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kubernetescloudmicroservices

Multi-deployment scale k8s

I've explored k8s, yet couldn't find an answer to a not trivial setup I have.

I have 2 apps (2 containers) which work together but not related.
app1 receives and filters data, then sends to app2.

  1. I've decided to have deployment per application;
    1.1. (And not both containers reside in the same POD) because they shouldn't share anything - communication take place on standard network.
    1.2. Each could scale independently

-> Q1 is this approach correct ?

So I have 2 deployments corresponding to these 2 apps. Defined in deployment1.yaml and deployment2.yaml. Each could scale independently with kubectl scale.

My two deployments should work together, so in case of scale I would like to:

  1. Scale both deployment1 and deployment2

-> Q2 Is there a way to perform multi deployment scale with k8s ?

  1. Do something for the newly created instance of deployment1 so it would know of new instance of deployment2 existence (ip address, etc...). i.e. I would like to send some request to it with deployment2 ip.

-> Q3 Is there a way to have some kind of hook for after-successful-scale in order to run some code? e.g. bash script? If there is - who runs it? the master node? Some init container?

Regardless of 3. I would like also deployment1 to pull its configuration from somewhere when it starts. Or alternatively somehow attach files to it when it starts.

-> Q4 Is there a way to do it dynamically? First instance of deployment1 might have different configuration than the second instance. I understand I might use StatefulSets instead of Deployments so I would recognize unique instance.
I thought of using some shared volume / ConfigMap so all instances would read their own unique configuration with their instance number. But I also thought there's a more standard way to do it, so I ask.

I thought what is the way to perform these requirements in the trivial setup of web apps, and thought:

  1. Both deployments scale automatically when need to according to some trigger.
  2. Both deployments export a LoadBalancer, so app1 always talks to app2's LoadBalancer - then deployment1 is really independent from deployment2; both scale and LoadBalancer handles the load.

-> Q5 Is that thought correct for the trivial case?

Solution

  • The more I look at it, the more I understand K8S directly isn't the answer to my requirements.

    I'm implementing a VNF so I need another layer of abstraction.
    Currently I'm looking at OSM which from couple of first glances looks like it has what I need.

    I'll try to update after I know more.