[Hawkular-dev] OpenShift Pet vs Cattle metaphor

[Jiri Kremser]

Hello,
  today, I was on L&L about storage in OpenShift and I learn interesting
thing. I always thought, that everything needs to be immutable and
stateless and all the state needs to be handled by means of NFS persistent
volumes. Luckily, there is a feature in Kubernetess (since 1.3) that allows
the PODs to be treated as pets. It's called PetSet [1] and it assigns a
unique ID (and persistent DNS record) to a POD that runs in this "mode".

Common use-case for PetSet is a set of pods with a relational DBs that uses
some kind of master-slave replication and slaves needs to know the master's
address. But it can be used for anything. We can use the hostname as the
feed id for instance.

I don't know how much this will be popular because it kind of defeats the
purpose of immutable infrastructure but it can save us some work with the
feed identity. And of course we need to support also the "normal" POD
scenario.


[1]: http://kubernetes.io/docs/user-guide/petset/

jk
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