Kubernetes: one pod, more containers on more nodes

user_1883129 0
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somebody could please help me to create a yaml config file for Kubernetes in order to face a situation like: one pod with 3 containers (for example) and these containers have to be deployed on 3 nodes of a cluster (Google GCE).

|P|      |Cont1| ----> |Node1|
|O| ---> |Cont2| ----> |Node2| <----> GCE cluster
|D|      |Cont3| ----> |Node3|

Thanks

google-compute-engine kubernetes cluster-computing
2 Answers

From Kuberenets Concepts,

Pods in a Kubernetes cluster can be used in two main ways: Pods that run a single container. The “one-container-per-Pod” model is the most common Kubernetes use case; in this case, you can think of a Pod as a wrapper around a single container, and Kubernetes manages the Pods rather than the containers directly. Pods that run multiple containers that need to work together. A Pod might encapsulate an application composed of multiple co-located containers that are tightly coupled and need to share resources. These co-located containers might form a single cohesive unit of service–one container serving files from a shared volume to the public, while a separate “sidecar” container refreshes or updates those files. The Pod wraps these containers and storage resources together as a single manageable entity.

In short, most likely, you should place each container in a single Pod to truly benefit from the microservices architecture vs the monolithic architecture commonly deployed in VMs. However there are some cases where you want to consider co-locating containers. Namely, as described in this article (Patterns for Composite Containers) some of the composite containers applications are:

  • Sidecar containers

extend and enhance the "main" container

  • Ambassador containers

proxy a local connection to the world

  • Adapter containers

standardize and normalize output

Once you define and run the Deployments, the Scheduler will be responsible to select the most suitable placement for your Pods, unless you manually assign Nodes by defining Labels in Deployment's YAML (not recommended unless you know what you're doing).

user_16573090

You can assign multiple containers to a single pod. You can assign pods to a specific node-pool. But I am not sure whether is it possible to assign multiple containers to multiple nodes running in side a single pod.

What you can do here is to assign each container to different pods (3 containers --> 3 pods) and then assign each pod to a different node-pool by adding this code to your deployment's .yaml file.

nodeSelector:
   nodeclass: pool1
user_53004840
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