I have multiple charts that all use the same templates. Is it possible to instruct helm to use some other templates directory, or have some shared templates that I can import/reference in some way? I would like to avoid the copy paste and have reusable templates, but at the same time keep the project/service per chart because in the future there will be some discrepancies.
How do you achieve DRY and re-usability in helm?
To me, that sounds like you want to use so called "Library Charts" ( link to helm docs).
To create one, you define a helm chart that does not actually create any Resources but only defines reusable templates and set the type property in the chart.yml to library:
apiVersion: v2
name: library-chart
description: A Helm chart for Kubernetes
type: library
version: 0.0.1
Then, you can include that helm chart as a dependency in your other charts and start using the templates defined there.
Related
For a regular helm-chart I can use helm package --app-version="foo-bar" to be able to overwrite app-version while packing the helm chart.
Is there a way to achieve the same with sub-charts.
Consider the following helm-chart structure
uber-chart
\sub-chart-1
\sub-chart-2
\sub-chart-3
Is it possible to pass different app-versions to different sub-charts while packaging uber-chart?
I have a parent chart which contains 4 subcharts, out of these I want to deploy the 1 specific subchart to different namespace and all the template files in that subchart are referring to {{ .Release.Namespace. }}. Is their any way to modify the .Release.Namespace. of subchart from the parent chart?
I don't believe this is possible using vanilla Helm and charts you don't control.
When a chart depends on a subchart, there's fairly little that it's possible to customize. The parent chart can provide a default set of values for the subchart, but nothing computed, and those can be overridden by the person running helm install.
If, and only if, the subchart is specifically written to deploy into an alternate namespace
# Every object in the subchart must have this configuration
metadata:
namespace: {{ .Values.namespace | default .Release.Namespace }}
then you could supply that value to the subchart; but this isn't a default configuration.
My general experience has been that Helm "umbrella charts" are inflexible in a couple of important ways. There are higher-level tools like Helmfile and Helmsman that provide a single-command installation of multiple Helm charts with a full set of options (Helmsman is simpler, Helmfile allows Helm-style templating almost everywhere which is both more powerful and more complex). If you need to install four charts, three into one namespace and one into another, these tools might work better.
Currently, I have 2 Helm Charts - Chart A, and Chart B. Both Chart A and Chart B have the same dependency on a Redis instance, as defined in the Chart.yaml file:
dependencies:
- name: redis
version: 1.1.21
repository: https://kubernetes-charts.storage.googleapis.com/
I have also overwritten Redis's name since applying the 2 Charts consecutively results in 2 Redis instances, as such:
redis:
fullnameOverride: "redis"
When I try to install Chart A and then Chart B I get the following error:
Error: rendered manifests contain a resource that already exists. Unable to continue with install: existing resource conflict: kind: PersistentVolumeClaim, namespace: default, name: redis
I was left with the impression that 2 charts with identical dependencies would use the same instance if it's already present?
When you install a chart using Helm, it generally expects each release to have its own self-contained set of Kubernetes objects. In the basic example you show, I'd expect to see Kubernetes Service objects named something like
release-a-application-a
release-a-redis
release-b-application-b
release-b-redis
There is a general convention that objects are named starting with {{ .Release.Name }}, so the two Redises are separate.
This is actually an expected setup. A typical rule of building microservices is that each service contains its own isolated storage, and that services never share storage with each other. This Helm pattern supports that, and there's not really a disadvantage to having this setup.
If you really want the two charts to share a single Redis installation, you can write an "umbrella" chart that doesn't do anything on its own but depends on the two application charts. The chart would have a Chart.yaml file and (in Helm 2) a requirements.yaml file that references the two other charts, but not a templates directory of its own. That would cause Helm to conclude that a single Redis could support both applications, and you'd wind up with something like
umbrella-application-a
umbrella-application-b
umbrella-redis
(In my experience you usually don't want this – you do want a separate Redis per application – and so trying to manage multiple installations using an umbrella chart doesn't work especially well.)
Unfortunately, Helm can't handle multiple resources with the same name or in other word there isn't any share resource capability.
You can follow This issue
I think you can use kustomize template to use share resources. There is a really good kustomize vs helm article.
I need to install a helm chart with a key/value that is not present in one of the templates and I prefer not to edit the already existing templates.
In particular, I need to change resources.limits.cpu and resources.limits.memory in k8s-job-template.yaml but resources is not even mentioned in that file.
Is there a solution for this?
The only customizations it's possible to make for a Helm chart are those the chart author has written in; you can't make arbitrary additional changes to the YAML files.
(Kustomize allows merges of arbitrary YAML content and is built into recent kubectl, but it doesn't have some of the lifecycle or advanced templating features of Helm.)
For future reference, I found a solution to this.
Simply download the chart using the following command:
helm fetch <chart> --untar --destination /local/path/to/chart
Go to the folder /local/path/to/chart/<chartname> and make the desired changes.
After this, simply install the helm chart based on the locally edited chart:
helm install /local/path/to/chart/<chartname>
Is there a way to create own boilerplate helm chart and then generate from it helm charts for my micro services (which will differ only in chart names)?
Yes, you'd need to create a package of your base boilerplate chart and then reference it in the requirements.yaml for other charts which depend on it.
Ref: https://helm.sh/docs/developing_charts/#chart-dependencies
Use helm create command to create boiler template, then changes are up to yourself.
$ helm create mychart
Ref: https://helm.sh/docs/helm/#helm-create