Kubernetes Manifest Files: Complete Guide with Examples and Best Practices

Now that your company has decided to embrace cloud-native and microservices software architecture, you've suddenly been thrust into the whimsical, and somewhat confusing, world of Kubernetes. So, let's get down to research. Put on your learning hat and let's dive into Kubernetes Manifest files, the foundation of your cloud-native testing infrastructure…

What is a Kubernetes Manifest file?

A Kubernetes Manifest file is a YAML or JSON file that describes the desired state of a Kubernetes object. These objects can include deployment, replica set, service, and more. Manifest files define the specifications of the object, such as its metadata, properties, and desired state.

Also known as a YAML or JSON file, it describes the desired state of a Kubernetes object: deployment, replica set, service etc…

Simple, yah?

But don't underestimate the needs of your Desired State. Manifest files are powerful tools that allow developers to deploy, scale and manage your Kubernetes clusters, and when it comes to cloud-native continuous testing with Testkube, they ultimately enable consistent testing infrastructure that (hopefully) makes your deployment and testing life easier.

Speaking of, what exactly is a "Desired State" when it comes to Kubernetes Manifests?

Simply put, it's the state you want your objects to be in (I guess you could say, it's your ideal "manifestation" ha. ha.) including the images used, number of replicas, and anything else you desire! Once you've clearly visualized your Desired State, Kubernetes acts to automatically deploy and manage your carefully crafted object, keeping it in its "Desired State". This is especially crucial for testing workloads that need to run reliably across different environments and scales.

Understanding Kubernetes Manifests

Before you can create or manage Kubernetes objects, whether for applications or testing infrastructure, you must first understand the importance of Manifests:

Kubernetes Manifests are composed of three parts:

1. ‍Metadata which includes object labels, name and annotations‍
2. Specification which defines the desired state of the kubernetes object, its properties and configurations.
3. And finally, Status: the section that describes the true state of an object, the number of replicas and your current version.

Example of Kubernetes Manifest Files

Below, is what your Manifest File should look like:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: my-deployment
spec:
  replicas: 3
  selector:
    matchLabels:
      app: my-app
  template:
    metadata:
      labels:
        app: my-app
    spec:
      containers:
      - name: my-container
        image: my-image:latest
        ports:
        - containerPort: 80

This example defines a deployment object with three replicas. It includes a Pod template with one container and uses the image "my-image:latest" and is listening on containerPort: 80.

Remember, the syntax and structure of your Manifest File will vary depending on the defined resource. Make sure to review, and test to ensure successful deployment and management of your Kubernetes Clusters. This becomes even more critical when deploying testing infrastructure that needs to integrate seamlessly with your existing cloud-native stack and support various testing frameworks across your development pipeline.

Common Errors in Kubernetes Manifests

So, what exactly does an error in a Kubernetes Manifest look like? Well, the most common errors are YAML formatting errors, property names with simple typos, invalid values and JSON syntax errors.

But, in my experience, the most common error is similar to what I do with my keys: forgetting. Specifically, forgetting to include required properties for your objects like image names for containers.

Fortunately, with proper validation and testing tools, you can catch these specification errors before they impact your testing infrastructure deployment.

Enough about my chaotic morning, let's take a closer look at some of these errors, shall we?

YAML File Format Errors

Formatting YAML Errors can cause a whole slew of fun problems to solve, here are some of the typos we see regularly:

Missing colon after a property name

containers:
  name my-app  # Missing colon after 'name'

Missing closing quotation mark

env:
- name: MY_ENV_VAR
  value: "my-value  # Missing closing quote

Incorrect indentation

env:
- name: MY_ENV_VAR
value: "my-value"  # Incorrect indentation

Property Name Typos

Misspelled property names in Kubernetes Manifests can easily cause issues with deployment and application management. Make an English teacher proud and check, double check and triple check that all your property names are spelled correctly and match the specifications of the defined object.

Misspelled property names come in a variety of flavors, like the heavy handed "imageee" instead of "image" or swapping "prot" instead of "port". Careful eyes, or adding another pair of fresh ones, can help catch these errors before it's too late…

Invalid Values for Properties

Invalid values for properties can really mess up your deployment and management.

Specifying non-existent images can confuse your deployment the same way pretending to throw the ball confuses your poor dog. Make sure the ball is real, and ensure that all your property values are valid, and match the specifications of any object being defined. This is especially important for testing workloads where image availability and proper configuration directly impact your ability to execute tests reliably in your Kubernetes infrastructure.

Best Practices for Kubernetes Manifests

When working with Kubernetes manifests, especially for cloud-native testing infrastructure, following these best practices will help ensure reliable deployments:

• ‍Use version control for all your manifest files. This allows you to track changes, roll back when needed, and maintain consistency across environments.‍
• Implement resource limits and requests to ensure your testing workloads don't consume excessive cluster resources and can scale appropriately.‍
• Add meaningful labels and annotations to help organize and manage your Kubernetes objects, making them easier to identify and troubleshoot.‍
• Use namespaces to isolate different environments (development, staging, production) and different types of testing workloads.‍
• Validate manifests before deployment using tools like kubectl dry-run or dedicated validation tools to catch errors early.

Kubernetes Manifests for Testing Infrastructure

When deploying testing infrastructure with platforms like Testkube, your manifests need to account for specific testing requirements:

• ‍Test execution environments often need different resource allocations than production workloads, as they may require more CPU or memory for intensive testing scenarios.‍
• Network policies become crucial when running security tests or testing network connectivity between services.‍
• Storage requirements may vary depending on whether you're running database tests, file upload tests, or need to persist test artifacts.‍
• Environment variables and secrets management is critical for tests that need to connect to external services or databases.

Troubleshooting Kubernetes Manifest Issues

Beyond the common formatting errors mentioned above, here are additional troubleshooting tips:

• ‍Check resource quotas if your pods aren't starting. Sometimes the issue isn't with your manifest syntax but with cluster resource limitations.‍
• Verify image pull policies and registry access. Many deployment failures stem from inability to pull container images.‍
• Review security contexts and pod security policies, especially in production clusters with strict security requirements.‍
• Monitor pod logs and events using kubectl describe and kubectl logs to understand why deployments might be failing.

Frequently Asked Questions