it reads it (or if we crash, zk will clean it up).
*
* <p>
* Does not transition nodes from other states. If for some reason the node
* could not be transitioned, the method returns -1. If the transition is
* successful, the version of the node after transition is updated in details.
*
* <p>
* This method can fail and return false for three different reasons:
* <ul>
* <li>Node for this region does not exist</li>
* <li>Node for this region is not in the begin state</li>
* <li>After verifying the begin state, update fails because of wrong version
* (this should never actually happen since an RS only does this transition
* following a transition to the begin state. If two RS are conflicting, one would
* fail the original transition to the begin state and not this transition)</li>
* </ul>
*
* <p>
* Does not set any watches.
*
* <p>
* This method should only be used by a RegionServer when merging two regions.
*
* @param merged region to be transitioned to opened
* @param a merging region A
* @param b merging region B
* @param serverName server event originates from
* @param rmd region merge details
* @param beginState the expected current state the node should be
* @param endState the state to be transition to
* @throws IOException
*/
private void transitionMergingNode(HRegionInfo merged, HRegionInfo a, HRegionInfo b,
ServerName serverName, RegionMergeDetails rmd, final EventType beginState,
final EventType endState) throws IOException {
ZkRegionMergeDetails zrmd = (ZkRegionMergeDetails) rmd;
byte[] payload = HRegionInfo.toDelimitedByteArray(merged, a, b);
try {
zrmd.setZnodeVersion(ZKAssign.transitionNode(watcher, merged, serverName, beginState,
endState, zrmd.getZnodeVersion(), payload));
} catch (KeeperException e) {
throw new IOException(e);
}
}
}