/*
* Copyright The Apache Software Foundation
*
* 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.coprocessor.example;
import java.io.IOException;
import java.util.Collections;
import java.util.List;
import java.util.NavigableSet;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.hbase.CoprocessorEnvironment;
import org.apache.hadoop.hbase.HConstants;
import org.apache.hadoop.hbase.client.IsolationLevel;
import org.apache.hadoop.hbase.client.Scan;
import org.apache.hadoop.hbase.coprocessor.BaseRegionObserver;
import org.apache.hadoop.hbase.coprocessor.ObserverContext;
import org.apache.hadoop.hbase.coprocessor.RegionCoprocessorEnvironment;
import org.apache.hadoop.hbase.coprocessor.RegionObserver;
import org.apache.hadoop.hbase.regionserver.HStore;
import org.apache.hadoop.hbase.regionserver.Store;
import org.apache.hadoop.hbase.regionserver.ScanInfo;
import org.apache.hadoop.hbase.regionserver.InternalScanner;
import org.apache.hadoop.hbase.regionserver.KeyValueScanner;
import org.apache.hadoop.hbase.regionserver.ScanType;
import org.apache.hadoop.hbase.regionserver.Store;
import org.apache.hadoop.hbase.regionserver.StoreScanner;
import org.apache.hadoop.hbase.util.Bytes;
import org.apache.hadoop.hbase.util.EnvironmentEdgeManager;
import org.apache.hadoop.hbase.zookeeper.ZooKeeperWatcher;
import org.apache.zookeeper.KeeperException;
import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.ZooKeeper;
/**
* This is an example showing how a RegionObserver could configured
* via ZooKeeper in order to control a Region compaction, flush, and scan policy.
*
* This also demonstrated the use of shared {@link RegionObserver} state.
* See {@link RegionCoprocessorEnvironment#getSharedData()}.
*
* This would be useful for an incremental backup tool, which would indicate the last
* time of a successful backup via ZK and instruct HBase to not delete data that was
* inserted since (based on wall clock time).
*
* This implements org.apache.zookeeper.Watcher directly instead of using
* {@link ZooKeeperWatcher}, because RegionObservers come and go and currently
* listeners registered with ZooKeeperWatcher cannot be removed.
*/
public class ZooKeeperScanPolicyObserver extends BaseRegionObserver {
public static final String node = "/backup/example/lastbackup";
public static final String zkkey = "ZK";
private static final Log LOG = LogFactory.getLog(ZooKeeperScanPolicyObserver.class);
/**
* Internal watcher that keep "data" up to date asynchronously.
*/
private static class ZKWatcher implements Watcher {
private byte[] data = null;
private ZooKeeper zk;
private volatile boolean needSetup = true;
private volatile long lastSetupTry = 0;
public ZKWatcher(ZooKeeper zk) {
this.zk = zk;
// trigger the listening
getData();
}
/**
* Get the maintained data. In case of any ZK exceptions this will retry
* establishing the connection (but not more than twice/minute).
*
* getData is on the critical path, so make sure it is fast unless there is
* a problem (network partion, ZK ensemble down, etc)
* Make sure at most one (unlucky) thread retries and other threads don't pile up
* while that threads tries to recreate the connection.
*
* @return the last know version of the data
*/
@edu.umd.cs.findbugs.annotations.SuppressWarnings(value="REC_CATCH_EXCEPTION")
public byte[] getData() {
// try at most twice/minute
if (needSetup && EnvironmentEdgeManager.currentTimeMillis() > lastSetupTry + 30000) {
synchronized (this) {
// make sure only one thread tries to reconnect
if (needSetup) {
needSetup = false;
} else {
return data;
}
}
// do this without the lock held to avoid threads piling up on this lock,
// as it can take a while
try {
LOG.debug("Connecting to ZK");
// record this attempt
lastSetupTry = EnvironmentEdgeManager.currentTimeMillis();
if (zk.exists(node, false) != null) {
data = zk.getData(node, this, null);
LOG.debug("Read synchronously: "+(data == null ? "null" : Bytes.toLong(data)));
} else {
zk.exists(node, this);
}
} catch (Exception x) {
// try again if this fails
needSetup = true;
}
}
return data;
}
@Override
public void process(WatchedEvent event) {
switch(event.getType()) {
case NodeDataChanged:
case NodeCreated:
try {
// get data and re-watch
data = zk.getData(node, this, null);
LOG.debug("Read asynchronously: "+(data == null ? "null" : Bytes.toLong(data)));
} catch (InterruptedException ix) {
} catch (KeeperException kx) {
needSetup = true;
}
break;
case NodeDeleted:
try {
// just re-watch
zk.exists(node, this);
data = null;
} catch (InterruptedException ix) {
} catch (KeeperException kx) {
needSetup = true;
}
break;
default:
// ignore
}
}
}
@Override
public void start(CoprocessorEnvironment e) throws IOException {
RegionCoprocessorEnvironment re = (RegionCoprocessorEnvironment) e;
if (!re.getSharedData().containsKey(zkkey)) {
// there is a short race here
// in the worst case we create a watcher that will be notified once
re.getSharedData().putIfAbsent(
zkkey,
new ZKWatcher(re.getRegionServerServices().getZooKeeper()
.getRecoverableZooKeeper().getZooKeeper()));
}
}
@Override
public void stop(CoprocessorEnvironment e) throws IOException {
// nothing to do here
}
protected ScanInfo getScanInfo(Store store, RegionCoprocessorEnvironment e) {
byte[] data = ((ZKWatcher)e.getSharedData().get(zkkey)).getData();
if (data == null) {
return null;
}
ScanInfo oldSI = store.getScanInfo();
if (oldSI.getTtl() == Long.MAX_VALUE) {
return null;
}
long ttl = Math.max(EnvironmentEdgeManager.currentTimeMillis() -
Bytes.toLong(data), oldSI.getTtl());
return new ScanInfo(store.getFamily(), ttl,
oldSI.getTimeToPurgeDeletes(), oldSI.getComparator());
}
@Override
public InternalScanner preFlushScannerOpen(final ObserverContext<RegionCoprocessorEnvironment> c,
Store store, KeyValueScanner memstoreScanner, InternalScanner s) throws IOException {
ScanInfo scanInfo = getScanInfo(store, c.getEnvironment());
if (scanInfo == null) {
// take default action
return null;
}
Scan scan = new Scan();
scan.setMaxVersions(scanInfo.getMaxVersions());
return new StoreScanner(store, scanInfo, scan, Collections.singletonList(memstoreScanner),
ScanType.COMPACT_RETAIN_DELETES, store.getSmallestReadPoint(), HConstants.OLDEST_TIMESTAMP);
}
@Override
public InternalScanner preCompactScannerOpen(
final ObserverContext<RegionCoprocessorEnvironment> c,
Store store, List<? extends KeyValueScanner> scanners, ScanType scanType, long earliestPutTs,
InternalScanner s) throws IOException {
ScanInfo scanInfo = getScanInfo(store, c.getEnvironment());
if (scanInfo == null) {
// take default action
return null;
}
Scan scan = new Scan();
scan.setMaxVersions(scanInfo.getMaxVersions());
return new StoreScanner(store, scanInfo, scan, scanners, scanType,
store.getSmallestReadPoint(), earliestPutTs);
}
@Override
public KeyValueScanner preStoreScannerOpen(final ObserverContext<RegionCoprocessorEnvironment> c,
final Store store, final Scan scan, final NavigableSet<byte[]> targetCols,
final KeyValueScanner s) throws IOException {
ScanInfo scanInfo = getScanInfo(store, c.getEnvironment());
if (scanInfo == null) {
// take default action
return null;
}
return new StoreScanner(store, scanInfo, scan, targetCols,
((HStore)store).getHRegion().getReadpoint(IsolationLevel.READ_COMMITTED));
}
}