/**
*
* 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.zookeeper;
import java.io.Closeable;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.concurrent.CountDownLatch;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hbase.Abortable;
import org.apache.hadoop.hbase.HConstants;
import org.apache.hadoop.hbase.ZooKeeperConnectionException;
import org.apache.hadoop.hbase.util.Threads;
import org.apache.zookeeper.KeeperException;
import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.ZooDefs;
import org.apache.zookeeper.data.ACL;
/**
* Acts as the single ZooKeeper Watcher. One instance of this is instantiated
* for each Master, RegionServer, and client process.
*
* <p>This is the only class that implements {@link Watcher}. Other internal
* classes which need to be notified of ZooKeeper events must register with
* the local instance of this watcher via {@link #registerListener}.
*
* <p>This class also holds and manages the connection to ZooKeeper. Code to
* deal with connection related events and exceptions are handled here.
*/
@InterfaceAudience.Public
@InterfaceStability.Evolving
public class ZooKeeperWatcher implements Watcher, Abortable, Closeable {
private static final Log LOG = LogFactory.getLog(ZooKeeperWatcher.class);
// Identifier for this watcher (for logging only). It is made of the prefix
// passed on construction and the zookeeper sessionid.
private String identifier;
// zookeeper quorum
private String quorum;
// zookeeper connection
private RecoverableZooKeeper recoverableZooKeeper;
// abortable in case of zk failure
protected Abortable abortable;
// listeners to be notified
private final List<ZooKeeperListener> listeners =
new CopyOnWriteArrayList<ZooKeeperListener>();
// Used by ZKUtil:waitForZKConnectionIfAuthenticating to wait for SASL
// negotiation to complete
public CountDownLatch saslLatch = new CountDownLatch(1);
// node names
// base znode for this cluster
public String baseZNode;
// znode containing location of server hosting root region
public String rootServerZNode;
// znode containing ephemeral nodes of the regionservers
public String rsZNode;
// znode containing ephemeral nodes of the draining regionservers
public String drainingZNode;
// znode of currently active master
private String masterAddressZNode;
// znode of this master in backup master directory, if not the active master
public String backupMasterAddressesZNode;
// znode containing the current cluster state
public String clusterStateZNode;
// znode used for region transitioning and assignment
public String assignmentZNode;
// znode used for table disabling/enabling
public String tableZNode;
// znode containing the unique cluster ID
public String clusterIdZNode;
// znode used for log splitting work assignment
public String splitLogZNode;
// znode containing the state of the load balancer
public String balancerZNode;
// Certain ZooKeeper nodes need to be world-readable
public static final ArrayList<ACL> CREATOR_ALL_AND_WORLD_READABLE =
new ArrayList<ACL>() { {
add(new ACL(ZooDefs.Perms.READ,ZooDefs.Ids.ANYONE_ID_UNSAFE));
add(new ACL(ZooDefs.Perms.ALL,ZooDefs.Ids.AUTH_IDS));
}};
private final Configuration conf;
private final Exception constructorCaller;
/**
* Instantiate a ZooKeeper connection and watcher.
* @param descriptor Descriptive string that is added to zookeeper sessionid
* and used as identifier for this instance.
* @throws IOException
* @throws ZooKeeperConnectionException
*/
public ZooKeeperWatcher(Configuration conf, String descriptor,
Abortable abortable) throws ZooKeeperConnectionException, IOException {
this(conf, descriptor, abortable, false);
}
/**
* Instantiate a ZooKeeper connection and watcher.
* @param descriptor Descriptive string that is added to zookeeper sessionid
* and used as identifier for this instance.
* @throws IOException
* @throws ZooKeeperConnectionException
*/
public ZooKeeperWatcher(Configuration conf, String descriptor,
Abortable abortable, boolean canCreateBaseZNode)
throws IOException, ZooKeeperConnectionException {
this.conf = conf;
// Capture a stack trace now. Will print it out later if problem so we can
// distingush amongst the myriad ZKWs.
try {
throw new Exception("ZKW CONSTRUCTOR STACK TRACE FOR DEBUGGING");
} catch (Exception e) {
this.constructorCaller = e;
}
this.quorum = ZKConfig.getZKQuorumServersString(conf);
// Identifier will get the sessionid appended later below down when we
// handle the syncconnect event.
this.identifier = descriptor;
this.abortable = abortable;
setNodeNames(conf);
this.recoverableZooKeeper = ZKUtil.connect(conf, quorum, this, descriptor);
if (canCreateBaseZNode) {
createBaseZNodes();
}
}
private void createBaseZNodes() throws ZooKeeperConnectionException {
try {
// Create all the necessary "directories" of znodes
ZKUtil.createAndFailSilent(this, baseZNode);
ZKUtil.createAndFailSilent(this, assignmentZNode);
ZKUtil.createAndFailSilent(this, rsZNode);
ZKUtil.createAndFailSilent(this, drainingZNode);
ZKUtil.createAndFailSilent(this, tableZNode);
ZKUtil.createAndFailSilent(this, splitLogZNode);
ZKUtil.createAndFailSilent(this, backupMasterAddressesZNode);
} catch (KeeperException e) {
throw new ZooKeeperConnectionException(
prefix("Unexpected KeeperException creating base node"), e);
}
}
@Override
public String toString() {
return this.identifier;
}
/**
* Adds this instance's identifier as a prefix to the passed <code>str</code>
* @param str String to amend.
* @return A new string with this instance's identifier as prefix: e.g.
* if passed 'hello world', the returned string could be
*/
public String prefix(final String str) {
return this.toString() + " " + str;
}
/**
* Set the local variable node names using the specified configuration.
*/
private void setNodeNames(Configuration conf) {
baseZNode = conf.get(HConstants.ZOOKEEPER_ZNODE_PARENT,
HConstants.DEFAULT_ZOOKEEPER_ZNODE_PARENT);
rootServerZNode = ZKUtil.joinZNode(baseZNode,
conf.get("zookeeper.znode.rootserver", "root-region-server"));
rsZNode = ZKUtil.joinZNode(baseZNode,
conf.get("zookeeper.znode.rs", "rs"));
drainingZNode = ZKUtil.joinZNode(baseZNode,
conf.get("zookeeper.znode.draining.rs", "draining"));
masterAddressZNode = ZKUtil.joinZNode(baseZNode,
conf.get("zookeeper.znode.master", "master"));
backupMasterAddressesZNode = ZKUtil.joinZNode(baseZNode,
conf.get("zookeeper.znode.backup.masters", "backup-masters"));
clusterStateZNode = ZKUtil.joinZNode(baseZNode,
conf.get("zookeeper.znode.state", "shutdown"));
assignmentZNode = ZKUtil.joinZNode(baseZNode,
conf.get("zookeeper.znode.unassigned", "unassigned"));
tableZNode = ZKUtil.joinZNode(baseZNode,
conf.get("zookeeper.znode.tableEnableDisable", "table"));
clusterIdZNode = ZKUtil.joinZNode(baseZNode,
conf.get("zookeeper.znode.clusterId", "hbaseid"));
splitLogZNode = ZKUtil.joinZNode(baseZNode,
conf.get("zookeeper.znode.splitlog", HConstants.SPLIT_LOGDIR_NAME));
balancerZNode = ZKUtil.joinZNode(baseZNode,
conf.get("zookeeper.znode.balancer", "balancer"));
}
/**
* Register the specified listener to receive ZooKeeper events.
* @param listener
*/
public void registerListener(ZooKeeperListener listener) {
listeners.add(listener);
}
/**
* Register the specified listener to receive ZooKeeper events and add it as
* the first in the list of current listeners.
* @param listener
*/
public void registerListenerFirst(ZooKeeperListener listener) {
listeners.add(0, listener);
}
/**
* Get the connection to ZooKeeper.
* @return connection reference to zookeeper
*/
public RecoverableZooKeeper getRecoverableZooKeeper() {
return recoverableZooKeeper;
}
public void reconnectAfterExpiration() throws IOException, InterruptedException {
recoverableZooKeeper.reconnectAfterExpiration();
}
/**
* Get the quorum address of this instance.
* @return quorum string of this zookeeper connection instance
*/
public String getQuorum() {
return quorum;
}
/**
* Method called from ZooKeeper for events and connection status.
* <p>
* Valid events are passed along to listeners. Connection status changes
* are dealt with locally.
*/
@Override
public void process(WatchedEvent event) {
LOG.debug(prefix("Received ZooKeeper Event, " +
"type=" + event.getType() + ", " +
"state=" + event.getState() + ", " +
"path=" + event.getPath()));
switch(event.getType()) {
// If event type is NONE, this is a connection status change
case None: {
connectionEvent(event);
break;
}
// Otherwise pass along to the listeners
case NodeCreated: {
for(ZooKeeperListener listener : listeners) {
listener.nodeCreated(event.getPath());
}
break;
}
case NodeDeleted: {
for(ZooKeeperListener listener : listeners) {
listener.nodeDeleted(event.getPath());
}
break;
}
case NodeDataChanged: {
for(ZooKeeperListener listener : listeners) {
listener.nodeDataChanged(event.getPath());
}
break;
}
case NodeChildrenChanged: {
for(ZooKeeperListener listener : listeners) {
listener.nodeChildrenChanged(event.getPath());
}
break;
}
}
}
// Connection management
/**
* Called when there is a connection-related event via the Watcher callback.
* <p>
* If Disconnected or Expired, this should shutdown the cluster. But, since
* we send a KeeperException.SessionExpiredException along with the abort
* call, it's possible for the Abortable to catch it and try to create a new
* session with ZooKeeper. This is what the client does in HCM.
* <p>
* @param event
*/
private void connectionEvent(WatchedEvent event) {
switch(event.getState()) {
case SyncConnected:
// Now, this callback can be invoked before the this.zookeeper is set.
// Wait a little while.
long finished = System.currentTimeMillis() +
this.conf.getLong("hbase.zookeeper.watcher.sync.connected.wait", 2000);
while (System.currentTimeMillis() < finished) {
Threads.sleep(1);
if (this.recoverableZooKeeper != null) break;
}
if (this.recoverableZooKeeper == null) {
LOG.error("ZK is null on connection event -- see stack trace " +
"for the stack trace when constructor was called on this zkw",
this.constructorCaller);
throw new NullPointerException("ZK is null");
}
this.identifier = this.identifier + "-0x" +
Long.toHexString(this.recoverableZooKeeper.getSessionId());
// Update our identifier. Otherwise ignore.
LOG.debug(this.identifier + " connected");
break;
case SaslAuthenticated:
if (ZKUtil.isSecureZooKeeper(this.conf)) {
// We are authenticated, clients can proceed.
saslLatch.countDown();
}
break;
case AuthFailed:
if (ZKUtil.isSecureZooKeeper(this.conf)) {
// We could not be authenticated, but clients should proceed anyway.
// Only access to znodes that require SASL authentication will be
// denied. The client may never need to access them.
saslLatch.countDown();
}
break;
// Abort the server if Disconnected or Expired
case Disconnected:
LOG.debug(prefix("Received Disconnected from ZooKeeper, ignoring"));
break;
case Expired:
if (ZKUtil.isSecureZooKeeper(this.conf)) {
// We consider Expired equivalent to AuthFailed for this
// connection. Authentication is never going to complete. The
// client should proceed to do cleanup.
saslLatch.countDown();
}
String msg = prefix(this.identifier + " received expired from " +
"ZooKeeper, aborting");
// TODO: One thought is to add call to ZooKeeperListener so say,
// ZooKeeperNodeTracker can zero out its data values.
if (this.abortable != null) this.abortable.abort(msg,
new KeeperException.SessionExpiredException());
break;
case ConnectedReadOnly:
break;
default:
throw new IllegalStateException("Received event is not valid.");
}
}
/**
* Forces a synchronization of this ZooKeeper client connection.
* <p>
* Executing this method before running other methods will ensure that the
* subsequent operations are up-to-date and consistent as of the time that
* the sync is complete.
* <p>
* This is used for compareAndSwap type operations where we need to read the
* data of an existing node and delete or transition that node, utilizing the
* previously read version and data. We want to ensure that the version read
* is up-to-date from when we begin the operation.
*/
public void sync(String path) {
this.recoverableZooKeeper.sync(path, null, null);
}
/**
* Handles KeeperExceptions in client calls.
* <p>
* This may be temporary but for now this gives one place to deal with these.
* <p>
* TODO: Currently this method rethrows the exception to let the caller handle
* <p>
* @param ke
* @throws KeeperException
*/
public void keeperException(KeeperException ke)
throws KeeperException {
LOG.error(prefix("Received unexpected KeeperException, re-throwing exception"), ke);
throw ke;
}
/**
* Handles InterruptedExceptions in client calls.
* <p>
* This may be temporary but for now this gives one place to deal with these.
* <p>
* TODO: Currently, this method does nothing.
* Is this ever expected to happen? Do we abort or can we let it run?
* Maybe this should be logged as WARN? It shouldn't happen?
* <p>
* @param ie
*/
public void interruptedException(InterruptedException ie) {
LOG.debug(prefix("Received InterruptedException, doing nothing here"), ie);
// At least preserver interrupt.
Thread.currentThread().interrupt();
// no-op
}
/**
* Close the connection to ZooKeeper.
*
* @throws InterruptedException
*/
public void close() {
try {
if (recoverableZooKeeper != null) {
recoverableZooKeeper.close();
}
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
}
}
public Configuration getConfiguration() {
return conf;
}
@Override
public void abort(String why, Throwable e) {
this.abortable.abort(why, e);
}
@Override
public boolean isAborted() {
return this.abortable.isAborted();
}
/**
* @return Path to the currently active master.
*/
public String getMasterAddressZNode() {
return this.masterAddressZNode;
}
}