K
Q

Kubernetes Workflow

9/2/2016

I have been using kubernetes for a while now.

$ kubectl version                                                                                    
Client Version: version.Info{Major:"1", Minor:"3", GitVersion:"v1.3.0+2831379", GitCommit:"283137936a
498aed572ee22af6774b6fb6e9fd94", GitTreeState:"not a git tree", BuildDate:"2016-07-05T15:40:25Z", GoV
ersion:"go1.6.2", Compiler:"gc", Platform:"darwin/amd64"}                                            
Server Version: version.Info{Major:"1", Minor:"2", GitVersion:"v1.2.0", GitCommit:"5cb86ee022267586db
386f62781338b0483733b3", GitTreeState:"clean", BuildDate:"", GoVersion:"", Compiler:"", Platform:""}

I usually set an Ingress, Service and Replication Controller for each project.

apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  namespace: portifolio
  name: portifolio-ingress
spec:
  rules:
  - host: www.cescoferraro.xyz
    http:
      paths:
      - path: /
        backend:
          serviceName: portifolio
          servicePort: 80
---
apiVersion: v1
kind: Service
metadata:
  namespace: portifolio
  name: portifolio
  labels:
    name: portifolio
spec:
  selector:
    name: portifolio
  ports:
  - name: web
    port: 80
    targetPort: 80
    protocol: TCP

---
apiVersion: v1
kind: ReplicationController
metadata:
  namespace: portifolio
  name: portifolio
  labels:
    name: portifolio
spec:
  replicas: 1
  selector:
    name: portifolio
  template:
    metadata:
      namespace: portifolio
      labels:
        name: portifolio
    spec:
      containers:
        - image: cescoferraro/portifolio:latest
          imagePullPolicy: Always
          name: portifolio
          env:
          - name: KUBERNETES
            value: "true"
          - name: BRANCH
            value: "production"

My "problem" is that for deploying my app I usually do:

kubectl -f delete kubernetes.yaml
kubectl -f create kubernetes.yaml

I wish I could use a single command to deploy, whenever my app is up or down. Rolling updates do not work when I use the same image,(I think its a bug on my kubernetes server version). But it also do not work when the app has never been deployed at all.

I have read about Deployments, I wonder how it would help me?

Goals 1. Deploy if app is brand new 2. Replace existing pods with new ones using a new image from docker registry.

-- CESCO
coreos
docker
kubernetes

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4 Answers

5/26/2017

You could use a deployment for this. Create it the first time, and after that you only need to do kubectl set image deploy/my-app app=user/image:tag --record and you're good to go.

Doing that, you can also do cool things like kubectl rollout undo deploy/my-app or get history and status.

-- caarlos0
Source: StackOverflow
9/10/2017

You might consider using Argo.

Argo is an open-source workflow engine for Kubernetes. It allows to define complex microservices-based application deployment using YAML in source repo and automatically re-deploy app on YAML change (e.g. on every commit to production branch) .

-- Alexander Matyushentsev
Source: StackOverflow
9/3/2016

I don't think keeping all resources inside one single manifest helps you with what you want to achieve, since your Service, Ingress and ReplicationController are not likely to change simultaneously.

If all you want to do is roll out new pods, I would recommend you to replace your ReplicationController with a Deployment. Manifests have almost the exact same syntax so it's easy to migrate from standard RCs, and you could perform a server-side rolling update with a single kubectl replace -f manifest.yml.

Please note that even with a Deployment resource you can't trigger a redeployment if nothing changed in your manifest. kubectl replace would just do nothing. Therefore you could for example increment or change a tag inside your manifest in order to force the deployment, if needed (eg. revision: 003).

-- Antoine Cotten
Source: StackOverflow
2/19/2017

As already written in the previous answer, it is recommended to use a Deployment instead of a ReplicationController for this.

Using imagePullPolicy: Always will only ensure that Kubernetes does a docker pull before starting new PODs. It does not force recreation of PODs when nothing in the Deployment resource changes.

I would suggest to add 2 things to your solution:

  • Add a label to the Deployment with the value CURRENT_DATE as a placeholder value
  • Add a simple shell script to your project which replaces the placeholder with the current date+time and then uses kubectl to apply the resources.

Example Bash script

#!/usr/bin/env bash

sed "s/CURRENT_DATE/$(date)/" kubernetes.yaml | kubectl apply -f -

Then use this script for redeployment instead of calling kubectl by yourself.

This is only meant as a very simple example. When it comes to creating/applying/patching resources in Kubernetes, things tend to get more and more complicated by time. If this happens, consider using some more advanced templating solutions, e.g. by using Python and Jinja2.

-- Alexander Block
Source: StackOverflow