Expose parameterlist of current inform to the session context

[okraits]

This commit exposes the parameterlist of the current inform to the session context to enable the user to access it in a provision script via the path Events.Inform.ParameterList.

A valid usecase would be to check the parameterlist for any parameter of interest and then trigger needed actions to respond to the value change of that parameter.

[jameswmcnab]

This would be perfect for sending events to an external application (via a external script that uses HTTP or Redis pub-sub etc) when an inform occurs.

Do the provisions ever run at a time that is not triggered by an Inform?

[zaidka]

I've been thinking about this after it was discussed in the mailing list a while back. This solution, while simple and straight forward, is not caching friendly. In a future release I plan to implement caching for provisions to skip executing a provision script if we know it won't have an effect (provision scripts are guaranteed to be idempotent). Not to go into details of how that works, the fact that you're representing all inform parameter names in a single parameter will cause unnecessary cache invalidation. If each inform parameter is to be represented separately then that would solve the caching problem.

[zaidka]

Do the provisions ever run at a time that is not triggered by an Inform?

No. @jameswmcnab

[okraits]

Ok, so I want to propose the following modification:

• add a NumberOfEntries parameter containing the number of inform parameters
• present every inform parameter as a separate entry (possibly with the new value)

[okraits]

@zaidka Any opinion about this?

[okraits]

@zaidka I rewrote the patch. Now every inform parameter is added separately, with both path and value.

Please review.

[jameswmcnab]

Any reason this can't be merged now the cache invalidation issue is resolved @zaidka?