Add support for twin life-cycle events

[w4tsn]

In order to integrate other components and services of an infrastructure for some use-cases it's crucial to act on life-cycle events of a twin. E.g. to register the twin on it's creation with monitoring, etc. Or to de-register when it is decommissioned.

Therefore the connectivity, HTTP and websocket APIs need means to filter for those events only. Otherwise one would have to listen on a potentially large data stream to manually fish out life-cycle events.

There is certainly even more potential in this concept, so let's discuss!

[thjaeckle]

This makes sense, yes.
Would you also expect "lifecycle events" for e.g. created/removed features? I think that could be useful as well.
On a feature property/attribute level however I don't think that e.g. "attribute created" as separate lifecycle event would be so useful.

Regarding syntax: we would have to support it in the RQL queries, some ideas:

• eq(__lifecycle,"CREATED") and eq(__lifecycle,"DELETED")
• ... ?

[w4tsn]

For the features part, nice addition! I could think of RQL queries for those like this eq(__lifecycle/features/lamp,"CREATED").

So I'm currently further tracking life cycle states which might be really use-case dependent and not that helpful for a general implementation. Would have to think about that a bit more first, but here you go:

• ACTIVE as in "put into duty" to mark that the device history is written to prod systems and those kind of things so we keep the initialization stuff separated from production
• INACTIVE if the device is relocated, receives off the grid maintenance / upgrades or other things which are not considered "production updates"
• RETIRED to mark that this device is now put out of service and maybe deleted or archived for later reference (our devices have unique IDs that also tie together history, alerting etc.)

I agree that property/attribute level events seem to be a bit over-kill

[thlandgraf]

Hi,

in our systems, we have a period of calibration validity (in german "Eichgültigkeit") in our lifecycle. Maybe, a "OUT_OF_GUARANEE" makes also sense.

best
   Thomas

[thjaeckle]

Hi @thlandgraf
That sounds like a rather domain specific lifecycle (Ditto is domain agnostic) - can't this be an attribute instead?
On attributes, searching and filtering is already supported.

[thjaeckle]

We start working on this issue.
The suggested approach is to make it possible to use topic:action (see connection scoped placeholders) in RQL expressions, e.g.:

eq(topic:action,'created')

or(eq(topic:action,'created'),eq(topic:action,'deleted'))

and(eq(topic:action,'created'),eq(attributes/location,'kitchen'))

Targeted is only the lifecycle of the thing/twin (as the title of the issue also suggests), feature lifecycle is out of scope for this issue.