[Hawkular-dev] Inventory: transient feeds - or how to tackle the pets vs cattle scenario

[Heiko W.Rupp]

Hey,

Right now we identify "agents" via their feed-id.
An instrumented wildfly comes online, registers
its feed with the server, sends its resource discovery
and later metrics with the feed id.
Over its lifecycle, the server may be stopped and re-started
several times.

This is great in the classical use case with installations
on tin or VMs.

In container-land especially with systems like Kubernetes,
containers are started once and after they have died for
whatever reason they are not restarted again.
So the id of an individual container is less and less interesting.
The interesting part is the overall app, that contains of many
containers linked together with several of them representing
an individual service of the app.

So basically we would rather need to record the app and other
metadata for identifying individual parts of the app (e.g. the web
servers or the data bases) and then get pointers to individual
stuff.
The feed would not need to survive for too long, but some of
its collected data perhaps. And then e.g. the discovery of resources
in a new container of the exact same type as before should be sort
of a no-op, as we know this already. Could we short-circuit that
by storing the docker-image-hash (or similar) and once we see this
known one abort the discovery?

Another aspect is certainly that we want to keep (some) historic
records of the died container - e.g. some metrics and the point
when it died. Suppose k8s kills a container and spins a new one
up (same image) on a different node, then logically it is a continuation
of the first one, but in a different place (but they have different feed
ids)

Now a more drastic scenario: As orchestration systems like k8s or
Docker-Swarm have their own registries, that can be queried : do we need 
a
hawkular-inventory for this at all?

( We still need it for the non-OpenShift/K8s/Docker-Swarm envs )

-- 
Reg. Adresse: Red Hat GmbH, Technopark II, Haus C,
Werner-von-Siemens-Ring 14, D-85630 Grasbrunn
Handelsregister: Amtsgericht München HRB 153243
Geschäftsführer: Charles Cachera, Michael Cunningham, Michael O'Neill, 
Eric Shander