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Fall 2009 Day 2 - Terracotta

Fall 2009 Day 2 - Terracotta

Oct 01, 2009

TERRACOTTA

  • Hibernate

    • cache raw compenent types, no objects

    • 1st level cache (tied to db connection, goes away when db connection
      goes away)

    • 2nd level cache (avoid going back to db, pluggable, ehcache most
      common, terracotta another option)

      • needs to be across cluster for writing data

  • ehcache

    • option for clusterwide Hibernate 2nd cache

    • uPortal boxes all have to talk to eachother, get 5-10 becomes problem, exponentially chatty

  • Terracotta (open source)

    • option for clusterwide Hibernate 2nd cache

      • could use it directly as well

    • advantages in clustering, sharding 

      • separate service, not run on uPortal boxes

      • less "chatty", all uPortal boxes talk to same terracotta box, this
        allows "sharding" (see below)

      • keeps data as Hibernate 2nd level objects (however those are done), like a shared memory for all uPortal boxes, "network attached memory" (like NAS for memory)

      • mark a particular part of application object as "distributed"

      • could be called an object oriented db, persists all of its cache to disk

      • data persists until orphaned, then its garbage collection

    • use to cluster Tomcat http sessions

      • does it better that Tomcat own session clustering for same
        "chattiness" issue

      • still doesn't get around serializable requirement, but has config option in case you can't serialize in Java code

    • Big Savings: "sharding", only possible with terracotta's less-chatty architecture, terracotta will only push one box's cache to other boxes when other boxes look for it

    • ? should people worry about clustering with uPortal?

    • Cris doesn't see big value to clustering http options, e.g. Madison only gets 1.7 requests per login, little chance for failover there

    • important for Sakai, e.g. things go boom in the middle of an exam

    • UofC will be in between

    • uPortal, 2nd level Hibernate cache for layout

    • trend in uPortal has been that session cache is becoming more serializable

  • Stuff going on

    • Sakai

      • Cris used in Sakai instance for John Wiley&Son, will be part of
        Sakai 2.7 (code freeze Nov. 20 to meet late Winter/early Spring release)

      • capabilities will be in Sakai, up to implementers to turn it on

      • with it on you should be able to fail over without having to log back in

      • for app specific things, e.g. an exam, you can terracotta-enable tool by tool, some tools don't have much state and don't need it

    • Hibernate 2nd level thing is huge

      • uPortal session is possibility, Eric has been thinking about it

      • Cris interested in finding uPortal instance where big gains can be made with terracotta

    • sidenote: there is a way to plug terracotta behind an ehcache

    • terracotta can be used without Hibernate, use configs to cache without app even knowing (good and bad)

      • "super static" - local static class attr, cluster in terracotta config, now static across cluster, not just local JVM

    • Webinar on changes made to Sakai October 29th 10:30 am pacific

    • possible alternative to db, does data really need to be in a db? e.g. Sakai "presence" data

    • questions? Talk to Cris, also the Terracotta guys are very accessible