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/**
* 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.regionserver.snapshot;
import java.io.IOException;
import java.util.List;
import java.util.concurrent.Callable;
import org.apache.yetus.audience.InterfaceAudience;
import org.apache.yetus.audience.InterfaceStability;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.apache.hadoop.hbase.client.IsolationLevel;
import org.apache.hadoop.hbase.errorhandling.ForeignException;
import org.apache.hadoop.hbase.errorhandling.ForeignExceptionDispatcher;
import org.apache.hadoop.hbase.procedure.ProcedureMember;
import org.apache.hadoop.hbase.procedure.Subprocedure;
import org.apache.hadoop.hbase.regionserver.HRegion;
import org.apache.hadoop.hbase.regionserver.HRegion.FlushResult;
import org.apache.hadoop.hbase.regionserver.Region.Operation;
import org.apache.hadoop.hbase.regionserver.snapshot.RegionServerSnapshotManager.SnapshotSubprocedurePool;
import org.apache.hadoop.hbase.shaded.protobuf.generated.SnapshotProtos.SnapshotDescription;
import org.apache.hadoop.hbase.snapshot.ClientSnapshotDescriptionUtils;
/**
* This online snapshot implementation uses the distributed procedure framework to force a
* store flush and then records the hfiles. Its enter stage does nothing. Its leave stage then
* flushes the memstore, builds the region server's snapshot manifest from its hfiles list, and
* copies .regioninfos into the snapshot working directory. At the master side, there is an atomic
* rename of the working dir into the proper snapshot directory.
*/
@InterfaceAudience.Private
@InterfaceStability.Unstable
public class FlushSnapshotSubprocedure extends Subprocedure {
private static final Logger LOG = LoggerFactory.getLogger(FlushSnapshotSubprocedure.class);
private final List regions;
private final SnapshotDescription snapshot;
private final SnapshotSubprocedurePool taskManager;
private boolean snapshotSkipFlush = false;
// the maximum number of attempts we flush
final static int MAX_RETRIES = 3;
public FlushSnapshotSubprocedure(ProcedureMember member,
ForeignExceptionDispatcher errorListener, long wakeFrequency, long timeout,
List regions, SnapshotDescription snapshot,
SnapshotSubprocedurePool taskManager) {
super(member, snapshot.getName(), errorListener, wakeFrequency, timeout);
this.snapshot = snapshot;
if (this.snapshot.getType() == SnapshotDescription.Type.SKIPFLUSH) {
snapshotSkipFlush = true;
}
this.regions = regions;
this.taskManager = taskManager;
}
/**
* Callable for adding files to snapshot manifest working dir. Ready for multithreading.
*/
public static class RegionSnapshotTask implements Callable {
private HRegion region;
private boolean skipFlush;
private ForeignExceptionDispatcher monitor;
private SnapshotDescription snapshotDesc;
public RegionSnapshotTask(HRegion region, SnapshotDescription snapshotDesc,
boolean skipFlush, ForeignExceptionDispatcher monitor) {
this.region = region;
this.skipFlush = skipFlush;
this.monitor = monitor;
this.snapshotDesc = snapshotDesc;
}
@Override
public Void call() throws Exception {
// Taking the region read lock prevents the individual region from being closed while a
// snapshot is in progress. This is helpful but not sufficient for preventing races with
// snapshots that involve multiple regions and regionservers. It is still possible to have
// an interleaving such that globally regions are missing, so we still need the verification
// step.
LOG.debug("Starting snapshot operation on " + region);
region.startRegionOperation(Operation.SNAPSHOT);
try {
if (skipFlush) {
/*
* This is to take an online-snapshot without force a coordinated flush to prevent pause
* The snapshot type is defined inside the snapshot description. FlushSnapshotSubprocedure
* should be renamed to distributedSnapshotSubprocedure, and the flush() behavior can be
* turned on/off based on the flush type.
* To minimized the code change, class name is not changed.
*/
LOG.debug("take snapshot without flush memstore first");
} else {
LOG.debug("Flush Snapshotting region " + region.toString() + " started...");
boolean succeeded = false;
long readPt = region.getReadPoint(IsolationLevel.READ_COMMITTED);
for (int i = 0; i < MAX_RETRIES; i++) {
FlushResult res = region.flush(true);
if (res.getResult() == FlushResult.Result.CANNOT_FLUSH) {
// CANNOT_FLUSH may mean that a flush is already on-going
// we need to wait for that flush to complete
region.waitForFlushes();
if (region.getMaxFlushedSeqId() >= readPt) {
// writes at the start of the snapshot have been persisted
succeeded = true;
break;
}
} else {
succeeded = true;
break;
}
}
if (!succeeded) {
throw new IOException("Unable to complete flush after " + MAX_RETRIES + " attempts");
}
}
region.addRegionToSnapshot(snapshotDesc, monitor);
if (skipFlush) {
LOG.debug("... SkipFlush Snapshotting region " + region.toString() + " completed.");
} else {
LOG.debug("... Flush Snapshotting region " + region.toString() + " completed.");
}
} finally {
LOG.debug("Closing snapshot operation on " + region);
region.closeRegionOperation(Operation.SNAPSHOT);
}
return null;
}
}
private void flushSnapshot() throws ForeignException {
if (regions.isEmpty()) {
// No regions on this RS, we are basically done.
return;
}
monitor.rethrowException();
// assert that the taskManager is empty.
if (taskManager.hasTasks()) {
throw new IllegalStateException("Attempting to take snapshot "
+ ClientSnapshotDescriptionUtils.toString(snapshot)
+ " but we currently have outstanding tasks");
}
// Add all hfiles already existing in region.
for (HRegion region : regions) {
// submit one task per region for parallelize by region.
taskManager.submitTask(new RegionSnapshotTask(region, snapshot, snapshotSkipFlush, monitor));
monitor.rethrowException();
}
// wait for everything to complete.
LOG.debug("Flush Snapshot Tasks submitted for " + regions.size() + " regions");
try {
taskManager.waitForOutstandingTasks();
} catch (InterruptedException e) {
LOG.error("got interrupted exception for " + getMemberName());
throw new ForeignException(getMemberName(), e);
}
}
/**
* do nothing, core of snapshot is executed in {@link #insideBarrier} step.
*/
@Override
public void acquireBarrier() throws ForeignException {
// NO OP
}
/**
* do a flush snapshot of every region on this rs from the target table.
*/
@Override
public byte[] insideBarrier() throws ForeignException {
flushSnapshot();
return new byte[0];
}
/**
* Cancel threads if they haven't finished.
*/
@Override
public void cleanup(Exception e) {
LOG.info("Aborting all online FLUSH snapshot subprocedure task threads for '"
+ snapshot.getName() + "' due to error", e);
try {
taskManager.cancelTasks();
} catch (InterruptedException e1) {
Thread.currentThread().interrupt();
}
}
/**
* Hooray!
*/
public void releaseBarrier() {
// NO OP
}
}
