/**
* 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;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collection;
import java.util.List;
import java.util.Map;
import java.util.SortedMap;
import java.util.SortedSet;
import java.util.TreeMap;
import java.util.TreeSet;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.hdfs.protocol.FSConstants;
/**
* LeaseManager does the lease housekeeping for writing on files.
* This class also provides useful static methods for lease recovery.
*
* Lease Recovery Algorithm
* 1) Namenode retrieves lease information
* 2) For each file f in the lease, consider the last block b of f
* 2.1) Get the datanodes which contains b
* 2.2) Assign one of the datanodes as the primary datanode p
* 2.3) p obtains a new generation stamp form the namenode
* 2.4) p get the block info from each datanode
* 2.5) p computes the minimum block length
* 2.6) p updates the datanodes, which have a valid generation stamp,
* with the new generation stamp and the minimum block length
* 2.7) p acknowledges the namenode the update results
* 2.8) Namenode updates the BlockInfo
* 2.9) Namenode removes f from the lease
* and removes the lease once all files have been removed
* 2.10) Namenode commit changes to edit log
*/
public class LeaseManager {
public static final Log LOG = LogFactory.getLog(LeaseManager.class);
private final FSNamesystem fsnamesystem;
private long softLimit = FSConstants.LEASE_SOFTLIMIT_PERIOD;
private long hardLimit = FSConstants.LEASE_HARDLIMIT_PERIOD;
//
// Used for handling lock-leases
// Mapping: leaseHolder -> Lease
//
private SortedMap<String, Lease> leases = new TreeMap<String, Lease>();
// Set of: Lease
private SortedSet<Lease> sortedLeases = new TreeSet<Lease>();
//
// Map path names to leases. It is protected by the sortedLeases lock.
// The map stores pathnames in lexicographical order.
//
private SortedMap<String, Lease> sortedLeasesByPath = new TreeMap<String, Lease>();
LeaseManager(FSNamesystem fsnamesystem) {this.fsnamesystem = fsnamesystem;}
Lease getLease(String holder) {
return leases.get(holder);
}
SortedSet<Lease> getSortedLeases() {return sortedLeases;}
/** @return the lease containing src */
public Lease getLeaseByPath(String src) {return sortedLeasesByPath.get(src);}
/** @return the number of leases currently in the system */
public synchronized int countLease() {return sortedLeases.size();}
/** @return the number of paths contained in all leases */
synchronized int countPath() {
int count = 0;
for(Lease lease : sortedLeases) {
count += lease.getPaths().size();
}
return count;
}
/**
* Adds (or re-adds) the lease for the specified file.
*/
synchronized Lease addLease(String holder, String src) {
Lease lease = getLease(holder);
if (lease == null) {
lease = new Lease(holder);
leases.put(holder, lease);
sortedLeases.add(lease);
} else {
renewLease(lease);
}
sortedLeasesByPath.put(src, lease);
lease.paths.add(src);
return lease;
}
/**
* Remove the specified lease and src.
*/
synchronized void removeLease(Lease lease, String src) {
sortedLeasesByPath.remove(src);
if (!lease.removePath(src)) {
LOG.error(src + " not found in lease.paths (=" + lease.paths + ")");
}
if (!lease.hasPath()) {
leases.remove(lease.holder);
if (!sortedLeases.remove(lease)) {
LOG.error(lease + " not found in sortedLeases");
}
}
}
/**
* Reassign lease for file src to the new holder.
*/
synchronized Lease reassignLease(Lease lease, String src, String newHolder) {
assert newHolder != null : "new lease holder is null";
if (lease != null) {
removeLease(lease, src);
}
return addLease(newHolder, src);
}
/**
* Remove the lease for the specified holder and src
*/
synchronized void removeLease(String holder, String src) {
Lease lease = getLease(holder);
if (lease != null) {
removeLease(lease, src);
}
}
/**
* Finds the pathname for the specified pendingFile
*/
synchronized String findPath(INodeFileUnderConstruction pendingFile
) throws IOException {
Lease lease = getLease(pendingFile.clientName);
if (lease != null) {
String src = lease.findPath(pendingFile);
if (src != null) {
return src;
}
}
throw new IOException("pendingFile (=" + pendingFile + ") not found."
+ "(lease=" + lease + ")");
}
/**
* Renew the lease(s) held by the given client
*/
synchronized void renewLease(String holder) {
renewLease(getLease(holder));
}
synchronized void renewLease(Lease lease) {
if (lease != null) {
sortedLeases.remove(lease);
lease.renew();
sortedLeases.add(lease);
}
}
/************************************************************
* A Lease governs all the locks held by a single client.
* For each client there's a corresponding lease, whose
* timestamp is updated when the client periodically
* checks in. If the client dies and allows its lease to
* expire, all the corresponding locks can be released.
*************************************************************/
class Lease implements Comparable<Lease> {
private final String holder;
private long lastUpdate;
private final Collection<String> paths = new TreeSet<String>();
/** Only LeaseManager object can create a lease */
private Lease(String holder) {
this.holder = holder;
renew();
}
/** Get the holder of the lease */
public String getHolder() {
return holder;
}
/** Only LeaseManager object can renew a lease */
private void renew() {
this.lastUpdate = FSNamesystem.now();
}
/** @return true if the Hard Limit Timer has expired */
public boolean expiredHardLimit() {
return FSNamesystem.now() - lastUpdate > hardLimit;
}
/** @return true if the Soft Limit Timer has expired */
public boolean expiredSoftLimit() {
return FSNamesystem.now() - lastUpdate > softLimit;
}
/**
* @return the path associated with the pendingFile and null if not found.
*/
private String findPath(INodeFileUnderConstruction pendingFile) {
for(String src : paths) {
if (fsnamesystem.dir.getFileINode(src) == pendingFile) {
return src;
}
}
return null;
}
/** Does this lease contain any path? */
boolean hasPath() {return !paths.isEmpty();}
boolean removePath(String src) {
return paths.remove(src);
}
/** {@inheritDoc} */
public String toString() {
return "[Lease. Holder: " + holder
+ ", pendingcreates: " + paths.size() + "]";
}
/** {@inheritDoc} */
public int compareTo(Lease o) {
Lease l1 = this;
Lease l2 = o;
long lu1 = l1.lastUpdate;
long lu2 = l2.lastUpdate;
if (lu1 < lu2) {
return -1;
} else if (lu1 > lu2) {
return 1;
} else {
return l1.holder.compareTo(l2.holder);
}
}
/** {@inheritDoc} */
public boolean equals(Object o) {
if (!(o instanceof Lease)) {
return false;
}
Lease obj = (Lease) o;
if (lastUpdate == obj.lastUpdate &&
holder.equals(obj.holder)) {
return true;
}
return false;
}
/** {@inheritDoc} */
public int hashCode() {
return holder.hashCode();
}
Collection<String> getPaths() {
return paths;
}
void replacePath(String oldpath, String newpath) {
paths.remove(oldpath);
paths.add(newpath);
}
}
synchronized void changeLease(String src, String dst,
String overwrite, String replaceBy) {
if (LOG.isDebugEnabled()) {
LOG.debug(getClass().getSimpleName() + ".changelease: " +
" src=" + src + ", dest=" + dst +
", overwrite=" + overwrite +
", replaceBy=" + replaceBy);
}
final int len = overwrite.length();
for(Map.Entry<String, Lease> entry : findLeaseWithPrefixPath(src, sortedLeasesByPath)) {
final String oldpath = entry.getKey();
final Lease lease = entry.getValue();
//overwrite must be a prefix of oldpath
final String newpath = replaceBy + oldpath.substring(len);
if (LOG.isDebugEnabled()) {
LOG.debug("changeLease: replacing " + oldpath + " with " + newpath);
}
lease.replacePath(oldpath, newpath);
sortedLeasesByPath.remove(oldpath);
sortedLeasesByPath.put(newpath, lease);
}
}
synchronized void removeLeaseWithPrefixPath(String prefix) {
for(Map.Entry<String, Lease> entry : findLeaseWithPrefixPath(prefix, sortedLeasesByPath)) {
if (LOG.isDebugEnabled()) {
LOG.debug(LeaseManager.class.getSimpleName()
+ ".removeLeaseWithPrefixPath: entry=" + entry);
}
removeLease(entry.getValue(), entry.getKey());
}
}
static private List<Map.Entry<String, Lease>> findLeaseWithPrefixPath(
String prefix, SortedMap<String, Lease> path2lease) {
if (LOG.isDebugEnabled()) {
LOG.debug(LeaseManager.class.getSimpleName() + ".findLease: prefix=" + prefix);
}
List<Map.Entry<String, Lease>> entries = new ArrayList<Map.Entry<String, Lease>>();
final int srclen = prefix.length();
for(Map.Entry<String, Lease> entry : path2lease.tailMap(prefix).entrySet()) {
final String p = entry.getKey();
if (!p.startsWith(prefix)) {
return entries;
}
if (p.length() == srclen || p.charAt(srclen) == Path.SEPARATOR_CHAR) {
entries.add(entry);
}
}
return entries;
}
public void setLeasePeriod(long softLimit, long hardLimit) {
this.softLimit = softLimit;
this.hardLimit = hardLimit;
}
/******************************************************
* Monitor checks for leases that have expired,
* and disposes of them.
******************************************************/
class Monitor implements Runnable {
final String name = getClass().getSimpleName();
/** Check leases periodically. */
public void run() {
for(; fsnamesystem.isRunning(); ) {
synchronized(fsnamesystem) {
checkLeases();
}
try {
Thread.sleep(2000);
} catch(InterruptedException ie) {
if (LOG.isDebugEnabled()) {
LOG.debug(name + " is interrupted", ie);
}
}
}
}
}
/** Check the leases beginning from the oldest. */
synchronized void checkLeases() {
for(; sortedLeases.size() > 0; ) {
final Lease oldest = sortedLeases.first();
if (!oldest.expiredHardLimit()) {
return;
}
LOG.info("Lease " + oldest + " has expired hard limit");
final List<String> removing = new ArrayList<String>();
// need to create a copy of the oldest lease paths, becuase
// internalReleaseLease() removes paths corresponding to empty files,
// i.e. it needs to modify the collection being iterated over
// causing ConcurrentModificationException
String[] leasePaths = new String[oldest.getPaths().size()];
oldest.getPaths().toArray(leasePaths);
for(String p : leasePaths) {
try {
fsnamesystem.internalReleaseLeaseOne(oldest, p);
} catch (IOException e) {
LOG.error("Cannot release the path "+p+" in the lease "+oldest, e);
removing.add(p);
}
}
for(String p : removing) {
removeLease(oldest, p);
}
}
}
/** {@inheritDoc} */
public synchronized String toString() {
return getClass().getSimpleName() + "= {"
+ "\n leases=" + leases
+ "\n sortedLeases=" + sortedLeases
+ "\n sortedLeasesByPath=" + sortedLeasesByPath
+ "\n}";
}
}