/**
* 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.DataInput;
import java.io.DataOutput;
import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.Comparator;
import java.util.Date;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.hdfs.DFSUtil;
import org.apache.hadoop.hdfs.protocol.HdfsConstants;
import org.apache.hadoop.hdfs.server.namenode.FSImageFormat;
import org.apache.hadoop.hdfs.server.namenode.FSImageSerialization;
import org.apache.hadoop.hdfs.server.namenode.INode;
import org.apache.hadoop.hdfs.server.namenode.INodeDirectory;
import org.apache.hadoop.hdfs.util.ReadOnlyList;
/** Snapshot of a sub-tree in the namesystem. */
@InterfaceAudience.Private
public class Snapshot implements Comparable<byte[]> {
public static final int INVALID_ID = -1;
/**
* The pattern for generating the default snapshot name.
* E.g. s20130412-151029.033
*/
private static final String DEFAULT_SNAPSHOT_NAME_PATTERN = "'s'yyyyMMdd-HHmmss.SSS";
public static String generateDefaultSnapshotName() {
return new SimpleDateFormat(DEFAULT_SNAPSHOT_NAME_PATTERN).format(new Date());
}
public static String getSnapshotPath(String snapshottableDir,
String snapshotRelativePath) {
final StringBuilder b = new StringBuilder(snapshottableDir);
if (b.charAt(b.length() - 1) != Path.SEPARATOR_CHAR) {
b.append(Path.SEPARATOR);
}
return b.append(HdfsConstants.DOT_SNAPSHOT_DIR)
.append(Path.SEPARATOR)
.append(snapshotRelativePath)
.toString();
}
/**
* Get the name of the given snapshot.
* @param s The given snapshot.
* @return The name of the snapshot, or an empty string if {@code s} is null
*/
static String getSnapshotName(Snapshot s) {
return s != null ? s.getRoot().getLocalName() : "";
}
/**
* Compare snapshot with IDs, where null indicates the current status thus
* is greater than any non-null snapshot.
*/
public static final Comparator<Snapshot> ID_COMPARATOR
= new Comparator<Snapshot>() {
@Override
public int compare(Snapshot left, Snapshot right) {
return ID_INTEGER_COMPARATOR.compare(
left == null? null: left.getId(),
right == null? null: right.getId());
}
};
/**
* Compare snapshot with IDs, where null indicates the current status thus
* is greater than any non-null ID.
*/
public static final Comparator<Integer> ID_INTEGER_COMPARATOR
= new Comparator<Integer>() {
@Override
public int compare(Integer left, Integer right) {
// null means the current state, thus should be the largest
if (left == null) {
return right == null? 0: 1;
} else {
return right == null? -1: left - right;
}
}
};
/**
* Find the latest snapshot that 1) covers the given inode (which means the
* snapshot was either taken on the inode or taken on an ancestor of the
* inode), and 2) was taken before the given snapshot (if the given snapshot
* is not null).
*
* @param inode the given inode that the returned snapshot needs to cover
* @param anchor the returned snapshot should be taken before this snapshot.
* @return the latest snapshot covers the given inode and was taken before the
* the given snapshot (if it is not null).
*/
public static Snapshot findLatestSnapshot(INode inode, Snapshot anchor) {
Snapshot latest = null;
for(; inode != null; inode = inode.getParent()) {
if (inode.isDirectory()) {
final INodeDirectory dir = inode.asDirectory();
if (dir instanceof INodeDirectoryWithSnapshot) {
latest = ((INodeDirectoryWithSnapshot) dir).getDiffs().updatePrior(
anchor, latest);
}
}
}
return latest;
}
static Snapshot read(DataInput in, FSImageFormat.Loader loader)
throws IOException {
final int snapshotId = in.readInt();
final INode root = loader.loadINodeWithLocalName(false, in, false);
return new Snapshot(snapshotId, root.asDirectory(), null);
}
/** The root directory of the snapshot. */
static public class Root extends INodeDirectory {
Root(INodeDirectory other) {
super(other, false);
}
@Override
public ReadOnlyList<INode> getChildrenList(Snapshot snapshot) {
return getParent().getChildrenList(snapshot);
}
@Override
public INode getChild(byte[] name, Snapshot snapshot) {
return getParent().getChild(name, snapshot);
}
@Override
public String getFullPathName() {
return getSnapshotPath(getParent().getFullPathName(), getLocalName());
}
}
/** Snapshot ID. */
private final int id;
/** The root directory of the snapshot. */
private final Root root;
Snapshot(int id, String name, INodeDirectorySnapshottable dir) {
this(id, dir, dir);
this.root.setLocalName(DFSUtil.string2Bytes(name));
}
Snapshot(int id, INodeDirectory dir, INodeDirectorySnapshottable parent) {
this.id = id;
this.root = new Root(dir);
this.root.setParent(parent);
}
public int getId() {
return id;
}
/** @return the root directory of the snapshot. */
public Root getRoot() {
return root;
}
@Override
public int compareTo(byte[] bytes) {
return root.compareTo(bytes);
}
@Override
public boolean equals(Object that) {
if (this == that) {
return true;
} else if (that == null || !(that instanceof Snapshot)) {
return false;
}
return this.id == ((Snapshot)that).id;
}
@Override
public int hashCode() {
return id;
}
@Override
public String toString() {
return getClass().getSimpleName() + "." + root.getLocalName() + "(id=" + id + ")";
}
/** Serialize the fields to out */
void write(DataOutput out) throws IOException {
out.writeInt(id);
// write root
FSImageSerialization.writeINodeDirectory(root, out);
}
}