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helm-integration.md

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Helm Integration with Flux
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Purpose

Helm integration provides an extension to Flux to be able to deal with Helm Chart releases.sp As Helm has gained prominence among Kubernetes tools, Weave Deploy functionality, facilitated by Flux, has been extended to cater for deployments described though Helm Charts.

Design overview

Chart release information is described through Kubernetes Custom Resource (CR) manifests.

Flux-Helm Integration implementation consists of two parts:

  1. Flux agent monitors user git repo containing deployment configuration for applications/services, ie Custom Resource manifests. On detecting changes it applies the manifests, resulting in creation or update of Custom Resources.

  2. Helm operator deals with Helm Chart releases. The operator watches for changes of Custom Resources of kind FluxHelmRelease. It receives Kubernetes Events and acts accordingly, installing, upgrading or deleting a Chart release.

More detail

  • Kubernetes Custom Resource (CR) manifests contain all the information needed to do a Chart release. There is 1-2-1 releationship between a Helm Chart and a Custom Resource.

  • Custom resource manifests can be provided several/all in one file, or in individual files.

  • Flux works, at the moment, with one git repo. For Helm integration this repo will initially contain both the desired Chart release information (CR manifests) and Chart directories for each application/service.

  • All Chart release configuration is located under one git path. All Chart directories are located under one git path. The git paths must be subdirectories under the repo root.

  • Example of Custom Resource manifest:

---
 apiVersion: helm.integrations.flux.weave.works/v1alpha2
 kind: FluxHelmRelease
 metadata:
   name: mongodb
   namespace:  myNamespace
   labels:
     chart: mongodb
 spec:
   chartGitPath: mongodb
   releaseName: mongo-database
   values:
     image: bitnami/mongodb:3.7.1-r1
     resources:
       requests:
         memory: 1024m

  • name of the resource must be unique across all namespaces

  • namespace is where both the Custom Resource and the Chart, whose deployment state it describes, will live

  • labels.chart must be provided. the label contains this Chart's path within the repo (slash replaced with underscore)

  • chartgitpath ... this Chart's path within the repo

  • releasename is optional. Must be provided if there is already a Chart release in the cluster that Flux should start looking after. Otherwise a new release is created for the application/service when the Custom Resource is created. Can be provided for a brand new release - if it is not, then Flux will create a release names as $namespace-$CR_name

  • customizations section contains user customizations overriding the Chart values

  • Helm operator uses (Kubernetes) shared informer caching and a work queue, that is processed by a configurable number of workers.

Setup and configuration

helm-operator requires setup and offers customization though a multitude of flags. (TODO: change the flags to reflect reality)

flag default purpose
--kubernetes-kubectl Optional, explicit path to kubectl tool.
--kubeconfig Path to a kubeconfig. Only required if out-of-cluster.
--master The address of the Kubernetes API server. Overrides any value in kubeconfig. Only required if out-of-cluster.
Tiller options
--tillerIP Tiller IP address. Only required if out-of-cluster.
--tillerPort Tiller port.
--tillerNamespace Tiller namespace. If not provided, the default is kube-system.
Git repo & key etc.
--git-url URL of git repo with Helm Charts; e.g., [email protected]:weaveworks/flux-example
--git-branch master Branch of git repo to use for Kubernetes manifests
--git-charts-path charts Path within git repo to locate Kubernetes Charts (relative path)
repo chart changes (none of these need overriding, usually)
--git-poll-interval 5 minutes period at which to poll git repo for new commits
--chartsSyncInterval 3*time.Minute Interval at which to check for changed charts.
--chartsSyncTimeout 1*time.Minute Timeout when checking for changed charts.
k8s-secret backed ssh keyring configuration
--k8s-secret-volume-mount-path /etc/fluxd/ssh Mount location of the k8s secret storing the private SSH key
--k8s-secret-data-key identity Data key holding the private SSH key within the k8s secret
--queueWorkerCount 2 Number of workers to process queue with Chart release jobs.

Requirements