Cyclic Dependency in Helm Charts

Oct 13, 2025 by wbrum.org 30 views

Introduction

When working with Helm charts, especially those with complex dependencies, issues can arise that hinder the smooth deployment of applications. In this article, we will delve into a specific problem encountered while using the [blockscout-stack] migration job, which is unable to utilize secret resources due to a Helm hook pre-install issue. We will explore the root cause of this problem, which is a cyclic dependency in the chart, and provide a solution to resolve this issue.

Understanding the Issue

The problem lies in the blockscout-migration-job.yaml file, where an envFromSecret map is defined to include secrets. However, this setup is not compatible with the Helm chart's lifecycle, particularly when the chart is not yet released and the secrets are not available. This creates a cyclic dependency, making it challenging to use the secret resources.

Cyclic Dependency in Helm Charts

A cyclic dependency in Helm charts occurs when two or more resources depend on each other, creating a loop. In this case, the blockscout-migration-job.yaml file depends on the secrets, which are not yet available due to the chart's lifecycle. This creates a situation where the migration job is unable to use the secret resources.

Helm Hook Pre-Install Issue

The Helm hook pre-install issue is a critical component of this problem. When the chart is not yet released, the secrets are not available, and the Helm hook pre-install fails to execute. This failure prevents the migration job from using the secret resources, leading to a deployment failure.

Solution: Resolving the Cyclic Dependency

To resolve the cyclic dependency and the Helm hook pre-install issue, we need to modify the blockscout-migration-job.yaml file. We can achieve this by removing the envFromSecret map and instead using a different approach to inject the secrets into the migration job.

Alternative Approach: Using a ConfigMap

One possible solution is to use a ConfigMap to store the secrets and then inject them into the migration job. This approach allows us to decouple the migration job from the secrets, breaking the cyclic dependency.

Step 1: Create a ConfigMap

First, we need to create a ConfigMap to store the secrets. We can do this by adding a new file, configmap.yaml, to the chart's directory:

apiVersion: v1
kind: ConfigMap
metadata:
  name: blockscout-migration-job-config
data:
  SECRET_KEY: <secret_key>
  SECRET_VALUE: <secret_value>

Step 2: Update the Migration Job

Next, we need to update the blockscout-migration-job.yaml file to use the ConfigMap instead of the envFromSecret map:

apiVersion: batch/v1
kind: Job
metadata:
  name: blockscout-migration-job
spec:
  template:
    spec:
      containers:
      - name: blockscout-migration-job
        image: <image_name>
        env:
        - name: SECRET_KEY
          valueFrom:
            configMapKeyRef:
              name: blockscout-migration-job-config
              key: SECRET_KEY
        - name: SECRET_VALUE
          valueFrom:
            configMapKeyRef:
              name: blockscout-migration-job-config
              key: SECRET_VALUE

Step 3: Update the Helm Chart

Finally, we need to update the Helm chart to use the new ConfigMap. We can do this by modifying the values.yaml file:

blockscout-migration-job:
  configMap:
    name: blockscout-migration-job-config

Conclusion

In this article, we explored the issue of the [blockscout-stack] migration job being unable to use secret resources due to a Helm hook pre-install issue. We identified the root cause of the problem, which is a cyclic dependency in the chart, and provided a solution to resolve this issue. By using a ConfigMap to store the secrets and injecting them into the migration job, we were able to break the cyclic dependency and deploy the application successfully.

Best Practices

When working with Helm charts, it's essential to follow best practices to avoid issues like the one described in this article. Some best practices include:

Avoid cyclic dependencies: Be mindful of the dependencies between resources in your chart and avoid creating cyclic dependencies.
Use ConfigMaps: Use ConfigMaps to store sensitive data, such as secrets, and inject them into your applications.
Test thoroughly: Thoroughly test your chart and applications to ensure that they work as expected.

Introduction

In our previous article, we explored the issue of the [blockscout-stack] migration job being unable to use secret resources due to a Helm hook pre-install issue. We identified the root cause of the problem, which is a cyclic dependency in the chart, and provided a solution to resolve this issue. In this article, we will answer some frequently asked questions (FAQs) related to this issue.

Q: What is a cyclic dependency in a Helm chart?

A: A cyclic dependency in a Helm chart occurs when two or more resources depend on each other, creating a loop. In the case of the [blockscout-stack] migration job, the blockscout-migration-job.yaml file depends on the secrets, which are not yet available due to the chart's lifecycle.

Q: Why is the Helm hook pre-install failing?

A: The Helm hook pre-install is failing because the chart is not yet released, and the secrets are not available. This creates a situation where the migration job is unable to use the secret resources.

Q: How can I resolve the cyclic dependency?

A: To resolve the cyclic dependency, you can use a ConfigMap to store the secrets and inject them into the migration job. This approach allows you to decouple the migration job from the secrets, breaking the cyclic dependency.

Q: What is a ConfigMap, and how can I use it?

A: A ConfigMap is a Kubernetes resource that stores sensitive data, such as secrets. You can use a ConfigMap to store the secrets and inject them into your applications. To use a ConfigMap, you need to create a new file, configmap.yaml, to store the secrets and then update the blockscout-migration-job.yaml file to use the ConfigMap.

Q: How can I update the Helm chart to use the new ConfigMap?

A: To update the Helm chart to use the new ConfigMap, you need to modify the values.yaml file to include the ConfigMap name and then update the blockscout-migration-job.yaml file to use the ConfigMap.

Q: What are some best practices to avoid issues like this?

A: Some best practices to avoid issues like this include:

Avoid cyclic dependencies: Be mindful of the dependencies between resources in your chart and avoid creating cyclic dependencies.
Use ConfigMaps: Use ConfigMaps to store sensitive data, such as secrets, and inject them into your applications.
Test thoroughly: Thoroughly test your chart and applications to ensure that they work as expected.

Q: Can I use other approaches to resolve the cyclic dependency?

A: Yes, you can use other approaches to resolve the cyclic dependency, such as using a separate chart for the secrets or using a different method to inject the secrets into the migration job. However, using a ConfigMap is a recommended approach as it is a simple and effective solution.

Conclusion

In this article, we answered some frequently asked questions related to the issue of the [blockscout-stack] migration job being unable to use secret resources due to a Helm hook pre-install issue. We provided a solution to resolve the cyclic dependency and recommended best practices to avoid issues like this in the future.

Additional Resources

For more information on Helm charts and Kubernetes, please refer to the following resources:

We hope this article has been helpful in resolving the issue of the [blockscout-stack] migration job being unable to use secret resources due to a Helm hook pre-install issue. If you have any further questions or need additional assistance, please don't hesitate to contact us.