feat: Update Flagd container injection to native Kubernetes sidecar

[Y0sh1dk]

This PR

Fixes #806 by updating the flagd container injection to inject as a sidecar

Related Issues

Fixes #806

Notes

• This is a breaking change to the operator for Kubernetes clusters older than v1.29. See: https://kubernetes.io/docs/tutorials/configuration/pod-sidecar-containers/#adopting-built-in-sidecar-containers

How to test

Minimal scenario to test documented in #806

[gemini-code-assist]

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request refactors the flagd container injection logic within the OpenFeature operator to leverage native Kubernetes sidecar containers, addressing a known issue. This change aligns the operator with modern Kubernetes practices for managing auxiliary containers, improving the lifecycle management of flagd instances. It's important to note that this update introduces a breaking change for older Kubernetes versions (pre-v1.29) that do not support built-in sidecar containers.

Highlights

• Native Kubernetes Sidecar Injection: Updated the flagd container injection mechanism to utilize native Kubernetes sidecar containers, aligning with modern Kubernetes practices for auxiliary container management.
• Flagd Container Restart Policy: Introduced a RestartPolicy of Always for the injected flagd sidecar container to ensure continuous operation.
• Injection Logic Refinement: Modified the addFlagdContainer logic to target PodSpec.InitContainers instead of PodSpec.Containers for flagd injection.
• Breaking Change Notification: Noted that this change is breaking for Kubernetes clusters older than v1.29, as they do not support built-in sidecar containers.

Changelog

• internal/common/flagdinjector/flagdinjector.go
  • Imported k8s.io/utils/ptr for pointer utilities.
  • Added RestartPolicy: ptr.To(corev1.ContainerRestartPolicyAlways) to the generated flagd container.
  • Modified addFlagdContainer to append and update spec.InitContainers instead of spec.Containers.
• internal/common/flagdinjector/flagdinjector_test.go
  • Imported corev1 and k8s.io/utils/ptr.
  • Removed several blank lines for cleaner code.
  • Updated calls to generatePod to include a new initContainers parameter, passing nil where appropriate.
  • Modified assertions to check expectedPod.Spec.InitContainers[0] instead of expectedPod.Spec.Containers[1].
  • Updated the generatePod function signature and implementation to accept and utilize an initContainers slice.
  • Adjusted getExpectedPod to define the flagd container within InitContainers instead of Containers, and added the RestartPolicy.

Activity

• No human activity (comments, reviews, etc.) has been recorded on this pull request yet.

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[gemini-code-assist]

Code Review

This pull request updates the flagd container injection to use native Kubernetes sidecar containers, which is a great improvement for clusters that support this feature (v1.29+). The changes correctly modify the injection logic to place the flagd container into initContainers with restartPolicy: Always. The tests have been updated accordingly to validate the new behavior. The implementation is solid. I've left one minor comment regarding import consistency in a test file.

[gemini-code-assist]

The package k8s.io/api/core/v1 is imported twice with different aliases (corev1 and v1). This is confusing and should be consolidated. It's recommended to use a single alias, corev1 is the standard convention, and replace all occurrences of v1. with corev1. throughout the file for consistency.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 72.34%. Comparing base (499661e) to head (ff9329a).
⚠️ Report is 78 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff             @@
##             main     #807       +/-   ##
===========================================
- Coverage   86.51%   72.34%   -14.17%     
===========================================
  Files          19       30       +11     
  Lines        1587     1924      +337     
===========================================
+ Hits         1373     1392       +19     
- Misses        173      484      +311     
- Partials       41       48        +7     

Files with missing lines	Coverage Δ
internal/common/flagdinjector/flagdinjector.go	88.77% <100.00%> (ø)

... and 25 files with indirect coverage changes

Flag	Coverage Δ
unit-tests	72.34% <100.00%> (∅)

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