PersistentManagerBase.java
/*
* 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.catalina.session;
import java.io.IOException;
import java.util.Arrays;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;
import org.apache.catalina.Lifecycle;
import org.apache.catalina.LifecycleException;
import org.apache.catalina.LifecycleState;
import org.apache.catalina.Session;
import org.apache.catalina.Store;
import org.apache.catalina.StoreManager;
import org.apache.juli.logging.Log;
import org.apache.juli.logging.LogFactory;
/**
* Extends the {@link ManagerBase} class to implement most of the functionality required by a Manager which supports any
* kind of persistence, even if only for restarts.
* <p>
* <b>IMPLEMENTATION NOTE</b>: Correct behavior of session storing and reloading depends upon external calls to the
* {@link Lifecycle#start()} and {@link Lifecycle#stop()} methods of this class at the correct times.
*
* @author Craig R. McClanahan
*/
public abstract class PersistentManagerBase extends ManagerBase implements StoreManager {
private final Log log = LogFactory.getLog(PersistentManagerBase.class); // must not be static
// ----------------------------------------------------- Instance Variables
/**
* The descriptive name of this Manager implementation (for logging).
*/
private static final String name = "PersistentManagerBase";
/**
* Key of the note of a session in which the timestamp of last backup is stored.
*/
private static final String PERSISTED_LAST_ACCESSED_TIME =
"org.apache.catalina.session.PersistentManagerBase.persistedLastAccessedTime";
/**
* Store object which will manage the Session store.
*/
protected Store store = null;
/**
* Whether to save and reload sessions when the Manager <code>unload</code> and <code>load</code> methods are
* called.
*/
protected boolean saveOnRestart = true;
/**
* How long a session must be idle before it should be backed up. {@code -1} means sessions won't be backed up.
*/
protected int maxIdleBackup = -1;
/**
* The minimum time in seconds a session must be idle before it is eligible to be swapped to disk to keep the active
* session count below maxActiveSessions. Setting to {@code -1} means sessions will not be swapped out to keep the
* active session count down.
*/
protected int minIdleSwap = -1;
/**
* The maximum time in seconds a session may be idle before it is eligible to be swapped to disk due to inactivity.
* Setting this to {@code -1} means sessions should not be swapped out just because of inactivity.
*/
protected int maxIdleSwap = -1;
/**
* Sessions currently being swapped in and the associated locks
*/
private final Map<String,Object> sessionSwapInLocks = new HashMap<>();
/*
* Session that is currently getting swapped in to prevent loading it more than once concurrently
*/
private final ThreadLocal<Session> sessionToSwapIn = new ThreadLocal<>();
// ------------------------------------------------------------- Properties
/**
* Indicates how many seconds old a session can get, after its last use in a request, before it should be backed up
* to the store. {@code -1} means sessions are not backed up.
*
* @return the timeout after which sessions are ripe for back up
*/
public int getMaxIdleBackup() {
return maxIdleBackup;
}
/**
* Sets the option to back sessions up to the Store after they are used in a request. Sessions remain available in
* memory after being backed up, so they are not passivated as they are when swapped out. The value set indicates
* how old a session may get (since its last use) before it must be backed up: {@code -1} means sessions are not
* backed up.
* <p>
* Note that this is not a hard limit: sessions are checked against this age limit periodically according to
* {@code processExpiresFrequency}. This value should be considered to indicate when a session is ripe for backing
* up.
* <p>
* So it is possible that a session may be idle for {@code maxIdleBackup +
* processExpiresFrequency * engine.backgroundProcessorDelay} seconds, plus the time it takes to handle other
* session expiration, swapping, etc. tasks.
*
* @param backup The number of seconds after their last accessed time when they should be written to the Store.
*/
public void setMaxIdleBackup(int backup) {
if (backup == this.maxIdleBackup) {
return;
}
int oldBackup = this.maxIdleBackup;
this.maxIdleBackup = backup;
support.firePropertyChange("maxIdleBackup", Integer.valueOf(oldBackup), Integer.valueOf(this.maxIdleBackup));
}
/**
* @return The maximum time in seconds a session may be idle before it is eligible to be swapped to disk due to
* inactivity. A value of {@code -1} means sessions should not be swapped out just because of
* inactivity.
*/
public int getMaxIdleSwap() {
return maxIdleSwap;
}
/**
* Sets the maximum time in seconds a session may be idle before it is eligible to be swapped to disk due to
* inactivity. Setting this to {@code -1} means sessions should not be swapped out just because of inactivity.
*
* @param max time in seconds to wait for possible swap out
*/
public void setMaxIdleSwap(int max) {
if (max == this.maxIdleSwap) {
return;
}
int oldMaxIdleSwap = this.maxIdleSwap;
this.maxIdleSwap = max;
support.firePropertyChange("maxIdleSwap", Integer.valueOf(oldMaxIdleSwap), Integer.valueOf(this.maxIdleSwap));
}
/**
* @return The minimum time in seconds a session must be idle before it is eligible to be swapped to disk to keep
* the active session count below maxActiveSessions. A value of {@code -1} means sessions will not be
* swapped out to keep the active session count down.
*/
public int getMinIdleSwap() {
return minIdleSwap;
}
/**
* Sets the minimum time in seconds a session must be idle before it is eligible to be swapped to disk to keep the
* active session count below maxActiveSessions. Setting to {@code -1} means sessions will not be swapped out to
* keep the active session count down.
*
* @param min time in seconds before a possible swap out
*/
public void setMinIdleSwap(int min) {
if (this.minIdleSwap == min) {
return;
}
int oldMinIdleSwap = this.minIdleSwap;
this.minIdleSwap = min;
support.firePropertyChange("minIdleSwap", Integer.valueOf(oldMinIdleSwap), Integer.valueOf(this.minIdleSwap));
}
/**
* Check, whether a session is loaded in memory
*
* @param id The session id for the session to be searched for
*
* @return {@code true}, if the session id is loaded in memory otherwise {@code false} is returned
*/
public boolean isLoaded(String id) {
try {
if (super.findSession(id) != null) {
return true;
}
} catch (IOException e) {
log.error(sm.getString("persistentManager.isLoadedError", id), e);
}
return false;
}
@Override
public String getName() {
return name;
}
/**
* Set the Store object which will manage persistent Session storage for this Manager.
*
* @param store the associated Store
*/
public void setStore(Store store) {
this.store = store;
store.setManager(this);
}
@Override
public Store getStore() {
return this.store;
}
/**
* Indicates whether sessions are saved when the Manager is shut down properly. This requires the {@link #unload()}
* method to be called.
*
* @return {@code true}, when sessions should be saved on restart, {code false} otherwise
*/
public boolean getSaveOnRestart() {
return saveOnRestart;
}
/**
* Set the option to save sessions to the Store when the Manager is shut down, then loaded when the Manager starts
* again. If set to false, any sessions found in the Store may still be picked up when the Manager is started again.
*
* @param saveOnRestart {@code true} if sessions should be saved on restart, {@code false} if they should be
* ignored.
*/
public void setSaveOnRestart(boolean saveOnRestart) {
if (saveOnRestart == this.saveOnRestart) {
return;
}
boolean oldSaveOnRestart = this.saveOnRestart;
this.saveOnRestart = saveOnRestart;
support.firePropertyChange("saveOnRestart", Boolean.valueOf(oldSaveOnRestart),
Boolean.valueOf(this.saveOnRestart));
}
// --------------------------------------------------------- Public Methods
/**
* Clear all sessions from the Store.
*/
public void clearStore() {
if (store == null) {
return;
}
try {
store.clear();
} catch (IOException e) {
log.error(sm.getString("persistentManager.storeClearError"), e);
}
}
/**
* {@inheritDoc}
* <p>
* Direct call to processExpires and processPersistenceChecks
*/
@Override
public void processExpires() {
long timeNow = System.currentTimeMillis();
Session sessions[] = findSessions();
int expireHere = 0;
if (log.isTraceEnabled()) {
log.trace("Start expire sessions " + getName() + " at " + timeNow + " sessioncount " + sessions.length);
}
for (Session session : sessions) {
if (!session.isValid()) {
expiredSessions.incrementAndGet();
expireHere++;
}
}
processPersistenceChecks();
if (getStore() instanceof StoreBase) {
((StoreBase) getStore()).processExpires();
}
long timeEnd = System.currentTimeMillis();
if (log.isTraceEnabled()) {
log.trace("End expire sessions " + getName() + " processingTime " + (timeEnd - timeNow) +
" expired sessions: " + expireHere);
}
processingTime += (timeEnd - timeNow);
}
/**
* Called by the background thread after active sessions have been checked for expiration, to allow sessions to be
* swapped out, backed up, etc.
*/
public void processPersistenceChecks() {
processMaxIdleSwaps();
processMaxActiveSwaps();
processMaxIdleBackups();
}
/**
* {@inheritDoc}
* <p>
* This method checks the persistence store if persistence is enabled, otherwise just uses the functionality from
* ManagerBase.
*/
@Override
public Session findSession(String id) throws IOException {
Session session = super.findSession(id);
// OK, at this point, we're not sure if another thread is trying to
// remove the session or not so the only way around this is to lock it
// (or attempt to) and then try to get it by this session id again. If
// the other code ran swapOut, then we should get a null back during
// this run, and if not, we lock it out so we can access the session
// safely.
if (session != null) {
synchronized (session) {
session = super.findSession(session.getIdInternal());
if (session != null) {
// To keep any external calling code from messing up the
// concurrency.
session.access();
session.endAccess();
}
}
}
if (session != null) {
return session;
}
// See if the Session is in the Store
session = swapIn(id);
return session;
}
@Override
public void removeSuper(Session session) {
super.remove(session, false);
}
/**
* Load all sessions found in the persistence mechanism, assuming they are marked as valid and have not passed their
* expiration limit. If persistence is not supported, this method returns without doing anything.
* <p>
* Note that by default, this method is not called by the MiddleManager class. In order to use it, a subclass must
* specifically call it, for example in the start() and/or processPersistenceChecks() methods.
*/
@Override
public void load() {
// Initialize our internal data structures
sessions.clear();
if (store == null) {
return;
}
String[] ids = null;
try {
ids = store.keys();
} catch (IOException e) {
log.error(sm.getString("persistentManager.storeLoadKeysError"), e);
return;
}
int n = ids.length;
if (n == 0) {
return;
}
if (log.isDebugEnabled()) {
log.debug(sm.getString("persistentManager.loading", String.valueOf(n)));
}
for (String id : ids) {
try {
swapIn(id);
} catch (IOException e) {
log.error(sm.getString("persistentManager.storeLoadError"), e);
}
}
}
/**
* {@inheritDoc}
* <p>
* Remove this Session from the Store.
*/
@Override
public void remove(Session session, boolean update) {
super.remove(session, update);
if (store != null) {
removeSession(session.getIdInternal());
}
}
/**
* Remove this Session from the active Sessions for this Manager, and from the Store.
*
* @param id Session's id to be removed
*/
protected void removeSession(String id) {
try {
store.remove(id);
} catch (IOException e) {
log.error(sm.getString("persistentManager.removeError"), e);
}
}
/**
* Save all currently active sessions in the appropriate persistence mechanism, if any. If persistence is not
* supported, this method returns without doing anything.
* <p>
* Note that by default, this method is not called by the MiddleManager class. In order to use it, a subclass must
* specifically call it, for example in the stop() and/or processPersistenceChecks() methods.
*/
@Override
public void unload() {
if (store == null) {
return;
}
Session sessions[] = findSessions();
int n = sessions.length;
if (n == 0) {
return;
}
if (log.isDebugEnabled()) {
log.debug(sm.getString("persistentManager.unloading", String.valueOf(n)));
}
for (Session session : sessions) {
try {
swapOut(session);
} catch (IOException e) {
// This is logged in writeSession()
}
}
}
@Override
public int getActiveSessionsFull() {
// In memory session count
int result = getActiveSessions();
try {
// Store session count
result += getStore().getSize();
} catch (IOException ioe) {
log.warn(sm.getString("persistentManager.storeSizeException"));
}
return result;
}
@Override
public Set<String> getSessionIdsFull() {
// In memory session ID list
Set<String> sessionIds = new HashSet<>(sessions.keySet());
try {
// Store session ID list
sessionIds.addAll(Arrays.asList(getStore().keys()));
} catch (IOException e) {
log.warn(sm.getString("persistentManager.storeKeysException"));
}
return sessionIds;
}
// ------------------------------------------------------ Protected Methods
/**
* Look for a session in the Store and, if found, restore it in the Manager's list of active sessions if
* appropriate. The session will be removed from the Store after swapping in, but will not be added to the active
* session list if it is invalid or past its expiration.
*
* @param id The id of the session that should be swapped in
*
* @return restored session, or {@code null}, if none is found
*
* @throws IOException an IO error occurred
*/
protected Session swapIn(String id) throws IOException {
if (store == null) {
return null;
}
Object swapInLock = null;
/*
* The purpose of this sync and these locks is to make sure that a session is only loaded once. It doesn't
* matter if the lock is removed and then another thread enters this method and tries to load the same session.
* That thread will re-create a swapIn lock for that session, quickly find that the session is already in
* sessions, use it and carry on.
*/
synchronized (this) {
swapInLock = sessionSwapInLocks.computeIfAbsent(id, k -> new Object());
}
Session session = null;
synchronized (swapInLock) {
// First check to see if another thread has loaded the session into
// the manager
session = sessions.get(id);
if (session == null) {
Session currentSwapInSession = sessionToSwapIn.get();
try {
if (currentSwapInSession == null || !id.equals(currentSwapInSession.getId())) {
session = loadSessionFromStore(id);
sessionToSwapIn.set(session);
if (session != null && !session.isValid()) {
log.error(sm.getString("persistentManager.swapInInvalid", id));
session.expire();
removeSession(id);
session = null;
}
if (session != null) {
reactivateLoadedSession(id, session);
}
}
} finally {
sessionToSwapIn.remove();
}
}
}
// Make sure the lock is removed
synchronized (this) {
sessionSwapInLocks.remove(id);
}
return session;
}
private void reactivateLoadedSession(String id, Session session) {
if (log.isTraceEnabled()) {
log.trace(sm.getString("persistentManager.swapIn", id));
}
session.setManager(this);
// make sure the listeners know about it.
((StandardSession) session).tellNew();
add(session);
((StandardSession) session).activate();
// endAccess() to ensure timeouts happen correctly.
// access() to keep access count correct or it will end up
// negative
session.access();
session.endAccess();
}
private Session loadSessionFromStore(String id) throws IOException {
try {
return store.load(id);
} catch (ClassNotFoundException e) {
String msg = sm.getString("persistentManager.deserializeError", id);
log.error(msg, e);
throw new IllegalStateException(msg, e);
}
}
/**
* Remove the session from the Manager's list of active sessions and write it out to the Store. If the session is
* past its expiration or invalid, this method does nothing.
*
* @param session The Session to write out
*
* @throws IOException an IO error occurred
*/
protected void swapOut(Session session) throws IOException {
if (store == null || !session.isValid()) {
return;
}
((StandardSession) session).passivate();
writeSession(session);
super.remove(session, true);
session.recycle();
}
/**
* Write the provided session to the Store without modifying the copy in memory or triggering passivation events.
* Does nothing if the session is invalid or past its expiration.
*
* @param session The session that should be written
*
* @throws IOException an IO error occurred
*/
protected void writeSession(Session session) throws IOException {
if (store == null || !session.isValid()) {
return;
}
try {
store.save(session);
} catch (IOException e) {
log.error(sm.getString("persistentManager.serializeError", session.getIdInternal(), e));
throw e;
}
}
/**
* Start this component and implement the requirements of
* {@link org.apache.catalina.util.LifecycleBase#startInternal()}.
*
* @exception LifecycleException if this component detects a fatal error that prevents this component from being
* used
*/
@Override
protected void startInternal() throws LifecycleException {
super.startInternal();
if (store == null) {
log.error(sm.getString("persistentManager.noStore"));
} else if (store instanceof Lifecycle) {
((Lifecycle) store).start();
}
setState(LifecycleState.STARTING);
}
/**
* Stop this component and implement the requirements of
* {@link org.apache.catalina.util.LifecycleBase#stopInternal()}.
*
* @exception LifecycleException if this component detects a fatal error that prevents this component from being
* used
*/
@Override
protected void stopInternal() throws LifecycleException {
if (log.isTraceEnabled()) {
log.trace("Stopping");
}
setState(LifecycleState.STOPPING);
if (getStore() != null && saveOnRestart) {
unload();
} else {
// Expire all active sessions
Session sessions[] = findSessions();
for (Session value : sessions) {
StandardSession session = (StandardSession) value;
if (!session.isValid()) {
continue;
}
session.expire();
}
}
if (getStore() instanceof Lifecycle) {
((Lifecycle) getStore()).stop();
}
// Require a new random number generator if we are restarted
super.stopInternal();
}
// ------------------------------------------------------ Protected Methods
/**
* Swap idle sessions out to Store if they are idle too long.
*/
protected void processMaxIdleSwaps() {
if (!getState().isAvailable() || maxIdleSwap < 0) {
return;
}
Session sessions[] = findSessions();
// Swap out all sessions idle longer than maxIdleSwap
if (maxIdleSwap >= 0) {
for (Session value : sessions) {
StandardSession session = (StandardSession) value;
synchronized (session) {
if (!session.isValid()) {
continue;
}
int timeIdle = (int) (session.getIdleTimeInternal() / 1000L);
if (timeIdle >= maxIdleSwap && timeIdle >= minIdleSwap) {
if (session.accessCount != null && session.accessCount.get() > 0) {
// Session is currently being accessed - skip it
continue;
}
if (log.isTraceEnabled()) {
log.trace(sm.getString("persistentManager.swapMaxIdle", session.getIdInternal(),
Integer.valueOf(timeIdle)));
}
try {
swapOut(session);
} catch (IOException e) {
// This is logged in writeSession()
}
}
}
}
}
}
/**
* Swap idle sessions out to Store if too many are active
*/
protected void processMaxActiveSwaps() {
if (!getState().isAvailable() || minIdleSwap < 0 || getMaxActiveSessions() < 0) {
return;
}
Session sessions[] = findSessions();
// FIXME: Smarter algorithm (LRU)
int limit = (int) (getMaxActiveSessions() * 0.9);
if (limit >= sessions.length) {
return;
}
if (log.isDebugEnabled()) {
log.debug(sm.getString("persistentManager.tooManyActive", Integer.valueOf(sessions.length)));
}
int toswap = sessions.length - limit;
for (int i = 0; i < sessions.length && toswap > 0; i++) {
StandardSession session = (StandardSession) sessions[i];
synchronized (session) {
int timeIdle = (int) (session.getIdleTimeInternal() / 1000L);
if (timeIdle >= minIdleSwap) {
if (session.accessCount != null && session.accessCount.get() > 0) {
// Session is currently being accessed - skip it
continue;
}
if (log.isTraceEnabled()) {
log.trace(sm.getString("persistentManager.swapTooManyActive", session.getIdInternal(),
Integer.valueOf(timeIdle)));
}
try {
swapOut(session);
} catch (IOException e) {
// This is logged in writeSession()
}
toswap--;
}
}
}
}
/**
* Back up idle sessions.
*/
protected void processMaxIdleBackups() {
if (!getState().isAvailable() || maxIdleBackup < 0) {
return;
}
Session sessions[] = findSessions();
// Back up all sessions idle longer than maxIdleBackup
if (maxIdleBackup >= 0) {
for (Session value : sessions) {
StandardSession session = (StandardSession) value;
synchronized (session) {
if (!session.isValid()) {
continue;
}
long lastAccessedTime = session.getLastAccessedTimeInternal();
Long persistedLastAccessedTime = (Long) session.getNote(PERSISTED_LAST_ACCESSED_TIME);
if (persistedLastAccessedTime != null &&
lastAccessedTime == persistedLastAccessedTime.longValue()) {
continue;
}
int timeIdle = (int) (session.getIdleTimeInternal() / 1000L);
if (timeIdle >= maxIdleBackup) {
if (log.isTraceEnabled()) {
log.trace(sm.getString("persistentManager.backupMaxIdle", session.getIdInternal(),
Integer.valueOf(timeIdle)));
}
try {
writeSession(session);
} catch (IOException e) {
// This is logged in writeSession()
}
session.setNote(PERSISTED_LAST_ACCESSED_TIME, Long.valueOf(lastAccessedTime));
}
}
}
}
}
}