So what you are saying is that even with replication enabled, asynchronous replication CAS clusters should have sticky sessions on regardless? I realize that synchronous replication CAS cluster have no need of sticky sessions seeing as how it goes to all servers before the user can move on.
Andrew On 10/23/08 9:29 PM, "Scott Battaglia" <[EMAIL PROTECTED]> wrote: > It actually shouldn't matter if the async works or not. The memcache clients > are designed to hash to a particular server and only check the backup servers > if the primary isn't available. > > So you should always be validating against the original server unless its no > longer there. > > -Scott > > -Scott Battaglia > PGP Public Key Id: 0x383733AA > LinkedIn: http://www.linkedin.com/in/scottbattaglia > > > On Thu, Oct 23, 2008 at 9:17 PM, Adam Rybicki <[EMAIL PROTECTED]> wrote: >> >> Scott, >> >> I have run into a issue with MemCacheTicketRegistry and was wondering if you >> have any thoughts. I didn't want to create a new thread for this note. >> Anyone else with comments should feel free to reply, too. ;-) >> >> My tests have shown that when a ticket is generated on a CAS cluster member >> it may sometimes fail to validate. This is apparently because the memcached >> asynchronous replication did not manage to send the ticket replica in time. >> Fast as repcached may be, under a relatively light load, ST validation failed >> in 0.1% of the cases, or once in 1000 attempts. It would seem that the >> following tasks should be fairly complex: >> * Browser accesses a CAS-protected service >> * Service redirects to CAS for authentication >> * CAS validates the TGT >> * CAS issues the ST for service >> * CAS redirects the browser to service >> * Service sends the ST for validation >> But they are fast! My jMeter testing showed this taking 28 milliseconds >> under light load on CAS server , which is amazingly fast. Please note that >> in real life, this can be just as fast because the browser, CAS, and service >> perform these steps without the user slowing them down. CAS is indeed a >> lightweight system, and memcached does nothing to slow it down. It seems >> that in 0.1% of the cases this outperforms repcached under light load. The >> bad news is that under heavy load the failure rate increases. I've seen as >> bad as 8% failure rate. >> >> Have you or anyone else seen this? Have you had to work around this? >> >> Thanks, >> Adam >> >> Scott Battaglia wrote: >>> >>> On Tue, Oct 14, 2008 at 11:15 AM, Andrew Ralph Feller, afelle1 >>> <[EMAIL PROTECTED]> wrote: >>> >>> >>>> >>>> Hey Scott, >>>> >>>> Thanks for answering some questions; really appreciate it. Just a handful >>>> more: >>>> >>>> >>>> 1. What happens whenever the server it intends to replicate with is down? >>>> >>>> >>> >>> It doesn't replicate :-) The client will send its request to the primary >>> server and if the primary server is down it will replicate to the secondary. >>> The repcache server itself will not replicate to the other server if it >>> can't find it. >>> >>> >>>> >>>> >>>> 1. >>>> 2. >>>> 3. What happens whenever it comes back up? >>>> >>>> >>> >>> The repcache servers will sync with each other. The memcache clients will >>> continue to function as they should >>> >>> >>>> >>>> >>>> 1. >>>> 2. >>>> 3. Does the newly recovered machine synchronize itself with the other >>>> servers? >>>> >>>> >>> >>> The newly recovered machine with synchronize with its paired memcache >>> server. >>> >>> -Scott >>> >>> >>>> >>>> >>>> 1. >>>> 2. >>>> >>>> Thanks, >>>> Andrew >>>> >>>> >>>> On 10/14/08 9:56 AM, "Scott Battaglia" <[EMAIL PROTECTED] >>>> <http://[EMAIL PROTECTED]> > wrote: >>>> >>>> >>>> >>>>> >>>>> Memcache, as far as I know, uses a hash of the key to determine which >>>>> server to write to (and then with repcache, its replicated to its pair, >>>>> which you configure). >>>>> >>>>> -Scott >>>>> >>>>> -Scott Battaglia >>>>> PGP Public Key Id: 0x383733AA >>>>> LinkedIn: http://www.linkedin.com/in/scottbattaglia >>>>> >>>>> >>>>> On Tue, Oct 14, 2008 at 10:38 AM, Andrew Ralph Feller, afelle1 >>>>> <[EMAIL PROTECTED] <http://[EMAIL PROTECTED]> > wrote: >>>>> >>>>> >>>>>> >>>>>> Scott, >>>>>> >>>>>> I've looked at the sample configuration file on the JA-SIG wiki, however >>>>>> I was curious how memcached handles cluster membership for lack of a >>>>>> better word. One of the things we are getting burned on by JBoss/Jgroups >>>>>> is the frequency the cluster is being fragmented. >>>>>> >>>>>> Thanks, >>>>>> Andrew >>>>>> >>>>>> >>>>>> >>>>>> >>>>>> >>>>>> On 10/14/08 8:58 AM, "Scott Battaglia" <[EMAIL PROTECTED] >>>>>> <http://[EMAIL PROTECTED]> <http://[EMAIL PROTECTED]> > >>>>>> wrote: >>>>>> >>>>>> >>>>>> >>>>>>> >>>>>>> We've disabled the registry cleaners since memcached has explicit time >>>>>>> outs (which are configurable on the registry). We've configured it by >>>>>>> default with 1 gb of RAM I think, though I doubt we need that much. >>>>>>> >>>>>>> -Scott >>>>>>> >>>>>>> -Scott Battaglia >>>>>>> PGP Public Key Id: 0x383733AA >>>>>>> LinkedIn: http://www.linkedin.com/in/scottbattaglia >>>>>>> >>>>>>> >>>>>>> >>>>>>> >>>>>>> On Mon, Oct 13, 2008 at 11:41 PM, Patrick Hennessy <[EMAIL PROTECTED] >>>>>>> <http://[EMAIL PROTECTED]> <http://[EMAIL PROTECTED]> > wrote: >>>>>>> >>>>>>> I've been working on updating from 3.2 to 3.3 and wanted to give memcached a try instead of JBoss. I read Scott's message about performance and we've had good success here with memcached for other applications. It also looks like using memcached instead of JBoss will simplify the configuration changes for the CAS server. I do have the JBoss replication working with CAS 3.2 but pounding the heck out of it with JMeter will cause some not so nice stuff to happen. I'm using VMWare VI3 and configured an isolated switch for the clustering and Linux-HA traffic. I do see higher traffic levels coming to my cluster in the future, but I'm not sure if they'll meet the levels from my JMeter test. (I'm just throwing this out there because of the recent Best practice thread.) If I use memcached, is the ticketRegistryCleaner not needed anymore? I left those beans in the ticketRegistry.xml file and saw all kinds of errors. After taking it out it seems to load fine and appears to work, but I wasn't sure what the behavior is and I haven't tested it further. What if memcached fills up all the way? Does anyone have a general idea of how much memory to allocate to memcached with regards to concurrent logins and tickets stored? Thanks, Pat -- =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= Patrick Hennessy ([EMAIL PROTECTED] <http://[EMAIL PROTECTED]> <http://[EMAIL PROTECTED]> ) Senior Systems Specialist Division of Information and Educational Technology Delaware Technical and Community College =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= _______________________________________________ Yale CAS mailing list [email protected] <http://[email protected]> <http://[email protected]> http://tp.its.yale.edu/mailman/listinfo/cas >>>>>>> >>>>>>> >>>>>>> >>>>>>> >>>>>>> _______________________________________________ >>>>>>> Yale CAS mailing list >>>>>>> [email protected] <http://[email protected]> >>>>>>> <http://[email protected]> >>>>>>> >>>>>>> http://tp.its.yale.edu/mailman/listinfo/cas >>>>>>> >>>>>>> >>>>>> >>>>> >>>> >>>> >>>> -- >>>> Andrew R. Feller, Analyst >>>> Information Technology Services >>>> 200 Fred Frey Building >>>> Louisiana State University >>>> Baton Rouge, LA 70803 >>>> (225) 578-3737 (Office) >>>> (225) 578-6400 (Fax) >>>> >>>> >>>> >>>> _______________________________________________ >>>> Yale CAS mailing list >>>> [email protected] >>>> http://tp.its.yale.edu/mailman/listinfo/cas >>>> >>>> >>> >>> >>> >>> >>> >>> >>> _______________________________________________ >>> Yale CAS mailing list >>> [email protected] >>> http://tp.its.yale.edu/mailman/listinfo/cas >>> >> >> _______________________________________________ >> Yale CAS mailing list >> [email protected] >> http://tp.its.yale.edu/mailman/listinfo/cas >> > > > > _______________________________________________ > Yale CAS mailing list > [email protected] > http://tp.its.yale.edu/mailman/listinfo/cas -- Andrew R. Feller, Analyst Information Technology Services 200 Fred Frey Building Louisiana State University Baton Rouge, LA 70803 (225) 578-3737 (Office) (225) 578-6400 (Fax)
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