/*
*
* 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.io.Closeable;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.atomic.AtomicBoolean;
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.hbase.Abortable;
import org.apache.hadoop.hbase.ServerName;
import org.apache.hadoop.hbase.exceptions.DeserializationException;
import org.apache.hadoop.hbase.protobuf.ProtobufUtil;
import org.apache.hadoop.hbase.protobuf.generated.ZooKeeperProtos;
import org.apache.hadoop.hbase.zookeeper.ZKUtil;
import org.apache.hadoop.hbase.zookeeper.ZooKeeperNodeTracker;
import org.apache.hadoop.hbase.zookeeper.ZooKeeperWatcher;
import org.apache.zookeeper.KeeperException;
import org.apache.zookeeper.KeeperException.NodeExistsException;
import com.google.protobuf.InvalidProtocolBufferException;
/**
* This class acts as a wrapper for all the objects used to identify and
* communicate with remote peers and is responsible for answering to expired
* sessions and re-establishing the ZK connections.
*/
@InterfaceAudience.Private
public class ReplicationPeer implements Abortable, Closeable {
private static final Log LOG = LogFactory.getLog(ReplicationPeer.class);
private final String clusterKey;
private final String id;
private List<ServerName> regionServers = new ArrayList<ServerName>(0);
private final AtomicBoolean peerEnabled = new AtomicBoolean();
// Cannot be final since a new object needs to be recreated when session fails
private ZooKeeperWatcher zkw;
private final Configuration conf;
private long lastRegionserverUpdate;
private PeerStateTracker peerStateTracker;
/**
* Constructor that takes all the objects required to communicate with the
* specified peer, except for the region server addresses.
* @param conf configuration object to this peer
* @param key cluster key used to locate the peer
* @param id string representation of this peer's identifier
*/
public ReplicationPeer(Configuration conf, String key, String id) throws ReplicationException {
this.conf = conf;
this.clusterKey = key;
this.id = id;
try {
this.reloadZkWatcher();
} catch (IOException e) {
throw new ReplicationException("Error connecting to peer cluster with peerId=" + id, e);
}
}
/**
* start a state tracker to check whether this peer is enabled or not
*
* @param zookeeper zk watcher for the local cluster
* @param peerStateNode path to zk node which stores peer state
* @throws KeeperException
*/
public void startStateTracker(ZooKeeperWatcher zookeeper, String peerStateNode)
throws KeeperException {
ensurePeerEnabled(zookeeper, peerStateNode);
this.peerStateTracker = new PeerStateTracker(peerStateNode, zookeeper, this);
this.peerStateTracker.start();
try {
this.readPeerStateZnode();
} catch (DeserializationException e) {
throw ZKUtil.convert(e);
}
}
private void readPeerStateZnode() throws DeserializationException {
this.peerEnabled.set(isStateEnabled(this.peerStateTracker.getData(false)));
}
/**
* Get the cluster key of that peer
* @return string consisting of zk ensemble addresses, client port
* and root znode
*/
public String getClusterKey() {
return clusterKey;
}
/**
* Get the state of this peer
* @return atomic boolean that holds the status
*/
public AtomicBoolean getPeerEnabled() {
return peerEnabled;
}
/**
* Get a list of all the addresses of all the region servers
* for this peer cluster
* @return list of addresses
*/
public List<ServerName> getRegionServers() {
return regionServers;
}
/**
* Set the list of region servers for that peer
* @param regionServers list of addresses for the region servers
*/
public void setRegionServers(List<ServerName> regionServers) {
this.regionServers = regionServers;
lastRegionserverUpdate = System.currentTimeMillis();
}
/**
* Get the ZK connection to this peer
* @return zk connection
*/
public ZooKeeperWatcher getZkw() {
return zkw;
}
/**
* Get the timestamp at which the last change occurred to the list of region servers to replicate
* to.
* @return The System.currentTimeMillis at the last time the list of peer region servers changed.
*/
public long getLastRegionserverUpdate() {
return lastRegionserverUpdate;
}
/**
* Get the identifier of this peer
* @return string representation of the id (short)
*/
public String getId() {
return id;
}
/**
* Get the configuration object required to communicate with this peer
* @return configuration object
*/
public Configuration getConfiguration() {
return conf;
}
@Override
public void abort(String why, Throwable e) {
LOG.fatal("The ReplicationPeer coresponding to peer " + clusterKey
+ " was aborted for the following reason(s):" + why, e);
}
/**
* Closes the current ZKW (if not null) and creates a new one
* @throws IOException If anything goes wrong connecting
*/
public void reloadZkWatcher() throws IOException {
if (zkw != null) zkw.close();
zkw = new ZooKeeperWatcher(conf,
"connection to cluster: " + id, this);
}
@Override
public boolean isAborted() {
// Currently the replication peer is never "Aborted", we just log when the
// abort method is called.
return false;
}
@Override
public void close() throws IOException {
if (zkw != null){
zkw.close();
}
}
/**
* Parse the raw data from ZK to get a peer's state
* @param bytes raw ZK data
* @return True if the passed in <code>bytes</code> are those of a pb serialized ENABLED state.
* @throws DeserializationException
*/
public static boolean isStateEnabled(final byte[] bytes) throws DeserializationException {
ZooKeeperProtos.ReplicationState.State state = parseStateFrom(bytes);
return ZooKeeperProtos.ReplicationState.State.ENABLED == state;
}
/**
* @param bytes Content of a state znode.
* @return State parsed from the passed bytes.
* @throws DeserializationException
*/
private static ZooKeeperProtos.ReplicationState.State parseStateFrom(final byte[] bytes)
throws DeserializationException {
ProtobufUtil.expectPBMagicPrefix(bytes);
int pblen = ProtobufUtil.lengthOfPBMagic();
ZooKeeperProtos.ReplicationState.Builder builder =
ZooKeeperProtos.ReplicationState.newBuilder();
ZooKeeperProtos.ReplicationState state;
try {
state = builder.mergeFrom(bytes, pblen, bytes.length - pblen).build();
return state.getState();
} catch (InvalidProtocolBufferException e) {
throw new DeserializationException(e);
}
}
/**
* Utility method to ensure an ENABLED znode is in place; if not present, we create it.
* @param zookeeper
* @param path Path to znode to check
* @return True if we created the znode.
* @throws NodeExistsException
* @throws KeeperException
*/
private static boolean ensurePeerEnabled(final ZooKeeperWatcher zookeeper, final String path)
throws NodeExistsException, KeeperException {
if (ZKUtil.checkExists(zookeeper, path) == -1) {
// There is a race b/w PeerWatcher and ReplicationZookeeper#add method to create the
// peer-state znode. This happens while adding a peer.
// The peer state data is set as "ENABLED" by default.
ZKUtil.createNodeIfNotExistsAndWatch(zookeeper, path,
ReplicationStateZKBase.ENABLED_ZNODE_BYTES);
return true;
}
return false;
}
/**
* Tracker for state of this peer
*/
public class PeerStateTracker extends ZooKeeperNodeTracker {
public PeerStateTracker(String peerStateZNode, ZooKeeperWatcher watcher,
Abortable abortable) {
super(watcher, peerStateZNode, abortable);
}
@Override
public synchronized void nodeDataChanged(String path) {
if (path.equals(node)) {
super.nodeDataChanged(path);
try {
readPeerStateZnode();
} catch (DeserializationException e) {
LOG.warn("Failed deserializing the content of " + path, e);
}
}
}
}
}