I want to intercept the helm YAML and customize it using a Python script, and then install it. I have been doing something like helm template | python3 script... | kubectl apply -f - but of course this doesn't create a helm release in my cluster, so I lose out on helm rollback etc.
I have considered using Kustomize but it doesn't have the features that I'd like.
Is there a way to take pre-generated YAML, like that from helm template or helm install --dry-run and then install/upgrade that using helm?
Isn't that what post-renderers are for?
See https://helm.sh/docs/topics/advanced/#post-rendering
A post-renderer can be any executable that accepts rendered Kubernetes manifests on STDIN and returns valid Kubernetes manifests on STDOUT. It should return an non-0 exit code in the event of a failure. This is the only "API" between the two components. It allows for great flexibility in what you can do with your post-render process.
A post renderer can be used with install, upgrade, and template. To use a post-renderer, use the --post-renderer flag with a path to the renderer executable you wish to use:
$ helm install mychart stable/wordpress --post-renderer ./path/to/executable
I haven't used it myself yet, but it looks interesting if you want to run your own alternative kustomize.
See https://github.com/vmware-tanzu/carvel-ytt/tree/develop/examples/helm-ytt-post-renderer for an example that is not kustomize.
Related
Why write non-secret metadata as PLACEHOLDER in kubernetes yaml files? (from here):
namespace: PLACEHOLDER
Any reason to replace it with a later sed command? why not simply write it inside the yaml file?
Those values are normally replaced or overridden later, either by sed within a CI/CD pipeline like Jenkins, or (as indicated by the question you linked to) by Helm.
With helm, you can override values within the yamls either with a second yaml, or at the command line using --set switches.
So I could have
helm install nginx --values values.yaml --values values2.yaml
and the placeholder value in values.yaml would get overridden by the value in values2.yaml
Placeholders are often used to deliberately break an install is someone tries to install it without passing in the right values.yaml
For example:
helm install my-chart
Could break because of the placeholder value, but
helm install my-chart --values production.values.yaml
would install because the placeholder values are overridden and the chart can install correctly.
Based on my experience, when you see files like this, they might be used in some sort of pipelines to deploy them in multiple clusters. These files, from my prior experience, act like templates when you don't want to go all in with Helm charts for a single ConfigMap or Secret or a different isolated resource. This allows you to replace these placeholders with values corresponding with you cluster, region etc.
Hope this makes sense.
I have created a helm directory called clickhouse:
Inside the template subdirectory I have a crd.yaml (kind: CustomResourceDefinition) which has to be run before the installation.yaml (kind: ClickHouseInstallation). Right now the installation.yaml is run first when I run the command
$ helm upgrade -i clickhouse ./charts/clickhouse
How do I change the order?
Notes:
I noted that there's a static order by reading through this thread. Since ClickHouseInstallation is not a part of that list I'm curious of how helm orders it and how to change that order.
Also here's the yaml files
crd.yaml
installation.yaml
I think you can try to use Helm hooks like
annotations:
"helm.sh/hook": post-install
Let your crd.yaml have pre-install and then your installation.yaml could have post-install. Please look through the docs for Helm hooks, there might be some downsides in regards to what you want to achieve.
Another way to solve this (might be trivial and not so elegant) would be creating a separate helm chart for the installation.yaml and then just run the crd chart first.
How can I execute "helm install" command and re-install resources that I have defined in "templates"? I have some custom resources that already exist so I want to re-install them. It is possible to do that through a parameter in helm command?
I think your main question is:
I have some custom resources that already exist so I want to re-install them.
Which means DELETE then CREATE again.
Short answer
No.. but it can be done thru workaround
Detailed answer
Helm manages the RELEASE of the Kubernetes manifests by either:
creating helm install
updating helm upgrade
deleting helm delete
However, you can recreate resources following one of these approaches :
1. Twice Consecutive Upgrade
If your chart is designed to enable/disable installation of resources with Values ( .e.g: .Values.customResources.enabled) you can do the following:
helm -n namespace upgrade <helm-release> <chart> --set customResources.enabled=false
# Then another Run
helm -n namespace upgrade <helm-release> <chart> --set customResources.enabled=true
So, if you are the builder of the chart, your task is to make the design functional.
2. Using helmfile hooks
Helmfile is Helm of Helm.
It manage your helm releases within a single file called helmfile.yaml.
Not only that, but it also can call some LOCAL commands before/or/after installing/or/upgrading a Helm release.
This call which happen before or after, is named hook.
For your case, you will need presync hook.
If we organize your helm release as a Helmfile definition , it should be :
releases:
- name: <helm-release>
chart: <chart>
namespace: <namespace>
hooks:
- events: ["presync"]
showlogs: true
command: kubectl
args: [ "-n", "{{`{{ .Release.Namespace }}`}}", "delete", "crd", "my-custom-resources" ]
Now you just need to run helmfile apply
I know that CRD are not namespaced, but I put namespace in the hook just to demonstrate that Helmfile can give you the namespace of release as variable and no need to repeat your self.
You can use helm upgrade to upgrade any existing deployed chart with changes.
The upgrade arguments must be a release and chart. The chart argument can be either: a chart reference(example/mariadb), a path to a chart directory, a packaged chart, or a fully qualified URL. For chart references, the latest version will be specified unless the --version flag is set.
To override values in a chart, use either the --values flag and pass in a file or use the --set flag and pass configuration from the command line, to force string values, use --set-string. In case a value is large and therefore you want not to use neither --values nor --set, use --set-file to read the single large value from file.
You can specify the --values'/'-f flag multiple times. The priority will be given to the last (right-most) file specified. For example, if both myvalues.yaml and override.yaml contained a key called 'Test', the value set in override.yaml would take precedence
For example
helm upgrade -f myvalues.yaml -f override.yaml redis ./redis
easier way I follow, especially for pre existing jobs during helm upgrade is do kubectl delete job db-migrate-job --ignore-not-found
If I run kubectl apply -f <some statefulset>.yaml separately, is there a way to bind the stateful set to a previous helm release? (eg by specifying some tags in the yaml file)
As far as I know - you cannot do it.
Yes, you can always create resources via templates before installing the Helm chart.
However, I have never seen a solution for your question.
I need to pass dynamic env variable to kubectl create. Something like this
kubectl create -f app.yaml --Target=prod
Based on Target code deploys on different servers.
If you want to avoid installing 3rd party plugin then you can replace the text using sed "s/orginal/change/". It worked. I used this in Jenkins shell.
cat app.yaml | sed "s/l3-apps/l2-apps/" | kubectl create -f -
You can achieve this in two ways:
Use Helm. It is a "package manager" for Kubernetes and is built exactly for your use case (dynamic variables to configure behaviour of your resources). If it is only a single variable, "converting" your deployment is as simple as creating a new Helm chart, copy your files into templates/, modify values.yaml and use {{ .Values.target }} in your templates. See the quickstart guide for a more in-depth introduction to Helm.
If you consider Helm to be over the top for a single variable, use kubectl's capability to read from standard input. You'll need an additional templating tool (for example mustache). Rewrite your deployment to fit your templating tool. Create a dynamic data.yml in your deployment process (e.g. a simple bash script that reads from environment variables) and run something like mustache data.yml deployment.mustache | kubectl apply -f -.
kubectl config set-context allows you to configure cluster, namespace, user credentials and more and save it as a "context" in your ~/.kube/config.
The you can use --context option of kubectl exactly in a way that you used --Target in your example.
I've published a command-line tool ysed that also performs what you need.