/**
* 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.zookeeper.server.persistence;
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.nio.ByteBuffer;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.zip.Adler32;
import java.util.zip.CheckedInputStream;
import java.util.zip.CheckedOutputStream;
import org.apache.jute.BinaryInputArchive;
import org.apache.jute.BinaryOutputArchive;
import org.apache.jute.InputArchive;
import org.apache.jute.OutputArchive;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.apache.zookeeper.server.DataTree;
import org.apache.zookeeper.server.util.SerializeUtils;
/**
* This class implements the snapshot interface.
* it is responsible for storing, serializing
* and deserializing the right snapshot.
* and provides access to the snapshots.
*/
public class FileSnap implements SnapShot {
File snapDir;
private volatile boolean close = false;
private static final int VERSION=2;
private static final long dbId=-1;
private static final Logger LOG = LoggerFactory.getLogger(FileSnap.class);
public final static int SNAP_MAGIC
= ByteBuffer.wrap("ZKSN".getBytes()).getInt();
public FileSnap(File snapDir) {
this.snapDir = snapDir;
}
/**
* deserialize a data tree from the most recent snapshot
* @return the zxid of the snapshot
*/
public long deserialize(DataTree dt, Map<Long, Integer> sessions)
throws IOException {
// we run through 100 snapshots (not all of them)
// if we cannot get it running within 100 snapshots
// we should give up
List<File> snapList = findNValidSnapshots(100);
if (snapList.size() == 0) {
return -1L;
}
File snap = null;
boolean foundValid = false;
for (int i = 0; i < snapList.size(); i++) {
snap = snapList.get(i);
InputStream snapIS = null;
CheckedInputStream crcIn = null;
try {
LOG.info("Reading snapshot " + snap);
snapIS = new BufferedInputStream(new FileInputStream(snap));
crcIn = new CheckedInputStream(snapIS, new Adler32());
InputArchive ia = BinaryInputArchive.getArchive(crcIn);
deserialize(dt,sessions, ia);
long checkSum = crcIn.getChecksum().getValue();
long val = ia.readLong("val");
if (val != checkSum) {
throw new IOException("CRC corruption in snapshot : " + snap);
}
foundValid = true;
break;
} catch(IOException e) {
LOG.warn("problem reading snap file " + snap, e);
} finally {
if (snapIS != null)
snapIS.close();
if (crcIn != null)
crcIn.close();
}
}
if (!foundValid) {
throw new IOException("Not able to find valid snapshots in " + snapDir);
}
dt.lastProcessedZxid = Util.getZxidFromName(snap.getName(), "snapshot");
return dt.lastProcessedZxid;
}
/**
* deserialize the datatree from an inputarchive
* @param dt the datatree to be serialized into
* @param sessions the sessions to be filled up
* @param ia the input archive to restore from
* @throws IOException
*/
public void deserialize(DataTree dt, Map<Long, Integer> sessions,
InputArchive ia) throws IOException {
FileHeader header = new FileHeader();
header.deserialize(ia, "fileheader");
if (header.getMagic() != SNAP_MAGIC) {
throw new IOException("mismatching magic headers "
+ header.getMagic() +
" != " + FileSnap.SNAP_MAGIC);
}
SerializeUtils.deserializeSnapshot(dt,ia,sessions);
}
/**
* find the most recent snapshot in the database.
* @return the file containing the most recent snapshot
*/
public File findMostRecentSnapshot() throws IOException {
List<File> files = findNValidSnapshots(1);
if (files.size() == 0) {
return null;
}
return files.get(0);
}
/**
* find the last (maybe) valid n snapshots. this does some
* minor checks on the validity of the snapshots. It just
* checks for / at the end of the snapshot. This does
* not mean that the snapshot is truly valid but is
* valid with a high probability. also, the most recent
* will be first on the list.
* @param n the number of most recent snapshots
* @return the last n snapshots (the number might be
* less than n in case enough snapshots are not available).
* @throws IOException
*/
private List<File> findNValidSnapshots(int n) throws IOException {
List<File> files = Util.sortDataDir(snapDir.listFiles(),"snapshot", false);
int count = 0;
List<File> list = new ArrayList<File>();
for (File f : files) {
// we should catch the exceptions
// from the valid snapshot and continue
// until we find a valid one
try {
if (Util.isValidSnapshot(f)) {
list.add(f);
count++;
if (count == n) {
break;
}
}
} catch (IOException e) {
LOG.info("invalid snapshot " + f, e);
}
}
return list;
}
/**
* find the last n snapshots. this does not have
* any checks if the snapshot might be valid or not
* @param the number of most recent snapshots
* @return the last n snapshots
* @throws IOException
*/
public List<File> findNRecentSnapshots(int n) throws IOException {
List<File> files = Util.sortDataDir(snapDir.listFiles(), "snapshot", false);
int i = 0;
List<File> list = new ArrayList<File>();
for (File f: files) {
if (i==n)
break;
i++;
list.add(f);
}
return list;
}
/**
* serialize the datatree and sessions
* @param dt the datatree to be serialized
* @param sessions the sessions to be serialized
* @param oa the output archive to serialize into
* @param header the header of this snapshot
* @throws IOException
*/
protected void serialize(DataTree dt,Map<Long, Integer> sessions,
OutputArchive oa, FileHeader header) throws IOException {
// this is really a programmatic error and not something that can
// happen at runtime
if(header==null)
throw new IllegalStateException(
"Snapshot's not open for writing: uninitialized header");
header.serialize(oa, "fileheader");
SerializeUtils.serializeSnapshot(dt,oa,sessions);
}
/**
* serialize the datatree and session into the file snapshot
* @param dt the datatree to be serialized
* @param sessions the sessions to be serialized
* @param snapShot the file to store snapshot into
*/
public synchronized void serialize(DataTree dt, Map<Long, Integer> sessions, File snapShot)
throws IOException {
if (!close) {
OutputStream sessOS = new BufferedOutputStream(new FileOutputStream(snapShot));
CheckedOutputStream crcOut = new CheckedOutputStream(sessOS, new Adler32());
//CheckedOutputStream cout = new CheckedOutputStream()
OutputArchive oa = BinaryOutputArchive.getArchive(crcOut);
FileHeader header = new FileHeader(SNAP_MAGIC, VERSION, dbId);
serialize(dt,sessions,oa, header);
long val = crcOut.getChecksum().getValue();
oa.writeLong(val, "val");
oa.writeString("/", "path");
sessOS.flush();
crcOut.close();
sessOS.close();
}
}
/**
* synchronized close just so that if serialize is in place
* the close operation will block and will wait till serialize
* is done and will set the close flag
*/
@Override
public synchronized void close() throws IOException {
close = true;
}
}