/*
*
* 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.replication;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.CopyOnWriteArrayList;
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.hbase.Abortable;
import org.apache.hadoop.hbase.Stoppable;
import org.apache.hadoop.hbase.zookeeper.ZKUtil;
import org.apache.hadoop.hbase.zookeeper.ZooKeeperListener;
import org.apache.hadoop.hbase.zookeeper.ZooKeeperWatcher;
import org.apache.zookeeper.KeeperException;
/**
* This class is a ZooKeeper implementation of the ReplicationTracker interface. This class is
* responsible for handling replication events that are defined in the ReplicationListener
* interface.
*/
@InterfaceAudience.Private
public class ReplicationTrackerZKImpl extends ReplicationStateZKBase implements ReplicationTracker {
private static final Log LOG = LogFactory.getLog(ReplicationTrackerZKImpl.class);
// All about stopping
private final Stoppable stopper;
// listeners to be notified
private final List<ReplicationListener> listeners = new CopyOnWriteArrayList<>();
// List of all the other region servers in this cluster
private final ArrayList<String> otherRegionServers = new ArrayList<>();
private final ReplicationPeers replicationPeers;
public ReplicationTrackerZKImpl(ZooKeeperWatcher zookeeper,
final ReplicationPeers replicationPeers, Configuration conf, Abortable abortable,
Stoppable stopper) {
super(zookeeper, conf, abortable);
this.replicationPeers = replicationPeers;
this.stopper = stopper;
this.zookeeper.registerListener(new OtherRegionServerWatcher(this.zookeeper));
this.zookeeper.registerListener(new PeersWatcher(this.zookeeper));
}
@Override
public void registerListener(ReplicationListener listener) {
listeners.add(listener);
}
@Override
public void removeListener(ReplicationListener listener) {
listeners.remove(listener);
}
/**
* Return a snapshot of the current region servers.
*/
@Override
public List<String> getListOfRegionServers() {
refreshOtherRegionServersList();
List<String> list = null;
synchronized (otherRegionServers) {
list = new ArrayList<>(otherRegionServers);
}
return list;
}
/**
* Watcher used to be notified of the other region server's death in the local cluster. It
* initiates the process to transfer the queues if it is able to grab the lock.
*/
public class OtherRegionServerWatcher extends ZooKeeperListener {
/**
* Construct a ZooKeeper event listener.
*/
public OtherRegionServerWatcher(ZooKeeperWatcher watcher) {
super(watcher);
}
/**
* Called when a new node has been created.
* @param path full path of the new node
*/
public void nodeCreated(String path) {
refreshListIfRightPath(path);
}
/**
* Called when a node has been deleted
* @param path full path of the deleted node
*/
public void nodeDeleted(String path) {
if (stopper.isStopped()) {
return;
}
boolean cont = refreshListIfRightPath(path);
if (!cont) {
return;
}
LOG.info(path + " znode expired, triggering replicatorRemoved event");
for (ReplicationListener rl : listeners) {
rl.regionServerRemoved(getZNodeName(path));
}
}
/**
* Called when an existing node has a child node added or removed.
* @param path full path of the node whose children have changed
*/
public void nodeChildrenChanged(String path) {
if (stopper.isStopped()) {
return;
}
refreshListIfRightPath(path);
}
private boolean refreshListIfRightPath(String path) {
if (!path.startsWith(this.watcher.znodePaths.rsZNode)) {
return false;
}
return refreshOtherRegionServersList();
}
}
/**
* Watcher used to follow the creation and deletion of peer clusters.
*/
public class PeersWatcher extends ZooKeeperListener {
/**
* Construct a ZooKeeper event listener.
*/
public PeersWatcher(ZooKeeperWatcher watcher) {
super(watcher);
}
/**
* Called when a node has been deleted
* @param path full path of the deleted node
*/
public void nodeDeleted(String path) {
List<String> peers = refreshPeersList(path);
if (peers == null) {
return;
}
if (isPeerPath(path)) {
String id = getZNodeName(path);
LOG.info(path + " znode expired, triggering peerRemoved event");
for (ReplicationListener rl : listeners) {
rl.peerRemoved(id);
}
}
}
/**
* Called when an existing node has a child node added or removed.
* @param path full path of the node whose children have changed
*/
public void nodeChildrenChanged(String path) {
List<String> peers = refreshPeersList(path);
if (peers == null) {
return;
}
LOG.info(path + " znode expired, triggering peerListChanged event");
for (ReplicationListener rl : listeners) {
rl.peerListChanged(peers);
}
}
}
/**
* Verify if this event is meant for us, and if so then get the latest peers' list from ZK. Also
* reset the watches.
* @param path path to check against
* @return A list of peers' identifiers if the event concerns this watcher, else null.
*/
private List<String> refreshPeersList(String path) {
if (!path.startsWith(getPeersZNode())) {
return null;
}
return this.replicationPeers.getAllPeerIds();
}
private String getPeersZNode() {
return this.peersZNode;
}
/**
* Extracts the znode name of a peer cluster from a ZK path
* @param fullPath Path to extract the id from
* @return the id or an empty string if path is invalid
*/
private String getZNodeName(String fullPath) {
String[] parts = fullPath.split("/");
return parts.length > 0 ? parts[parts.length - 1] : "";
}
/**
* Reads the list of region servers from ZK and atomically clears our local view of it and
* replaces it with the updated list.
* @return true if the local list of the other region servers was updated with the ZK data (even
* if it was empty), false if the data was missing in ZK
*/
private boolean refreshOtherRegionServersList() {
List<String> newRsList = getRegisteredRegionServers();
if (newRsList == null) {
return false;
} else {
synchronized (otherRegionServers) {
otherRegionServers.clear();
otherRegionServers.addAll(newRsList);
}
}
return true;
}
/**
* Get a list of all the other region servers in this cluster and set a watch
* @return a list of server nanes
*/
private List<String> getRegisteredRegionServers() {
List<String> result = null;
try {
result = ZKUtil.listChildrenAndWatchThem(this.zookeeper, this.zookeeper.znodePaths.rsZNode);
} catch (KeeperException e) {
this.abortable.abort("Get list of registered region servers", e);
}
return result;
}
}