Java tutorial
/** * * 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.master.snapshot; import java.io.IOException; import java.util.LinkedList; import java.util.List; import java.util.concurrent.CancellationException; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; import org.apache.hadoop.classification.InterfaceAudience; import org.apache.hadoop.fs.FileSystem; import org.apache.hadoop.fs.Path; import org.apache.hadoop.hbase.HRegionInfo; import org.apache.hadoop.hbase.HTableDescriptor; import org.apache.hadoop.hbase.TableName; import org.apache.hadoop.hbase.catalog.CatalogTracker; import org.apache.hadoop.hbase.catalog.MetaEditor; import org.apache.hadoop.hbase.errorhandling.ForeignException; import org.apache.hadoop.hbase.errorhandling.ForeignExceptionDispatcher; import org.apache.hadoop.hbase.executor.EventType; import org.apache.hadoop.hbase.master.AssignmentManager; import org.apache.hadoop.hbase.master.MasterFileSystem; import org.apache.hadoop.hbase.master.MasterServices; import org.apache.hadoop.hbase.master.MetricsSnapshot; import org.apache.hadoop.hbase.master.RegionStates; import org.apache.hadoop.hbase.master.SnapshotSentinel; import org.apache.hadoop.hbase.master.handler.TableEventHandler; import org.apache.hadoop.hbase.monitoring.MonitoredTask; import org.apache.hadoop.hbase.monitoring.TaskMonitor; import org.apache.hadoop.hbase.protobuf.generated.HBaseProtos.SnapshotDescription; import org.apache.hadoop.hbase.snapshot.ClientSnapshotDescriptionUtils; import org.apache.hadoop.hbase.snapshot.RestoreSnapshotException; import org.apache.hadoop.hbase.snapshot.RestoreSnapshotHelper; import org.apache.hadoop.hbase.snapshot.SnapshotDescriptionUtils; import org.apache.hadoop.hbase.snapshot.SnapshotManifest; /** * Handler to Restore a snapshot. * * <p>Uses {@link RestoreSnapshotHelper} to replace the table content with the * data available in the snapshot. */ @InterfaceAudience.Private public class RestoreSnapshotHandler extends TableEventHandler implements SnapshotSentinel { private static final Log LOG = LogFactory.getLog(RestoreSnapshotHandler.class); private final HTableDescriptor hTableDescriptor; private final SnapshotDescription snapshot; private final ForeignExceptionDispatcher monitor; private final MetricsSnapshot metricsSnapshot = new MetricsSnapshot(); private final MonitoredTask status; private volatile boolean stopped = false; public RestoreSnapshotHandler(final MasterServices masterServices, final SnapshotDescription snapshot, final HTableDescriptor htd) throws IOException { super(EventType.C_M_RESTORE_SNAPSHOT, htd.getTableName(), masterServices, masterServices); // Snapshot information this.snapshot = snapshot; // Monitor this.monitor = new ForeignExceptionDispatcher(); // Check table exists. getTableDescriptor(); // This is the new schema we are going to write out as this modification. this.hTableDescriptor = htd; this.status = TaskMonitor.get().createStatus( "Restoring snapshot '" + snapshot.getName() + "' to table " + hTableDescriptor.getTableName()); } @Override public RestoreSnapshotHandler prepare() throws IOException { return (RestoreSnapshotHandler) super.prepare(); } /** * The restore table is executed in place. * - The on-disk data will be restored - reference files are put in place without moving data * - [if something fail here: you need to delete the table and re-run the restore] * - hbase:meta will be updated * - [if something fail here: you need to run hbck to fix hbase:meta entries] * The passed in list gets changed in this method */ @Override protected void handleTableOperation(List<HRegionInfo> hris) throws IOException { MasterFileSystem fileSystemManager = masterServices.getMasterFileSystem(); CatalogTracker catalogTracker = masterServices.getCatalogTracker(); FileSystem fs = fileSystemManager.getFileSystem(); Path rootDir = fileSystemManager.getRootDir(); TableName tableName = hTableDescriptor.getTableName(); try { // 1. Update descriptor this.masterServices.getTableDescriptors().add(hTableDescriptor); // 2. Execute the on-disk Restore LOG.debug("Starting restore snapshot=" + ClientSnapshotDescriptionUtils.toString(snapshot)); Path snapshotDir = SnapshotDescriptionUtils.getCompletedSnapshotDir(snapshot, rootDir); SnapshotManifest manifest = SnapshotManifest.open(masterServices.getConfiguration(), fs, snapshotDir, snapshot); RestoreSnapshotHelper restoreHelper = new RestoreSnapshotHelper(masterServices.getConfiguration(), fs, manifest, this.hTableDescriptor, rootDir, monitor, status); RestoreSnapshotHelper.RestoreMetaChanges metaChanges = restoreHelper.restoreHdfsRegions(); // 3. Forces all the RegionStates to be offline // // The AssignmentManager keeps all the region states around // with no possibility to remove them, until the master is restarted. // This means that a region marked as SPLIT before the restore will never be assigned again. // To avoid having all states around all the regions are switched to the OFFLINE state, // which is the same state that the regions will be after a delete table. forceRegionsOffline(metaChanges); // 4. Applies changes to hbase:meta status.setStatus("Preparing to restore each region"); // 4.1 Removes the current set of regions from META // // By removing also the regions to restore (the ones present both in the snapshot // and in the current state) we ensure that no extra fields are present in META // e.g. with a simple add addRegionToMeta() the splitA and splitB attributes // not overwritten/removed, so you end up with old informations // that are not correct after the restore. List<HRegionInfo> hrisToRemove = new LinkedList<HRegionInfo>(); if (metaChanges.hasRegionsToRemove()) hrisToRemove.addAll(metaChanges.getRegionsToRemove()); MetaEditor.deleteRegions(catalogTracker, hrisToRemove); // 4.2 Add the new set of regions to META // // At this point the old regions are no longer present in META. // and the set of regions present in the snapshot will be written to META. // All the information in hbase:meta are coming from the .regioninfo of each region present // in the snapshot folder. hris.clear(); if (metaChanges.hasRegionsToAdd()) hris.addAll(metaChanges.getRegionsToAdd()); MetaEditor.addRegionsToMeta(catalogTracker, hris); if (metaChanges.hasRegionsToRestore()) { MetaEditor.overwriteRegions(catalogTracker, metaChanges.getRegionsToRestore()); } metaChanges.updateMetaParentRegions(catalogTracker, hris); // At this point the restore is complete. Next step is enabling the table. LOG.info("Restore snapshot=" + ClientSnapshotDescriptionUtils.toString(snapshot) + " on table=" + tableName + " completed!"); } catch (IOException e) { String msg = "restore snapshot=" + ClientSnapshotDescriptionUtils.toString(snapshot) + " failed. Try re-running the restore command."; LOG.error(msg, e); monitor.receive(new ForeignException(masterServices.getServerName().toString(), e)); throw new RestoreSnapshotException(msg, e); } } private void forceRegionsOffline(final RestoreSnapshotHelper.RestoreMetaChanges metaChanges) { forceRegionsOffline(metaChanges.getRegionsToAdd()); forceRegionsOffline(metaChanges.getRegionsToRestore()); forceRegionsOffline(metaChanges.getRegionsToRemove()); } private void forceRegionsOffline(final List<HRegionInfo> hris) { AssignmentManager am = this.masterServices.getAssignmentManager(); RegionStates states = am.getRegionStates(); if (hris != null) { for (HRegionInfo hri : hris) { states.regionOffline(hri); } } } @Override protected void completed(final Throwable exception) { this.stopped = true; if (exception != null) { status.abort("Restore snapshot '" + snapshot.getName() + "' failed because " + exception.getMessage()); } else { status.markComplete("Restore snapshot '" + snapshot.getName() + "'!"); } metricsSnapshot.addSnapshotRestore(status.getCompletionTimestamp() - status.getStartTime()); super.completed(exception); } @Override public boolean isFinished() { return this.stopped; } @Override public long getCompletionTimestamp() { return this.status.getCompletionTimestamp(); } @Override public SnapshotDescription getSnapshot() { return snapshot; } @Override public void cancel(String why) { if (this.stopped) return; this.stopped = true; String msg = "Stopping restore snapshot=" + ClientSnapshotDescriptionUtils.toString(snapshot) + " because: " + why; LOG.info(msg); CancellationException ce = new CancellationException(why); this.monitor.receive(new ForeignException(masterServices.getServerName().toString(), ce)); } @Override public ForeignException getExceptionIfFailed() { return this.monitor.getException(); } @Override public void rethrowExceptionIfFailed() throws ForeignException { monitor.rethrowException(); } }