[infinispan-dev] Infinispan and OpenShift/Kubernetes PetSets

[Alan Field]

A little late to the discussion but if all of the pods share the same set of volumes, couldn't you also use the FILE_PING discovery protocol between the pods? 

Thanks, 
Alan 

----- Original Message -----

> From: "Sebastian Laskawiec" <slaskawi at redhat.com>
> To: "infinispan -Dev List" <infinispan-dev at lists.jboss.org>, "Bela Ban"
> <bban at redhat.com>, "Kevin Conner" <kconner at redhat.com>, "Rob Cernich"
> <rcernich at redhat.com>
> Sent: Friday, August 19, 2016 5:00:12 AM
> Subject: [infinispan-dev] Infinispan and OpenShift/Kubernetes PetSets

> Hey!

> I've been playing with Kubernetes PetSets [1] for a while and I'd like to
> share some thoughts. Before I dig in, let me give you some PetSets
> highlights:

> * PetSets are alpha resources for managing stateful apps in Kubernetes 1.3
> (and OpenShift Origin 1.3).
> * Since this is an alpha resource, there are no guarantees about backwards
> compatibility. Alpha resources can also be disabled in some public cloud
> providers (you can control which API versions are accessible [2]).
> * PetSets allows starting pods in sequence (not relevant for us, but this is
> a killer feature for master-slave systems).
> * Each Pod has it's own unique entry in DNS, which makes discovery very
> simple (I'll dig into that a bit later)
> * Volumes are always mounted to the same Pods, which is very important in
> Cache Store scenarios when we restart pods (e.g. Rolling Upgrades [3]).

> Thoughts and ideas after spending some time playing with this feature:

> * PetSets make discovery a lot easier. It's a combination of two things -
> Headless Services [4] which create multiple A records in DNS and predictable
> host names. Each Pod has it's own unique DNS entry following pattern:
> {PetSetName}-{PodIndex}.{ServiceName} [5]. Here's an example of an
> Infinispan PetSet deployed on my local cluster [6]. As you can see we have
> all domain names and IPs from a single DNS query.
> * Maybe we could perform discovery using this mechanism? I'm aware of DNS
> discovery implemented in KUBE_PING [7][8] but the code looks trivial [9] so
> maybe it should be implement inside JGroups? @Bela - WDYT?
> * PetSets do not integrate well with OpenShift 'new-app' command. In other
> words, our users will need to use provided yaml (or json) files to create
> Infinispan cluster. It's not a show-stopper but it's a bit less convenient
> than 'oc new-app'.
> * Since PetSets are alpha resources they need to be considered as secondary
> way to deploy Infinispan on Kubernetes and OpenShift.
> * Finally, the persistent volumes - since a Pod always gets the same volume,
> it would be safe to use any file-based cache store.

> If you'd like to play with PetSets on your local environment, here are
> necessary yaml files [10].

> Thanks
> Sebastian

> [1] http://kubernetes.io/docs/user-guide/petset/
> [2] For checking which APIs are accessible, use 'kubectl api-versions'
> [3]
> http://infinispan.org/docs/stable/user_guide/user_guide.html#_Rolling_chapter
> [4] http://kubernetes.io/docs/user-guide/services/#headless-services
> [5] http://kubernetes.io/docs/user-guide/petset/#peer-discovery
> [6] https://gist.github.com/slaskawi/0866e63a39276f8ab66376229716a676
> [7] https://github.com/jboss-openshift/openshift-ping/tree/master/dns
> [8] https://github.com/jgroups-extras/jgroups-kubernetes/tree/master/dns
> [9] http://stackoverflow.com/a/12405896/562699
> [10] You might need to adjust ImageStream.
> https://gist.github.com/slaskawi/7cffb5588dabb770f654557579c5f2d0

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