Kubernetes Deprecated APIs: A Practical Guide to Management

Managing a Kubernetes cluster often involves juggling resource allocation, security, and updates. One tricky aspect is handling Kubernetes deprecated APIs. Knowing which APIs are outdated, where they're used, and how to migrate is crucial for avoiding disruptions and vulnerabilities. This post offers a practical guide to identifying and managing these deprecated Kubernetes APIs, covering manual and automated solutions. We'll also explore how Plural simplifies this process, providing better visibility and control for smoother Kubernetes deployments.

Running outdated Kubernetes versions puts your application at risk of experiencing downtime, like a site-wide outage experienced by Reddit in 2023. While that was a worst-case scenario, you can’t afford anything but your business application that makes your company money can’t afford to be down for even one minute.

In this post, we’ll highlight how you would detect APIs in your cluster without Plural and explore how Plural automates this process for you in a single pane of glass.

Understanding the Kubernetes API

The Kubernetes API serves as an interface to interact with a Kubernetes cluster. It allows users to query and manipulate Kubernetes objects like pods, namespaces, and deployments. These APIs can be accessed through tools such as kubectl, via the REST API directly, or using client libraries.

Even if upgrading doesn’t result in a full-out outage, tiny differences in Kubernetes APIs can frustrate developers hunting down the underlying problem. While figuring out Kubernetes API versions for one cluster isn’t bad, it increases in complexity and time required when identifying specific API versions for a large fleet of clusters spread out across multiple teams utilizing various cloud, on-prem, and edge environments.

Key Takeaways

• Deprecated Kubernetes APIs can cause application downtime. Regularly review the Kubernetes Deprecation Guide and test your applications to avoid disruptions during upgrades.
• Manually tracking deprecated APIs is difficult. Tools like kubectl convert and Kubent are helpful, but managing deprecations at scale requires a more comprehensive solution.
• Plural automates deprecated API management. Connecting Plural to your Git repositories allows for automatic scanning and identification of deprecated resources, simplifying remediation and Kubernetes upgrades.

Why Kubernetes APIs Get Deprecated

Kubernetes is a large, complex system with many moving parts and contributors. Features naturally evolve, and sometimes, older components need to be removed to make way for new improvements. This isn’t limited to just APIs—flags, entire features, and other elements can also be deprecated. Think of it like renovating a house: sometimes you have to tear down a wall to make room for something better.

The Kubernetes Deprecation Policy

To avoid disrupting users and their applications, Kubernetes follows a deprecation policy. This policy outlines the process for removing features, giving developers time to adapt and migrate to newer versions. It ensures a smoother transition and minimizes the risk of breaking changes. This is crucial for maintaining the stability and reliability of Kubernetes clusters in production environments.

Deprecation Periods

Different API stability levels have different deprecation timelines. Generally available (GA) APIs have the longest deprecation period within a major Kubernetes version, providing ample time for migration. Beta APIs have a shorter timeframe—typically nine months or three minor releases, whichever is longer. Alpha APIs, being experimental, can be removed at any time. This tiered approach allows for flexibility while ensuring stability for production-ready features. For specific details on deprecation timelines, refer to the official Kubernetes documentation.

Data Conversion Requirements

A key aspect of the deprecation policy is data conversion. When migrating between API versions, data must be convertible without any loss of information. This ensures that your existing data remains intact and usable even after upgrading to a newer Kubernetes version. This focus on backward compatibility helps maintain data integrity throughout the evolution of the platform. This is particularly important for stateful applications and ensures a seamless transition during upgrades.

Stability Level Considerations

Kubernetes APIs are categorized by stability levels: alpha, beta, and GA. This classification indicates the maturity and stability of each API. Only GA versions are guaranteed long-term support and adhere to the deprecation policy. Understanding these levels helps you make informed decisions about which APIs to use in your applications and plan for potential upgrades or migrations. Relying on stable GA APIs minimizes the risk of encountering breaking changes.

Feature Gate Deprecation

Kubernetes uses feature gates to enable or disable experimental features. These feature gates also have their own deprecation rules, tied to the feature's lifecycle. As a feature moves from alpha to beta and eventually to GA, the corresponding feature gate may also be deprecated and eventually removed. This allows for controlled experimentation and gradual rollout of new features. Staying informed about feature gate deprecations is essential for maintaining a stable and predictable Kubernetes environment.

Metric Deprecation

Even metrics are subject to deprecation in Kubernetes. Similar to APIs, metrics have different deprecation periods based on their stability level. Stable metrics have the longest deprecation period (12 months or four releases), beta metrics have a shorter period (eight months or two releases), and alpha metrics can be removed immediately. This ensures that monitoring and observability tools can adapt to changes in the metrics landscape. Keeping track of metric deprecations is crucial for maintaining accurate monitoring and alerting systems.

Finding Deprecated Kubernetes APIs Without Plural

Although Kubernetes provides official documentation to examine deprecated or removed APIs, identifying resources in your cluster utilizing those APIs can be quite challenging.

Kubernetes abides by a stringent API versioning protocol, resulting in multiple deprecations of v1beta1 and v2beta1 APIs across several releases. Their policy states Beta API versions are mandated to receive support for a minimum of 9 months or 3 releases (whichever is longer) after deprecation, after which may be subject to removal.

In cases where APIs have been deprecated and are still actively employed by workloads, tools, or other components interfacing with clusters, disruptions may occur. Hence, users and administrators must conduct a thorough assessment of their cluster to identify any APIs in use slated for removal, and subsequently migrate affected components to leverage the appropriate new API version.

An example is the APIVersion extensions/v1beta1 of the Ingress Resource, which was removed in Kubernetes version v1.22. Attempting to use such a removed API version in your configuration would result in an error message:

 Error: UPGRADE FAILED: current release manifest contains removed kubernetes api(s) for this kubernetes version and it is therefore unable to build the kubernetes objects for performing the diff. error from kubernetes: unable to recognize "": no matches for kind "Ingress" in version "extensions/v1beta1"

You can also review all supported API groups along with their versions through official documentation or by using kubectl command-line tool's api-versions command:‌

kubectl api-versions
admissionregistration.k8s.io/v1
admissionregistration.k8s.io/v1beta1
apiextensions.k8s.io/v1
apiextensions.k8s.io/v1beta1
apiregistration.k8s.io/v1
apiregistration.k8s.io/v1beta1
apps/v1

However, simply listing your Kubernetes resources using kubectl commands may yield inaccurate API version information, as explained in this issue.

Still, identifying deprecated versions of Kubernetes APIs is a laborious and error-prone task, requiring manual inspection of all manifests. This process becomes even more cumbersome – or even impossible – when multiple teams deploy to a cluster without a centralized manifest repository.

Using the Kubernetes Deprecation Guide

The Kubernetes Deprecation Guide is your primary resource for navigating API changes. As Kubernetes evolves, older APIs are deprecated and eventually removed. The guide helps you understand these changes and how to adapt your deployments. It’s a living document, updated with each Kubernetes release, so make sure you’re referencing the version relevant to your cluster.

Specific Deprecated APIs and Their Replacements

The guide lists specific deprecated APIs for various Kubernetes releases. For each deprecated API, it provides the recommended replacement version. This information is crucial for ensuring your applications remain compatible with newer Kubernetes versions. For example, the extensions/v1beta1 API version of Ingress, deprecated in Kubernetes 1.19, should be replaced with networking.k8s.io/v1. Knowing these specific replacements allows for targeted updates and reduces the chance of introducing errors.

Notable Changes in API Versions

Beyond just listing replacements, the Deprecation Guide often highlights notable changes between API versions. These changes might include new features, altered functionalities, or structural modifications. For instance, a field might become mandatory, or a default value could change. Understanding these nuances is essential for a smooth transition and prevents unexpected behavior after an upgrade. Pay close attention to these details to avoid post-upgrade surprises.

Leveraging the kubectl convert Tool

The kubectl convert tool can automatically update your YAML configuration files to newer API versions. This automation simplifies the migration process, especially for large, complex deployments. It can save you significant time and effort compared to manual updates.

Installation and Usage

While kubectl is a standard tool, the convert plugin might not be installed by default in older kubectl versions. You can install it using kubectl apply -f https://github.com/kubernetes-sigs/kubectl-plugins/releases/download/v0.0.28/kubectl-convert_0.0.28-linux-amd64.yaml (adjust the link for your operating system). After installation, using the tool is straightforward: kubectl convert -f <your-yaml-file>. This command attempts to update the API versions in your YAML file to the latest supported versions. You can also specify a target API version using the --output-version flag.

Limitations and Manual Review

While kubectl convert is helpful, it’s not perfect. The automatic conversion might use suboptimal default settings or miss certain edge cases. Always review the converted YAML files manually to ensure the changes are accurate and align with your application’s requirements. Testing the converted configurations in a staging environment is highly recommended before deploying to production. This extra step can prevent unexpected issues in your live environment.

Using the Built-in Warning System

Kubernetes (v1.19 and later) includes a built-in warning system that flags deprecated API usage. Enable these warnings to proactively identify areas in your deployments that require updates. This early detection helps you address deprecations before they impact your application. Refer to the Kubernetes documentation for how to enable these warnings in your specific environment.

Proactive Testing with Deprecated APIs Disabled

To thoroughly test your application’s resilience to API changes, try running your cluster with deprecated APIs disabled. This simulates the environment of a future Kubernetes upgrade and reveals any compatibility problems early on. This proactive approach minimizes the risk of disruptions during actual upgrades and allows you to address issues in a controlled manner.

Employing Kubent (Kube-No-Trouble)

Kubent (Kube-No-Trouble) is a valuable tool for scanning your cluster for deprecated APIs. It provides a comprehensive report detailing which resources are using outdated APIs, facilitating targeted updates and remediation. This can be particularly helpful in large, complex clusters.

Installation and Benefits

Kubent is easy to install using standard package managers like brew or by downloading the binary directly from the project's GitHub repository. It offers a clear and concise overview of deprecated API usage within your cluster, making it easier to prioritize and address these issues. This proactive approach simplifies the upgrade process and reduces the risk of encountering unexpected problems. Kubent can also help you identify potential security vulnerabilities associated with outdated APIs.

Understanding the Nuances of kubectl api-versions

The kubectl api-versions command lists all supported API versions in your cluster. While this command doesn't directly identify *deprecated* APIs, it’s useful for understanding the available versions and planning your migration strategy. Combine this information with the Kubernetes Deprecation Guide to make informed decisions about API updates. This command can also be helpful for troubleshooting compatibility issues between different Kubernetes components.

How to Find Deprecated Kubernetes APIs With Plural

Plural offers a comprehensive analysis of source code deployed to your Kubernetes clusters by scanning existing Git repositories. Our platform automatically surfaces deprecated resources detected on clusters and links the location in Github for review. To access these features you’ll need to sign in to your plural account and navigate to the Plural console.

Deprecations will surface at the cluster level in the "Status" column of the Clusters table. If the cluster was deployed via Plural, a button to upgrade the cluster will appear. If you deployed the cluster yourself Plural will surface a notification to upgrade the cluster externally to the latest version.

To see deprecations relevant to a specific service, navigate to the Service details page. You'll see a notification to review any changes that need to be made:

So you can triage a ticket to the appropriate service owner to get it fixed before you hit that next upgrade.

On top of this, Plural will immediately identify non-compatible Kubernetes add-ons that make Kubernetes upgrades challenging. Our platform will surface the compatible Kubernetes versions based on their documentation.

You can also see the full version history for those add-ons as well. One of the main benefits of this approach is it removes a lot of the risks from upgrading and this helps engineers who are not as familiar with the Kubernetes ecosystem be able to own a Kubernetes upgrade instead of a very seasoned senior engineer.

Integrating Deprecation Checks into Your Workflow

Proactively checking for deprecated Kubernetes APIs should be a standard part of your workflow. Kubernetes follows a strict deprecation policy, giving you time to migrate before an older API version is removed. However, manually tracking these deprecations across your services and clusters is a significant undertaking. Identifying deprecated versions requires meticulous inspection of your manifests, a process that quickly becomes unwieldy with multiple teams and deployments.

Without a centralized system, keeping track of which APIs are nearing their end-of-life and ensuring all your deployments are using supported versions becomes a constant challenge. This manual process is not only time-consuming but also prone to errors. Overlooking a single deprecated API can lead to disruptions and downtime when you upgrade your cluster, as highlighted in the Kubernetes Deprecation Guide. This reactive approach puts your applications at risk and creates unnecessary stress for your team.

Automating Remediation with Plural

Plural simplifies the entire deprecation management process. By connecting Plural to your Git repositories, our platform automatically scans your source code and identifies any deprecated resources deployed on your clusters. We don't just flag the deprecations; we link them directly to the relevant location in your GitHub repository, making it easy to pinpoint the code that needs updating. This eliminates the need for manual inspection and significantly reduces the risk of overlooking critical deprecations. For more details, read our blog post on managing deprecated Kubernetes APIs with Plural.

Plural provides clear visibility into the deprecation status of your clusters and services. At the cluster level, the "Status" column in the Clusters table clearly indicates any deprecations. For clusters deployed and managed through Plural, you can upgrade with a single click. If you manage your clusters externally, Plural still provides clear notifications prompting you to upgrade to a supported version. At the service level, the Service details page displays specific deprecations, allowing you to assign remediation tasks to the appropriate team. This proactive approach ensures that you're always aware of potential issues and can address them before they impact your applications.

Beyond API deprecations, Plural also simplifies Kubernetes upgrades by identifying incompatible add-ons. Our platform automatically surfaces compatible Kubernetes versions based on the add-on documentation, providing a clear upgrade path and reducing the risk of unexpected issues. This feature empowers engineers of all levels to confidently manage Kubernetes upgrades, freeing up senior engineers to focus on more strategic tasks. By automating these critical processes, Plural helps you maintain a healthy and stable Kubernetes environment, minimizing disruptions and maximizing uptime.

Managing Your Kubernetes Fleet with Plural

Currently, the barrier to entry for working with Kubernetes is high and slows down fast-moving teams' adoption of Kubernetes at scale. Plural allows any engineer to easily manage their Kubernetes ecosystem anywhere - securely and at scale -  in a single pane of glass regardless of expertise.

Plural is a self-hosted Kubernetes fleet management platform that provides a single pane of glass, removing the complexity of managing Kubernetes clusters at scale. With Plural, engineering teams can gain visibility, automation, governance, and security capabilities in an easily adaptable platform to manage the lifecycle of Kubernetes clusters across public clouds such as AWS, Azure, and GCP as well as on-prem and remote/edge locations.

With Plural, engineering teams can do the following:

• Gain multi-cluster visibility into your entire cluster fleet across various environments. With Plural, your engineers get self-service access to Kubernetes clusters and automated cluster lifecycle management using proven templates with guardrails included.
• Manage Kubernetes clusters and add-on upgrades in a single, intuitive interface and confidently know that upgrading a Kubernetes version won’t break anything downstream. Plural will help you with upgrading the control plane, Kubernetes add-ons, and your services. With Plural, you’ll be made aware if you have a compatible version of your add-ons for the version of Kubernetes you are upgrading.
• Share the responsibility of managing Kubernetes tasks with a broader subset of your engineers, including those without prior Kubernetes experience. Top-tier Kubernetes talent is costly and hard to attain. Managing infrastructure shouldn’t be challenging and pricey, and your most skilled engineers should focus on building out awesome product features to drive business value. With Plural, your team can create standard workflows to automate time-tedious and challenging tasks of configuring, and provisioning clusters across fleets in one patch rather than following the manual, error-prone process today that makes managing Kubernetes clusters challenging.

To learn more about Plural’s self-hosted fleet Kubernetes fleet management platform sign up for a custom product demo to learn more.

Related Articles

• Understanding Deprecated Kubernetes APIs and Their Significance
• How to Detect Deprecated Kubernetes APIs with Plural
• Kubernetes API: Your Guide to Cluster Management
• Best Kubernetes Management Tools: Simplify Cluster Operations
• Kubernetes Cluster Upgrade Cycles: A Practical Guide

Frequently Asked Questions

Why should I care about deprecated Kubernetes APIs? Using deprecated APIs can lead to application instability and potential downtime when you upgrade your Kubernetes cluster. Newer Kubernetes versions may remove support for these older APIs, causing your applications to malfunction or fail entirely. Staying on top of API deprecations ensures a smoother upgrade process and keeps your applications running reliably.

How often are Kubernetes APIs deprecated? Kubernetes follows a regular release cycle, typically every three months. With each new release, some APIs may be deprecated, while others are introduced. The deprecation cycle allows for a transition period, usually nine months or three releases for beta APIs, giving you time to update your applications. Generally available (GA) APIs have longer deprecation periods. It's best to consult the official Kubernetes Deprecation Guide for specific timelines.

What's the easiest way to find and update deprecated APIs in my deployments? Manually tracking deprecated APIs across numerous deployments is complex and error-prone. Tools like Plural automate this process by scanning your configurations and highlighting deprecated APIs, linking them directly to your code repository for easy updates. This proactive approach simplifies the entire process and reduces the risk of overlooking critical deprecations.

How can I test my applications for compatibility with future Kubernetes versions? One effective strategy is to run your cluster with deprecated APIs disabled. This simulates the environment of a future upgrade and helps identify any compatibility issues early on. You can also use tools like kubectl convert to update your YAML files to newer API versions, but always review the converted files manually to ensure accuracy.

What are the risks of not addressing deprecated APIs? Ignoring deprecated APIs can lead to significant problems during Kubernetes upgrades. Your applications might experience unexpected behavior, errors, or even complete failure. This can result in downtime, impacting your users and business operations. Addressing deprecations proactively ensures a smoother upgrade process and minimizes the risk of disruptions.