Anand Sambamoorthy

Solutions Architect, Engineer

@asamba
San Jose, CA
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Kubernetes Helm - Deploying Multiple Apps(containers) Using SubCharts

Published Sep 01, 2019

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This is my first real post in the newly setup my GitHub Page and using Markdown.

This post is stemming with my play-work with kubernetes where I wanted to install multiple apps (containers/services) with a single command. The rescue came in the way of Helm - A package manager for Kubernetes. This will describe how to install/manage multiple apps (containers/services). You might want to reference Using Helm and Kubernetes for a single application deployment.

Applications Topology

Sno App Type App Name
1 Parent greeting-app
2 Child-1 helloworld
3 Child-2 hiworld


Step-1: Create the Services

Create Child Service - helloworld

  • A simple spring-boot service - add a RestController /hello that returns “Hello World” or alternatively create a static page /resources/static/hello.html that returns “Hello World!”
  • Create a docker image and push that to the docker-hub
% mvn package
% docker build -t asamba/helloworld:v1 
% docker push asamba/helloworld:v1
# replace asamba with your own dockerhub repo

Create Child Service - hiworld

  • A simple spring-boot service - add a RestController /hi that returns “Hi World” or alternatively create a static page /resources/static/hi.html that returns “Hi World!”
  • Create a docker image and push that to the docker-hub
% mvn package
% docker build -t asamba/hiworld:v1 
% docker push asamba/hiworld:v1

Step-2: Create the Charts & Package with Subcharts

Create Subchart for Child application - helloworld & hiworld

  • Generate sample chart using helm create helloworld - this should create a folder helloworld with sub-folders/files inside.
  • Delete templates/tests, ingress.yaml and remove the ingress references in NOTES.txt
  • Edit the values.yaml file to look like following. Note: I am using NodePort you can try LoadBalancer if on cloud. A very nice post on the topic is at When should I use what?
replicaCount: 1

image:
  repository: asamba/helloworld
  tag: v1
  pullPolicy: IfNotPresent

service:
  type: NodePort
  port: 8080

#template deployment.yaml has this value to be injected and is not part of the generation
#you may be fine if you use the spring-boot container server.port as 80
containerPort:
  port: 8080

  • Verify the chart with helm lint helloworld and ensure there are no errors. Verify actual yamls that will be generated by helm template helloworld

  • Generate sample chart for hiworld similar to the above and the values.yaml updated and test with helm lint hiworld

Create Chart for Parent application - greeting

  • Generate sample chart using helm create greetings
  • Delete all the files unders templates/ folder
  • Create a new file requirements.yaml under greetings/ with the below content
  • Copy the subcharts ‘helloworld’ and ‘hiworld’ inside the greetings/charts folder
dependencies:
  - name: helloworld
  - name: hiworld

Note: This approach can be reversed as well. You can create the parent chart and then create the subcharts by helm create helloworld and helm create hiworld inside the greetings/charts folder. Either way the end result is the same - you will have subcharts inside the parent chart.

Step-3: Deploy the app

helm install --name greetings-app greetings

  • This should deploy the greetings-app with the other 2 child applications with the associated containers/services.
  • You can see the status of the ‘greetings-app’ with helm status greetings-app and you should see the o/p as below which gives the list of deployments, pods and the services by the ‘greetings-app’ install.
STATUS: DEPLOYED

RESOURCES:
==> v1/Deployment
NAME                      READY  UP-TO-DATE  AVAILABLE  AGE
greetings-app-helloworld  1/1    1           1          38h
greetings-app-hiworld     1/1    1           1          38h

==> v1/Pod(related)
NAME                                       READY  STATUS   RESTARTS  AGE
greetings-app-helloworld-664d648c94-mvsvv  1/1    Running  0         38h
greetings-app-hiworld-76745bc9ff-84k64     1/1    Running  0         38h

==> v1/Service
NAME                      TYPE      CLUSTER-IP      EXTERNAL-IP  PORT(S)         AGE
greetings-app-helloworld  NodePort  10.107.151.148  <none>       8080:30647/TCP  38h
greetings-app-hiworld     NodePort  10.100.165.29   <none>       8080:30565/TCP  38h

You can package the application with helm package as described in the helm documentation or the tutorial at Using Helm and Kubernetes

Step-2 (Alternative - Dependency Chart Creation)

Another way to create the dependent-child applications are as below

  • Package your child applications with helm package and host in a http server; best hosted with github and create the requirements.yaml as below (sample)
dependencies:
  - name: helloworld-app
    repository: https://raw.githubusercontent.com/asamba/myhelmcharts/master/
    version: 0.1.0
    tags:
      - helloworld
  - name: hiworld-app
    repository: https://raw.githubusercontent.com/asamba/myhelmcharts/master/
    version: 0.1.0
    tags:
      - hiworld

Note: the above method is the preferred method for creating dependent applications say- you want to create a database for a service.

In summary - Helm is awesome and helps you to package applications and manage (install, delete, upgrade, rollback) with a single command. No more multiple files need to be run in seq like kubectl apply -f hiworld-deployment.yaml kubectl apply -f hiworld-service.yaml for each application you want to maintain along with common ones like ingress.yaml etc.

References