In regards to the Lateral cache and three servers. I noticed a bug back
in June in regards to having more than 2 laterally configured cache
servers. It is a few lines of code to fix and from what I could tell,
three or more lateral servers will not work correctly without the fix.
I checked the laters LateralCacheFactory from the trunk and did not
notice the fix. All of the information from the email is below.
-----Original Message-----
From: Baum, Karl
To: Turbine JCS Developers List
Sent: 6/15/2003 10:22 PM
Subject: TCP Lateral Caching bug fix
I noticed a problem with lateral caching when configuring two or more
TCP servers. The problem has to do with lateral cache recovery process
when losing connections. I have attached a fix.
Main Issue:
I have three lateral cache servers. I start one server first. Because
the other lateral TCP servers are not yet running, the first server
fails to connect to the others and begins recovery mode. In recovery
mode, a LateralCacheMonitor thread runs every 20 seconds trying to
create connections to the other servers. I noticed the thread was only
trying to create a connection to one of the other cache servers. The
result was that when I brought the other two servers up, the initial
server only successfully connected to one out of the other two servers.
This was always the last of the TCP servers in the comma separated list.
Cause:
The problem is caused by the reuse of the same LateralCacheAttributes
object. For each of the TCP servers, a LateralCacheManager is created.
Each LateralCacheManager is created with an instance of
LateraCacheAttributes. Before instantiating the LateralCacheManager,
the specific TCP server is set on the LateralCacheAttributes object.
Since the same instance of LateralCacheAttributes is used each time, the
call to set the TCP server overwrites the previous TCP server each time.
In recovery mode, the TCP server property on the LateralCacheAttributes
is used to reestablish the connections. Recovery mode will always
attempt to reestablish a connection to the last of the TCP servers since
this was the last server to be set in the LateralCacheAttributes object.
Fix:
To fix this issue, I modified the class LateralCacheFactory. Now
LateralCacheFactory calls set TCP server on a clone of the
LateralCacheAttributes object. As a result, the previous TCP server is
not overwritten.
CVS diff:
$ cvs -d :pserver:[EMAIL PROTECTED]:/home/cvspublic diff -u
LateralCacheFactory.java
Index: LateralCacheFactory.java
===================================================================
RCS file:
/home/cvspublic/jakarta-turbine-jcs/src/java/org/apache/jcs/auxiliary/la
teral/LateralCacheFactory.java,v
retrieving revision 1.4
diff -u -r1.4 LateralCacheFactory.java
--- LateralCacheFactory.java 7 Aug 2002 15:28:12 -0000 1.4
+++ LateralCacheFactory.java 16 Jun 2003 02:14:43 -0000
@@ -73,15 +73,16 @@
StringTokenizer it = new StringTokenizer( lac.tcpServers,
"," );
while ( it.hasMoreElements() )
{
+ LateralCacheAttributes lacClone =
(LateralCacheAttributes)lac.copy();
//String server = (String)it.next();
String server = ( String ) it.nextElement();
if ( log.isDebugEnabled() )
{
log.debug( "tcp server = " + server );
}
- lac.setTcpServer( server );
- LateralCacheManager lcm =
LateralCacheManager.getInstance( lac );
- ICache ic = lcm.getCache( lac.getCacheName() );
+ lacClone.setTcpServer( server );
+ LateralCacheManager lcm =
LateralCacheManager.getInstance( lacClone );
+ ICache ic = lcm.getCache( lacClone.getCacheName() );
if ( ic != null )
{
noWaits.add( ic );
<<LateralCacheFactory.java>> <<LateralCacheAttributes.java>>
<<LateralCacheFactory.java>>
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