[jboss-as7-dev] [jboss-as] Fix the default-stateful-access-timeout and default-singleton-access-timeout to be more consistent with the management model, by making them attributes (0b149ef)

[Heiko Braun]

The question you should ask yourself is which parts should be configured externally?
I.e. a typical scenario for expressions are configuration values that change depending on the environment (staging/production).

I would suggest to be _very_ conservative about allowing expressions in your model.
It's definitely wrong to allow them anywhere, just because you are not sure if they make sense.
As Brian said: We can add them anytime, but removing them is not an option.

Some further clarification what "adding expressions" actually means:

a) attribute meta data "expressions-allowed"
b) expressions values that we provide out of the box

a) is a requirement for b). But you are not forced to provide b).

My advice: Support expressions when it makes real sense. But back your decision with some a use case.

Expressions are a powerful way to extend our default configuration means. 
At the same time they lead to ambiguity and all kinds of error scenarios. So use them sparely.


My 2 cents.


Ike

On Oct 11, 2011, at 6:26 PM, Brian Stansberry wrote:

>  But otherwise, go ahead and support 
> it. Expressions will be very important in cloud use cases where 
> customizing the config file on a per-server basis is a poor option.