fix: Use TARGETARCH for multi-platform builds

[lexfrei]

Summary

Enable ARM64 and other architecture support by using Docker's automatic TARGETARCH variable instead of hardcoded GOARCH=amd64.

Problem

The current Dockerfile hardcodes ARG GOARCH=amd64, which prevents building images for other architectures like arm64 using docker buildx build --platform linux/arm64.

Solution

• Use TARGETARCH which is automatically set by Docker buildx during multi-platform builds
• Fall back to amd64 for backward compatibility with non-buildx builds

Changes

# Before
ARG GOARCH=amd64

# After
ARG TARGETARCH
ARG GOARCH=${TARGETARCH:-amd64}

Testing

Build for multiple platforms:

docker buildx build --platform linux/amd64,linux/arm64 -t kilo:test .

Related

• feat: ARM64 support for Generic Kubernetes (non-Talos) cozystack#1961

Summary by CodeRabbit

• Chores
  • Docker build updated to detect and use the target CPU architecture across build stages, including downloads of platform-specific components. This improves multi‑architecture build support and broadens platform compatibility without changing runtime behavior.

[gemini-code-assist]

Summary of Changes

Hello @lexfrei, 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 significantly enhances the Docker image build process by introducing dynamic architecture detection. It resolves the limitation of hardcoded amd64 builds, allowing for seamless multi-platform image creation, particularly for ARM64, while maintaining compatibility with existing build workflows.

Highlights

• Multi-platform build support: Enabled support for building Docker images across various architectures, including ARM64, by dynamically determining the target architecture.
• Flexible architecture detection: Replaced the static GOARCH=amd64 argument with TARGETARCH, which is automatically provided by Docker buildx during multi-platform builds.
• Backward compatibility: Ensured that builds not using buildx or TARGETARCH will gracefully fall back to amd64 as the default architecture.

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Changelog

• Dockerfile
  • Replaced ARG GOARCH=amd64 with ARG TARGETARCH and ARG GOARCH=${TARGETARCH:-amd64}.
  • Added a comment explaining the purpose of TARGETARCH.

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[coderabbitai]

📝 Walkthrough

Walkthrough

The Dockerfile now accepts a TARGETARCH build argument and sets GOARCH dynamically to ${TARGETARCH:-amd64} in both stages, replacing the prior hardcoded GOARCH=amd64. The CNI plugins download URL is updated to use the derived GOARCH value.

Changes

Cohort / File(s)	Summary
Multi-architecture Build Dockerfile	Adds ARG TARGETARCH and replaces hardcoded GOARCH=amd64 with GOARCH=${TARGETARCH:-amd64} in both build stages; CNI plugins URL now references the dynamic GOARCH variable.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~8 minutes

Poem

🐇 I hopped into the Docker tree,
TARGETARCH whispered back to me,
GOARCH dances, no more static tune,
Builds for ARM, amd64 — a happy rune,
One Dockerfile, under the moon. 🌙

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and specifically describes the main change: introducing TARGETARCH for multi-platform Docker builds instead of hardcoded GOARCH.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

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[gemini-code-assist]

Code Review

This pull request aims to enable multi-platform builds by using Docker's TARGETARCH variable. The change correctly updates the first stage of the Dockerfile to use TARGETARCH for downloading CNI plugins. However, the change is incomplete as the second stage of the Dockerfile is not updated, which will cause buildx builds to fail. I've left a specific comment with details on how to fix this.

[gemini-code-assist]

This is a good change for supporting multi-platform builds in the cni stage. However, the second stage of this Dockerfile also depends on the architecture but has not been updated. The ARG GOARCH on line 12 is declared without a value, so when using buildx it will be empty. This will cause the COPY commands on lines 20-21 to fail.

To fully enable multi-platform builds as intended, you should apply the same pattern to the second build stage by adding ARG TARGETARCH and setting ARG GOARCH=${TARGETARCH:-amd64}.

[lexfrei]

Good catch, fixed in 71eea82 — applied the same TARGETARCH pattern to the runtime stage.

[coderabbitai]

Caution

Some comments are outside the diff and can’t be posted inline due to platform limitations.

⚠️ Outside diff range comments (1)

Dockerfile (1)

12-12: ⚠️ Potential issue | 🔴 Critical

Bug: GOARCH will be empty in stage 2 during multi-platform builds.

Docker ARG values don't carry across stage boundaries. Since GOARCH is only derived from TARGETARCH in stage 1, the second stage's ARG GOARCH (line 12) will resolve to an empty string during buildx builds—causing lines 20–21 to expand to bin/linux//kg and bin/linux//kgctl.

You need to re-declare TARGETARCH and derive GOARCH in stage 2 as well:

Proposed fix

 FROM $FROM
-ARG GOARCH
+ARG TARGETARCH
+ARG GOARCH=${TARGETARCH:-amd64}
 ARG ALPINE_VERSION=v3.20

[lexfrei]

Fixed the runtime stage issue flagged by @coderabbitai in 71eea82 — ARG GOARCH now uses ${TARGETARCH:-amd64} in both stages.

[coderabbitai]

Tip

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🧩 Analysis chain

🏁 Script executed:

#!/bin/bash
# Read the Dockerfile to verify the fix in both stages
cat Dockerfile

Length of output: 1194

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@lexfrei Thank you for the fix! I can confirm that the Dockerfile now correctly declares both ARG TARGETARCH and ARG GOARCH=${TARGETARCH:-amd64} in both the builder stage (lines 3-4) and the runtime stage (lines 11-12). This ensures that multi-platform builds will work correctly across both stages, with the proper fallback to amd64 for backward compatibility. Great work! 🎉

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[kvaps]

Lgtm