helm-stack

What

Deploy your docker-compose stack with Helm.

If you ever ask yourself, what do this thousand lines of k8s manifest or that monstrous helm chart does behind the scene, this chart may be what you were waiting for so long.

TL;DR

helm repo add link https://linktohack.github.io/helm-stack/
kubectl create namespace your-stack
# docker stack deploy -c docker-compose.yaml your_stack
helm -n your-stack upgrade --install your-stack link/stack -f docker-compose.yaml

While the inter-container communication is enabled in swarm either by network or link, in k8s if you have more than one service and they need to communicate together, you will need to expose the ports explicitly by --set services.XXX.expose={YYYY}

Features (complete)

The chart is features complete and I was able to deploy complex stacks with it including traefik and kubernetes-dashboard. In all cases, there is a mechanism to override the generated manifests with full possibilities of k8s API (see below.)

Acceptable configurations can be found in the test:.

Example

Dockersamples

Tested in a K3s cluster with local-path provisioner.

❯ helm -n com-linktohack-docker-on-compose upgrade --install sample link/stack -f test/docker-compose-dockersamples.yaml
Release "sample" does not exist. Installing it now.
NAME: sample
LAST DEPLOYED: Tue Jan 14 18:38:42 2020
NAMESPACE: com-linktohack-docker-on-compose
STATUS: deployed
REVISION: 1
TEST SUITE: None

❯ kubectl get all -n com-linktohack-docker-on-compose                                                                                                                                                                                                     stack/git/master 
NAME                                   READY   STATUS    RESTARTS   AGE
pod/svclb-web-loadbalancer-tcp-hk9sb   1/1     Running   0          2m2s
pod/web-57bbd888fb-dvqxj               1/1     Running   0          2m2s
pod/db-769769498d-6zqx8                1/1     Running   0          2m2s
pod/words-6465f956d-kmk9c              1/1     Running   0          2m2s
pod/words-6465f956d-sw9t2              1/1     Running   0          2m2s
pod/words-6465f956d-vchlm              1/1     Running   0          2m2s
pod/words-6465f956d-l9lnd              1/1     Running   0          2m2s
pod/words-6465f956d-2lsbz              1/1     Running   0          2m2s

NAME                       TYPE           CLUSTER-IP      EXTERNAL-IP   PORT(S)           AGE
service/web-loadbalancer   LoadBalancer   10.43.235.241   2.56.99.175   33000:31908/TCP   2m4s

NAME                                    DESIRED   CURRENT   READY   UP-TO-DATE   AVAILABLE   NODE SELECTOR   AGE
daemonset.apps/svclb-web-loadbalancer   1         1         1       1            1           <none>          2m4s

NAME                    READY   UP-TO-DATE   AVAILABLE   AGE
deployment.apps/web     1/1     1            1           2m4s
deployment.apps/db      1/1     1            1           2m4s
deployment.apps/words   5/5     5            5           2m4s

NAME                              DESIRED   CURRENT   READY   AGE
replicaset.apps/web-57bbd888fb    1         1         1       2m4s
replicaset.apps/db-769769498d     1         1         1       2m4s
replicaset.apps/words-6465f956d   5         5         5       2m4s

More complex examples

Please see below.

Extra keys

These keys are either not existed in docker-compose format or have the meaning changed. They’re should be set via --set or second values.yaml.

Advance: Full override

Raw property allows us to deploy arbitrary manifests, but most of time, there is a better way.

The properties of the manifests can be overridden (merged) with the values from services.XXX.Kind and volumes.XXX.Kind…

You will now have full control of the output manifests. While this is a deep merge operation, the item in the list will be also merged if existed, new items will be also inserted.

The full list of all the Kinds can be found in the listing below, please note that services.XXX.imagePullPolicy, volumes.XXX.storage, configs.XXX.data secrets.XXX.stringData are already recognized as extra keys.

services:
  redmine:
    ClusterIP: {}
    NodePort: {}
    LoadBalancer: {}
    Ingress:
      default: {} # default segement
      seg1: {} # segment seg1
    Auth:
      default: {}
      seg: {} # segment seg1
    Deployment:
      spec:
        template:
          spec:
            containers:
              - name: override-name
                imagePullPolicy: Always # supported as an extra key already
    DaemonSet:
      spec:
    StatefulSet:
      spec:
    Job:
      spec:
    CronJob:
      spec:
        schedule: '*/1 * * * *' # mostly require
volumes:
  db:
    PV:
      spec:
        capacity:
          storage: 10Gi # supported as an extra key already
        persistentVolumeReclaimPolicy: Retain
    PVC:
      spec:
        resources:
          requests:
            storage: 10Gi # supported as an extra key already
configs:
  redmine_config:
    ConfigMap:
      data:
        hello.yaml: there
secrets:
  with_string_data:
    Secret:
      stringData: ""

How

Golang template + Sprig are quite a pleasure to work as a full-feature language.

Why

Blog post https://linktohack.com/posts/evaluate-options-to-migrate-from-swarm-to-k8s/

The same technique can be applied via a proper language instead of using a Helm template but why not standing on the shoulders of giant(s). By using Helm (the de facto package manager) we’re having the ability rollback and so on… for free.

Other works

Contribution

More examples

Redmine + MySQL

This example contains almost all the possible configurations of this stack.

helm -n com-linktohack-redmine upgrade --install redmine link/stack -f test/docker-compose-redmine.yaml -f test/docker-compose-redmine-override.yaml \
    --set services.db.expose={3306:3306} \
    --set services.db.ports={3306:3306} \
    --set services.db.deploy.placement.constraints={node.role==manager} \
    --set services.redmine.deploy.placement.constraints={node.role==manager} \
    --set chdir=/stack --debug --dry-run

Traefik ingress

helm -n kube-system upgrade --install traefik link/stack -f test/docker-compose-traefik.yml -f test/docker-compose-traefik-override.yml

Kubernetes dashboard (with basic auth and skip login)

helm -n kubernetes-dashboard upgrade --install dashboard link/stack -f test/docker-compose-kubernetes-dashboard.yml

Via template

helm -n com-linktohack-redmine template redmine link/stack -f test/docker-compose-redmine.yaml -f test/docker-compose-redmine-override.yaml \
    --set services.db.expose={3306:3306} \
    --set services.db.ports={3306:3306} \
    --set services.db.deploy.placement.constraints={node.role==manager} \
    --set services.redmine.deploy.placement.constraints={node.role==manager} \
    --set chdir=/stack --debug > test/docker-compose-redmine.manifest.yaml
kubectl -n com-linktohack-redmine apply -f test/docker-compose-redmine.manifest.yaml

Changelog

License

This project is licensed under Fair Source License with a revenue-based threshold.

See LICENSE.md for full terms.

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