/**
* 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.hdfs.server.namenode.snapshot;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import org.apache.hadoop.HadoopIllegalArgumentException;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.hdfs.DFSUtil;
import org.apache.hadoop.hdfs.protocol.QuotaExceededException;
import org.apache.hadoop.hdfs.protocol.SnapshotException;
import org.apache.hadoop.hdfs.server.blockmanagement.BlockStoragePolicySuite;
import org.apache.hadoop.hdfs.server.namenode.Content;
import org.apache.hadoop.hdfs.server.namenode.ContentSummaryComputationContext;
import org.apache.hadoop.hdfs.server.namenode.INode;
import org.apache.hadoop.hdfs.server.namenode.INodeDirectory;
import org.apache.hadoop.hdfs.server.namenode.INodeDirectory.SnapshotAndINode;
import org.apache.hadoop.hdfs.server.namenode.INodeFile;
import org.apache.hadoop.hdfs.server.namenode.INodeReference;
import org.apache.hadoop.hdfs.server.namenode.INodeReference.WithCount;
import org.apache.hadoop.hdfs.server.namenode.INodeReference.WithName;
import org.apache.hadoop.hdfs.util.Diff.ListType;
import org.apache.hadoop.hdfs.util.ReadOnlyList;
import org.apache.hadoop.util.Time;
import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Preconditions;
import com.google.common.collect.Lists;
/**
* A directory with this feature is a snapshottable directory, where snapshots
* can be taken. This feature extends {@link DirectoryWithSnapshotFeature}, and
* maintains extra information about all the snapshots taken on this directory.
*/
@InterfaceAudience.Private
public class DirectorySnapshottableFeature extends DirectoryWithSnapshotFeature {
/** Limit the number of snapshot per snapshottable directory. */
static final int SNAPSHOT_LIMIT = 1 << 16;
/**
* Snapshots of this directory in ascending order of snapshot names.
* Note that snapshots in ascending order of snapshot id are stored in
* {@link DirectoryWithSnapshotFeature}.diffs (a private field).
*/
private final List<Snapshot> snapshotsByNames = new ArrayList<Snapshot>();
/** Number of snapshots allowed. */
private int snapshotQuota = SNAPSHOT_LIMIT;
public DirectorySnapshottableFeature(DirectoryWithSnapshotFeature feature) {
super(feature == null ? null : feature.getDiffs());
}
/** @return the number of existing snapshots. */
public int getNumSnapshots() {
return snapshotsByNames.size();
}
private int searchSnapshot(byte[] snapshotName) {
return Collections.binarySearch(snapshotsByNames, snapshotName);
}
/** @return the snapshot with the given name. */
public Snapshot getSnapshot(byte[] snapshotName) {
final int i = searchSnapshot(snapshotName);
return i < 0? null: snapshotsByNames.get(i);
}
public Snapshot getSnapshotById(int sid) {
for (Snapshot s : snapshotsByNames) {
if (s.getId() == sid) {
return s;
}
}
return null;
}
/** @return {@link #snapshotsByNames} as a {@link ReadOnlyList} */
public ReadOnlyList<Snapshot> getSnapshotList() {
return ReadOnlyList.Util.asReadOnlyList(snapshotsByNames);
}
/**
* Rename a snapshot
* @param path
* The directory path where the snapshot was taken. Used for
* generating exception message.
* @param oldName
* Old name of the snapshot
* @param newName
* New name the snapshot will be renamed to
* @throws SnapshotException
* Throw SnapshotException when either the snapshot with the old
* name does not exist or a snapshot with the new name already
* exists
*/
public void renameSnapshot(String path, String oldName, String newName)
throws SnapshotException {
if (newName.equals(oldName)) {
return;
}
final int indexOfOld = searchSnapshot(DFSUtil.string2Bytes(oldName));
if (indexOfOld < 0) {
throw new SnapshotException("The snapshot " + oldName
+ " does not exist for directory " + path);
} else {
final byte[] newNameBytes = DFSUtil.string2Bytes(newName);
int indexOfNew = searchSnapshot(newNameBytes);
if (indexOfNew >= 0) {
throw new SnapshotException("The snapshot " + newName
+ " already exists for directory " + path);
}
// remove the one with old name from snapshotsByNames
Snapshot snapshot = snapshotsByNames.remove(indexOfOld);
final INodeDirectory ssRoot = snapshot.getRoot();
ssRoot.setLocalName(newNameBytes);
indexOfNew = -indexOfNew - 1;
if (indexOfNew <= indexOfOld) {
snapshotsByNames.add(indexOfNew, snapshot);
} else { // indexOfNew > indexOfOld
snapshotsByNames.add(indexOfNew - 1, snapshot);
}
}
}
public int getSnapshotQuota() {
return snapshotQuota;
}
public void setSnapshotQuota(int snapshotQuota) {
if (snapshotQuota < 0) {
throw new HadoopIllegalArgumentException(
"Cannot set snapshot quota to " + snapshotQuota + " < 0");
}
this.snapshotQuota = snapshotQuota;
}
/**
* Simply add a snapshot into the {@link #snapshotsByNames}. Used when loading
* fsimage.
*/
void addSnapshot(Snapshot snapshot) {
this.snapshotsByNames.add(snapshot);
}
/** Add a snapshot. */
public Snapshot addSnapshot(INodeDirectory snapshotRoot, int id, String name)
throws SnapshotException, QuotaExceededException {
//check snapshot quota
final int n = getNumSnapshots();
if (n + 1 > snapshotQuota) {
throw new SnapshotException("Failed to add snapshot: there are already "
+ n + " snapshot(s) and the snapshot quota is "
+ snapshotQuota);
}
final Snapshot s = new Snapshot(id, name, snapshotRoot);
final byte[] nameBytes = s.getRoot().getLocalNameBytes();
final int i = searchSnapshot(nameBytes);
if (i >= 0) {
throw new SnapshotException("Failed to add snapshot: there is already a "
+ "snapshot with the same name \"" + Snapshot.getSnapshotName(s) + "\".");
}
final DirectoryDiff d = getDiffs().addDiff(id, snapshotRoot);
d.setSnapshotRoot(s.getRoot());
snapshotsByNames.add(-i - 1, s);
// set modification time
final long now = Time.now();
snapshotRoot.updateModificationTime(now, Snapshot.CURRENT_STATE_ID);
s.getRoot().setModificationTime(now, Snapshot.CURRENT_STATE_ID);
return s;
}
/**
* Remove the snapshot with the given name from {@link #snapshotsByNames},
* and delete all the corresponding DirectoryDiff.
*
* @param reclaimContext records blocks and inodes that need to be reclaimed
* @param snapshotRoot The directory where we take snapshots
* @param snapshotName The name of the snapshot to be removed
* @return The removed snapshot. Null if no snapshot with the given name
* exists.
*/
public Snapshot removeSnapshot(
INode.ReclaimContext reclaimContext, INodeDirectory snapshotRoot,
String snapshotName) throws SnapshotException {
final int i = searchSnapshot(DFSUtil.string2Bytes(snapshotName));
if (i < 0) {
throw new SnapshotException("Cannot delete snapshot " + snapshotName
+ " from path " + snapshotRoot.getFullPathName()
+ ": the snapshot does not exist.");
} else {
final Snapshot snapshot = snapshotsByNames.get(i);
int prior = Snapshot.findLatestSnapshot(snapshotRoot, snapshot.getId());
snapshotRoot.cleanSubtree(reclaimContext, snapshot.getId(), prior);
// remove from snapshotsByNames after successfully cleaning the subtree
snapshotsByNames.remove(i);
return snapshot;
}
}
public ContentSummaryComputationContext computeContentSummary(
final BlockStoragePolicySuite bsps,
final INodeDirectory snapshotRoot,
final ContentSummaryComputationContext summary) {
snapshotRoot.computeContentSummary(summary);
summary.getCounts().addContent(Content.SNAPSHOT, snapshotsByNames.size());
summary.getCounts().addContent(Content.SNAPSHOTTABLE_DIRECTORY, 1);
return summary;
}
/**
* Compute the difference between two snapshots (or a snapshot and the current
* directory) of the directory.
*
* @param from The name of the start point of the comparison. Null indicating
* the current tree.
* @param to The name of the end point. Null indicating the current tree.
* @return The difference between the start/end points.
* @throws SnapshotException If there is no snapshot matching the starting
* point, or if endSnapshotName is not null but cannot be identified
* as a previous snapshot.
*/
SnapshotDiffInfo computeDiff(final INodeDirectory snapshotRoot,
final String from, final String to) throws SnapshotException {
Snapshot fromSnapshot = getSnapshotByName(snapshotRoot, from);
Snapshot toSnapshot = getSnapshotByName(snapshotRoot, to);
// if the start point is equal to the end point, return null
if (from.equals(to)) {
return null;
}
SnapshotDiffInfo diffs = new SnapshotDiffInfo(snapshotRoot, fromSnapshot,
toSnapshot);
computeDiffRecursively(snapshotRoot, snapshotRoot, new ArrayList<byte[]>(),
diffs);
return diffs;
}
/**
* Find the snapshot matching the given name.
*
* @param snapshotRoot The directory where snapshots were taken.
* @param snapshotName The name of the snapshot.
* @return The corresponding snapshot. Null if snapshotName is null or empty.
* @throws SnapshotException If snapshotName is not null or empty, but there
* is no snapshot matching the name.
*/
private Snapshot getSnapshotByName(INodeDirectory snapshotRoot,
String snapshotName) throws SnapshotException {
Snapshot s = null;
if (snapshotName != null && !snapshotName.isEmpty()) {
final int index = searchSnapshot(DFSUtil.string2Bytes(snapshotName));
if (index < 0) {
throw new SnapshotException("Cannot find the snapshot of directory "
+ snapshotRoot.getFullPathName() + " with name " + snapshotName);
}
s = snapshotsByNames.get(index);
}
return s;
}
/**
* Recursively compute the difference between snapshots under a given
* directory/file.
* @param snapshotRoot The directory where snapshots were taken.
* @param node The directory/file under which the diff is computed.
* @param parentPath Relative path (corresponding to the snapshot root) of
* the node's parent.
* @param diffReport data structure used to store the diff.
*/
private void computeDiffRecursively(final INodeDirectory snapshotRoot,
INode node, List<byte[]> parentPath, SnapshotDiffInfo diffReport) {
final Snapshot earlierSnapshot = diffReport.isFromEarlier() ?
diffReport.getFrom() : diffReport.getTo();
final Snapshot laterSnapshot = diffReport.isFromEarlier() ?
diffReport.getTo() : diffReport.getFrom();
byte[][] relativePath = parentPath.toArray(new byte[parentPath.size()][]);
if (node.isDirectory()) {
final ChildrenDiff diff = new ChildrenDiff();
INodeDirectory dir = node.asDirectory();
DirectoryWithSnapshotFeature sf = dir.getDirectoryWithSnapshotFeature();
if (sf != null) {
boolean change = sf.computeDiffBetweenSnapshots(earlierSnapshot,
laterSnapshot, diff, dir);
if (change) {
diffReport.addDirDiff(dir, relativePath, diff);
}
}
ReadOnlyList<INode> children = dir.getChildrenList(earlierSnapshot
.getId());
for (INode child : children) {
final byte[] name = child.getLocalNameBytes();
boolean toProcess = diff.searchIndex(ListType.DELETED, name) < 0;
if (!toProcess && child instanceof INodeReference.WithName) {
byte[][] renameTargetPath = findRenameTargetPath(
snapshotRoot, (WithName) child,
laterSnapshot == null ? Snapshot.CURRENT_STATE_ID :
laterSnapshot.getId());
if (renameTargetPath != null) {
toProcess = true;
diffReport.setRenameTarget(child.getId(), renameTargetPath);
}
}
if (toProcess) {
parentPath.add(name);
computeDiffRecursively(snapshotRoot, child, parentPath, diffReport);
parentPath.remove(parentPath.size() - 1);
}
}
} else if (node.isFile() && node.asFile().isWithSnapshot()) {
INodeFile file = node.asFile();
boolean change = file.getFileWithSnapshotFeature()
.changedBetweenSnapshots(file, earlierSnapshot, laterSnapshot);
if (change) {
diffReport.addFileDiff(file, relativePath);
}
}
}
/**
* We just found a deleted WithName node as the source of a rename operation.
* However, we should include it in our snapshot diff report as rename only
* if the rename target is also under the same snapshottable directory.
*/
private byte[][] findRenameTargetPath(final INodeDirectory snapshotRoot,
INodeReference.WithName wn, final int snapshotId) {
INode inode = wn.getReferredINode();
final LinkedList<byte[]> ancestors = Lists.newLinkedList();
while (inode != null) {
if (inode == snapshotRoot) {
return ancestors.toArray(new byte[ancestors.size()][]);
}
if (inode instanceof INodeReference.WithCount) {
inode = ((WithCount) inode).getParentRef(snapshotId);
} else {
INode parent = inode.getParentReference() != null ? inode
.getParentReference() : inode.getParent();
if (parent != null && parent instanceof INodeDirectory) {
int sid = parent.asDirectory().searchChild(inode);
if (sid < snapshotId) {
return null;
}
}
if (!(parent instanceof WithCount)) {
ancestors.addFirst(inode.getLocalNameBytes());
}
inode = parent;
}
}
return null;
}
@Override
public String toString() {
return "snapshotsByNames=" + snapshotsByNames;
}
@VisibleForTesting
public void dumpTreeRecursively(INodeDirectory snapshotRoot, PrintWriter out,
StringBuilder prefix, int snapshot) {
if (snapshot == Snapshot.CURRENT_STATE_ID) {
out.println();
out.print(prefix);
out.print("Snapshot of ");
final String name = snapshotRoot.getLocalName();
out.print(name.isEmpty()? "/": name);
out.print(": quota=");
out.print(getSnapshotQuota());
int n = 0;
for(DirectoryDiff diff : getDiffs()) {
if (diff.isSnapshotRoot()) {
n++;
}
}
Preconditions.checkState(n == snapshotsByNames.size(), "#n=" + n
+ ", snapshotsByNames.size()=" + snapshotsByNames.size());
out.print(", #snapshot=");
out.println(n);
INodeDirectory.dumpTreeRecursively(out, prefix,
new Iterable<SnapshotAndINode>() {
@Override
public Iterator<SnapshotAndINode> iterator() {
return new Iterator<SnapshotAndINode>() {
final Iterator<DirectoryDiff> i = getDiffs().iterator();
private DirectoryDiff next = findNext();
private DirectoryDiff findNext() {
for(; i.hasNext(); ) {
final DirectoryDiff diff = i.next();
if (diff.isSnapshotRoot()) {
return diff;
}
}
return null;
}
@Override
public boolean hasNext() {
return next != null;
}
@Override
public SnapshotAndINode next() {
final SnapshotAndINode pair = new SnapshotAndINode(next
.getSnapshotId(), getSnapshotById(next.getSnapshotId())
.getRoot());
next = findNext();
return pair;
}
@Override
public void remove() {
throw new UnsupportedOperationException();
}
};
}
});
}
}
}