Helm Dry Run: A Guide for Effective Chart Validation

Helm dry run, using the helm install --dry-run command, is a valuable technique for validating Helm charts before deployment on a Kubernetes cluster. It helps avoid errors and unexpected behavior by simulating the installation process without modifying the cluster. Helm dry run works alongside other Helm commands like helm template and helm lint to streamline development and ensure charts are well-structured, compatible, and ready for deployment.

This guide explores Helm dry run, a valuable technique for validating Helm charts before deployment on a Kubernetes cluster.

What is Helm?

Helm simplifies managing applications within Kubernetes clusters. It packages application configurations as Helm charts, which include deployment manifests and configuration details.

Why Use Helm Dry Run?

Validating Helm charts before deployment helps avoid introducing errors or unexpected behavior to your cluster. Helm dry run allows you to test a chart without modifying your cluster’s state.

Key Helm Commands for Chart Validation

helm template: Generates the output manifest file based on a Helm chart’s templates and variables. Useful for reviewing the chart’s structure and identifying syntax errors.

$ helm create mychart

$ helm template mychart mychart
---
# Source: mychart/templates/serviceaccount.yaml
apiVersion: v1
kind: ServiceAccount
metadata:
name: mychart
labels:
helm.sh/chart: mychart-0.1.0
app.kubernetes.io/name: mychart
app.kubernetes.io/instance: mychart
app.kubernetes.io/version: "1.16.0"
app.kubernetes.io/managed-by: Helm
<--- snip --->

helm lint: Performs static analysis on a Helm chart, checking for potential issues like best practice deviations or suspicious code constructs. Ideal during chart development.The helm lint command is run like this:

$ helm lint mychart
==> Linting mychart
[INFO] Chart.yaml: icon is recommended

1 chart(s) linted, 0 chart(s) failed

helm install — dry-run: Attempts to install the chart without modifying the cluster. Validates the generated manifest against the Kubernetes API server, ensuring compatibility with your cluster’s version and configuration.After the edits, the command will succeed:

$ helm install mychart mychart --dry-run
NAME: mychart
LAST DEPLOYED: Sat Jul 22 09:57:03 2023
NAMESPACE: default
STATUS: pending-install
REVISION: 1
HOOKS:
---
# Source: mychart/templates/tests/test-connection.yaml
apiVersion: v1
kind: Pod
metadata:

<--- snip --->

Using Helm Dry Run

helm template: This command generates the manifest file but doesn’t validate its contents as a valid Kubernetes manifest. Use the --debug flag to see the output even if it contains invalid YAML.
helm lint: Run this command on your Helm chart to identify potential issues during development.
helm install — dry-run: This command simulates the installation process by sending the generated manifest to the Kubernetes API server for verification. If the manifest is valid and compatible with your cluster, the command will succeed. Conversely, it will report errors if there are issues with the manifest or chart configuration.

Benefits of Helm Dry Run

Early detection of errors: Identify and fix issues before deploying the chart to your production cluster.
Improved chart quality: Helm dry run promotes well-structured and validated Helm charts.
Reduced risk of deployment failures: Mitigate the chance of disruptions caused by invalid or incompatible charts.

Conclusion

Helm dry run is a powerful tool for streamlining Helm chart development and deployment. By incorporating these techniques into your workflow, you can ensure your charts are well-structured, compatible, and ready for deployment on your Kubernetes clusters.

Read the entire article with complete details here:

Helm Dry Run: Guide & Best Practices | Squadcast

Learn how to use Helm dry run to troubleshoot templates and preview what a Helm chart will do.

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Squadcast is a cloud-based software designed around Site Reliability Engineering (SRE) practices with best-of-breed Incident Management & On-call Scheduling capabilities.