Best way to enable and disable cacheloader and eviction

[ben.wang]

In the previous version of JBossCache, to enable/disable a feature, we simply specify an empty string to the provider class. For example, for the tm, if we specify:

 <attribute name="TransactionManagerLookupClass"></attribute>

then there is not tx involved. Same thing for eviction policy and cache loader.

However, in 1.3 (for cache loader) and 1.4 (for eviction), since we support chained cache loader and multiple eviction regions, one single class doesn't cut it anymore.

As a result, when you need to disable either loader or eviction feature, you will need to either delete or comment out the xml element.

Now, comment it out is fine except if you have many regions (or many loader) configured and you have embeded comments there already. Then it becomes tedious.

So may be it is just me who is old fashion. :-) But how about we provide an explit flag to enable/disable these features? This way, we decouple the activation from the configuration details.

How about UseEviction and UseCacheLoader flags in 1.4?

[manik]

I'm okay with it, just concerned about making the configuration more and more complex from an end-user's point of view. What do others think?

[hmesha]

+1

I think it's great idea to have switches for different parts of the configurations. From user stand point, It's logically intuitive that using a feature requires turing on the switch and configuring it.

Hany

[brian.stansberry]

What's the default for these, and what's the behavior if the feature is enabled, but not configured?

My inclination would be that they are enabled by default, but nothing bad (i.e. nothing more than an INFO level log message) happens if the relevant feature isn't configured. Effect is you only need to add the new attribute to your config if you want to *turn off* the feature.

[ben.wang]

Default is no eviction and no cache loader. Turning on eviction by default is not a good idea since it involves a separate eviction timer thread. So we would only create it if user wants it in the first place.

Besides the switches, other thing is if we externalize the interceptor stacks in the next 2.0 release, for example. Then, the interceptor such as EvictionInterceptor, StoreInterceptor can also act as a switch as well, albeit it not that explicitly.