This PATCH implements the earlier PROPOSAL. namely;
> PROPOSAL: When Session Max reached, throw out oldest session
>
> Currently tomcat ships with the maximum number of sessions set to
> unlimited. They can expire by default after 30 minutes, however if
> too many sessions are created within the 30 minutes, you can run out
> of memory.
>
> To prevent running out of memory, you might choose to limit the
> allowed number of active sessions. If you use the default
> StanardManager (session manager) you can set the "maxActiveSessions"
> to effect a limit. However if you exceed the number of allowed
> sessions, a RuntimeException (IllegalStateException) is thrown.
>
> I propose two changes to reduce seeing these (IllegalStateException or
> OutOfMemory) exceptions for sessions;
>
> 1. When the maximum number of sessions is reached, change
> StandardManager from throwing an IllegalStateException exception, to
> expiring the Least Recently Used (LRUMap) session.
>
> 2. Instead of defaulting to an unlimited number of sessions (and
> getting visits from OutOfMemory), limit the number of sessions to
> 10000 by default.
This PATCH does 1 and 2. It also fixes a problem with recycling
sessions (manager was set to null before session could be recycled.)
Can someone please review this?
Cheers,
-bob
Index: ManagerBase.java
===================================================================
RCS file:
/home/cvspublic/jakarta-tomcat-4.0/catalina/src/share/org/apache/catalina/session/ManagerBase.java,v
retrieving revision 1.11
diff -u -r1.11 ManagerBase.java
--- ManagerBase.java 14 Jan 2002 23:38:03 -0000 1.11
+++ ManagerBase.java 18 Jun 2002 20:47:04 -0000
@@ -73,6 +73,8 @@
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Random;
+import java.util.Map;
+import java.util.Collections;
import org.apache.catalina.Container;
import org.apache.catalina.Engine;
import org.apache.catalina.Logger;
@@ -194,7 +196,7 @@
* The set of currently active Sessions for this Manager, keyed by
* session identifier.
*/
- protected HashMap sessions = new HashMap();
+ protected Map sessions = Collections.synchronizedMap(new HashMap()) ;
/**
@@ -496,11 +498,7 @@
* @param session Session to be added
*/
public void add(Session session) {
-
- synchronized (sessions) {
- sessions.put(session.getId(), session);
- }
-
+ sessions.put(session.getId(), session);
}
@@ -582,11 +580,8 @@
if (id == null)
return (null);
- synchronized (sessions) {
- Session session = (Session) sessions.get(id);
- return (session);
- }
+ return ((Session) sessions.get(id));
}
@@ -595,14 +590,7 @@
* If this Manager has no active Sessions, a zero-length array is returned.
*/
public Session[] findSessions() {
-
- Session results[] = null;
- synchronized (sessions) {
- results = new Session[sessions.size()];
- results = (Session[]) sessions.values().toArray(results);
- }
- return (results);
-
+ return ((Session[]) sessions.values().toArray(new Session[0]));
}
@@ -612,11 +600,7 @@
* @param session Session to be removed
*/
public void remove(Session session) {
-
- synchronized (sessions) {
- sessions.remove(session.getId());
- }
-
+ sessions.remove(session.getId());
}
Index: StandardManager.java
===================================================================
RCS file:
/home/cvspublic/jakarta-tomcat-4.0/catalina/src/share/org/apache/catalina/session/StandardManager.java,v
retrieving revision 1.19
diff -u -r1.19 StandardManager.java
--- StandardManager.java 9 Jun 2002 02:19:43 -0000 1.19
+++ StandardManager.java 18 Jun 2002 20:47:06 -0000
@@ -80,6 +80,8 @@
import java.io.ObjectStreamClass;
import java.util.ArrayList;
import java.util.Iterator;
+import java.util.HashMap;
+import java.util.Collections;
import javax.servlet.ServletContext;
import org.apache.catalina.Container;
import org.apache.catalina.Context;
@@ -93,6 +95,7 @@
import org.apache.catalina.Session;
import org.apache.catalina.util.CustomObjectInputStream;
import org.apache.catalina.util.LifecycleSupport;
+import org.apache.commons.collections.LRUMap;
/**
@@ -138,7 +141,7 @@
/**
* The maximum number of active Sessions allowed, or -1 for no limit.
*/
- private int maxActiveSessions = -1;
+ private int maxActiveSessions = 10000;
/**
@@ -274,6 +277,13 @@
new Integer(oldMaxActiveSessions),
new Integer(this.maxActiveSessions));
+ expireAll();
+
+ if ( max <= 0 )
+ sessions = Collections.synchronizedMap(new HashMap()) ;
+ else
+ sessions = Collections.synchronizedMap(new LocalLRUMap(max) );
+
}
@@ -314,29 +324,6 @@
// --------------------------------------------------------- Public Methods
-
- /**
- * Construct and return a new session object, based on the default
- * settings specified by this Manager's properties. The session
- * id will be assigned by this method, and available via the getId()
- * method of the returned session. If a new session cannot be created
- * for any reason, return <code>null</code>.
- *
- * @exception IllegalStateException if a new session cannot be
- * instantiated for any reason
- */
- public Session createSession() {
-
- if ((maxActiveSessions >= 0) &&
- (sessions.size() >= maxActiveSessions))
- throw new IllegalStateException
- (sm.getString("standardManager.createSession.ise"));
-
- return (super.createSession());
-
- }
-
-
/**
* Load any currently active sessions that were previously unloaded
* to the appropriate persistence mechanism, if any. If persistence is not
@@ -353,7 +340,10 @@
// Initialize our internal data structures
recycled.clear();
- sessions.clear();
+ if ( maxActiveSessions <= 0 )
+ sessions = Collections.synchronizedMap(new HashMap() );
+ else
+ sessions = Collections.synchronizedMap(new LocalLRUMap(maxActiveSessions)
+);
// Open an input stream to the specified pathname, if any
File file = file();
@@ -414,7 +404,7 @@
((StandardSession) session).activate();
}
} catch (ClassNotFoundException e) {
- log(sm.getString("standardManager.loading.cnfe", e), e);
+ log(sm.getString("standardManager.loading.cnfe", e), e);
if (ois != null) {
try {
ois.close();
@@ -425,7 +415,7 @@
}
throw e;
} catch (IOException e) {
- log(sm.getString("standardManager.loading.ioe", e), e);
+ log(sm.getString("standardManager.loading.ioe", e), e);
if (ois != null) {
try {
ois.close();
@@ -492,7 +482,6 @@
}
// Write the number of active sessions, followed by the details
- ArrayList list = new ArrayList();
synchronized (sessions) {
if (debug >= 1)
log("Unloading " + sessions.size() + " sessions");
@@ -502,7 +491,6 @@
while (elements.hasNext()) {
StandardSession session =
(StandardSession) elements.next();
- list.add(session);
((StandardSession) session).passivate();
session.writeObjectData(oos);
}
@@ -537,18 +525,7 @@
throw e;
}
- // Expire all the sessions we just wrote
- if (debug >= 1)
- log("Expiring " + list.size() + " persisted sessions");
- Iterator expires = list.iterator();
- while (expires.hasNext()) {
- StandardSession session = (StandardSession) expires.next();
- try {
- session.expire(false);
- } catch (Throwable t) {
- ;
- }
- }
+ expireAll();
if (debug >= 1)
log("Unloading complete");
@@ -664,18 +641,7 @@
log(sm.getString("standardManager.managerUnload"), e);
}
- // Expire all active sessions
- Session sessions[] = findSessions();
- for (int i = 0; i < sessions.length; i++) {
- StandardSession session = (StandardSession) sessions[i];
- if (!session.isValid())
- continue;
- try {
- session.expire();
- } catch (Throwable t) {
- ;
- }
- }
+ expireAll();
// Require a new random number generator if we are restarted
this.random = null;
@@ -714,6 +680,31 @@
// -------------------------------------------------------- Private Methods
+ /**
+ * extention of commons LRUMap, handles expiration and works around
+ * an LRU bug
+ */
+ private class LocalLRUMap extends LRUMap {
+ LocalLRUMap(int max) {
+ super(max);
+ }
+
+ protected void processRemovedLRU(Object key, Object value){
+ ((Session)value).expire();
+ log("StandardManager: WARNING Max sessions reached, expiring oldest
+key:"+key);
+ }
+
+ // collections 2.0 has a bug in it - fixed in the latest CVS
+ public Object get(Object key){
+
+ // put() it to move it to the top of the LRU
+ if ( containsKey( key ) ){
+ put( key, super.get(key));
+ }
+ return super.get(key);
+ }
+ };
+
/**
* Return a File object representing the pathname to our
@@ -823,6 +814,27 @@
thread = null;
+ }
+
+
+ /**
+ * Expire all active sessions
+ */
+ private void expireAll(){
+
+ Session list[] = findSessions();
+ for (int i = 0; i < list.length; i++) {
+ StandardSession session = (StandardSession) list[i];
+ if (!session.isValid())
+ continue;
+ try {
+ session.expire();
+ } catch (Throwable t) {
+ ;
+ }
+ }
+
+ sessions.clear();
}
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