Re: Terracotta integration

Stefan Fußenegger wrote:

As I said, it's a matter of taste and not worth a discussion. I think I can handle it, if you want to stick with your solution ;)

With "complain" I meant: "All changes to clustered objects must happen within the context of a Terracotta transaction. This means that a thread must acquire a clustered lock prior to modifying the state of any clustered objects. If a thread attempts to modify a clustered object outside the context of a terracotta transaction, a runtime exception will be thrown." (Terracotta Product Documentation). PageMapStore is clustered after being stored in the session. Therefore, modifications to PageMapStore._pageMaps (as in getPageMap(String)) will cause an exception outside of a transaction. I can't see where the transaction starts, but testing this in a clustered environment will quickly give an answer whether we need further synchronization or not (maybe you already did this, while I only tested without actually using TC clustering). I added the further synchronization if needed

btw: getPageStore(...) should probably be renamed as it in fact returns a PageMapStore, not a PageStore, same for getPageMap(...) that returns a PageStore.

i think a nice side effect of this new implementation is that wicket components need not be IClusterable anymore. we always test our app in "pure wicket mode" and test it clustered prior to deployment. we always find some objects that are Serializable but not IClusterable, hence causing exceptions with TC. Using serialization of pages, both modes would need Serializable objects only.

regards
stefan

OurTerracottaPageStore.java

richardwilko wrote:

Looks good,

Stefan Fußenegger wrote:

- I wouldn't use an extra class just to wrap a HashMap of PageStore. I would just put them into the plain session. But finally, this is just a matter of taste. I even think that this class lacks proper synchronization. Doesn't Terracotta complain about modifying an instance outside of a transaction??

I disagree, I think it makes the code cleaner as all the stuff to do with creating PageStores (and debug information) is encapsulated in the class.  I don't think that the synchronisation is an issue, im not sure what you mean about terracotta complaining,  if Ari is still watching this thread then he can probably answer the question.

It is a pain that you cant get the last element of the list, but your solution works well, I tweaked it slightly to remove a not needed if statement (you dont need to check the page id, the subset stuff takes care of it).

I'm gonna put this slightly modified class through our test environment here where i work and throw loads of simulated users at it to see how it works.

I have removed the wicket module from my terracotta config as this currently forces the use of httpsessionstore.  Also with our solution we only need to instrument 4 classes so i'm not using the IClusterable thing in the config, i'm just declaring the classes manually.
I would be good to find out how we go about modifying the wicket tim (probably another question for Ari there).  I downloaded the terracotta source but couldn't get it to build.

Richard