Migrate kubectl exec to WebSockets from SPDY

[andyvandy]

( clone of PR loft-sh#1980 )

I've added websocket support since I want to setup a capsule kube api proxy which was dropping connections due to lack of SPDY support.

Per KEP-4006, I prioritize trying WebSockets first given Websockets have been the default for 4 versions now and will be the standard going forward. I used NewFallbackExecutor as suggested in the KEP to avoid breaking existing use cases.

This follows the implementation used by kubectl: https://github.com/kubernetes/kubectl/blob/8144b746a47f142759a073a46f581de92b1886aa/pkg/cmd/exec/exec.go#L146-L166

I've built this locally and have been using it successfully for myself and a few others. Disclosure: this fix was found with the assistance of claude/copilot.

Summary by CodeRabbit

• Bug Fixes
  • Improved Kubernetes command execution reliability by preferring a modern connection method and adding smarter fallback selection when upgrade or proxy errors occur, resulting in more stable and compatible remote command sessions across diverse cluster environments.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 19752af9-df44-4fc4-817f-f3415cf2c727

📥 Commits

Reviewing files that changed from the base of the PR and between 4add125 and 2b0cedf.

📒 Files selected for processing (1)

• pkg/driver/kubernetes/client.go

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📝 Walkthrough

Walkthrough

Client.Exec now attempts a WebSocket-based Kubernetes exec first and constructs an SPDY executor as a fallback, wrapped with remotecommand.NewFallbackExecutor that uses httpstream.IsUpgradeFailure and httpstream.IsHTTPSProxyError to decide when to fall back.

Changes

Kubernetes WebSocket Executor Fallback

Layer / File(s)	Summary
WebSocket-first exec with SPDY fallback pkg/driver/kubernetes/client.go	Adds the httpstream import and changes Client.Exec to build a WebSocket executor as primary and an SPDY executor as fallback, wrapped by remotecommand.NewFallbackExecutor and using httpstream.IsUpgradeFailure / httpstream.IsHTTPSProxyError to trigger the fallback.

Estimated code review effort

🎯 4 (Complex) | ⏱️ ~45 minutes

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The PR title 'Migrate kubectl exec to WebSockets from SPDY' directly and accurately describes the main technical change in the changeset—updating the Kubernetes client to use WebSocket-based execution instead of SPDY.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@pkg/driver/kubernetes/client.go`:
- Line 128: The fallback predicate passed to remotecommand.NewFallbackExecutor
currently only uses httpstream.IsUpgradeFailure; update the call in the
remotecommand.NewFallbackExecutor invocation (the websocketExec, spdyExec
creation site) to use a combined predicate that checks both
httpstream.IsUpgradeFailure and httpstream.IsHTTPSProxyError (i.e., call
NewFallbackExecutor with a predicate that returns true if either
IsUpgradeFailure or IsHTTPSProxyError matches) so HTTPS-proxy dial failures will
trigger the SPDY fallback just like kubectl.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 635de3ff-cde9-4e2d-a7ba-7614d78d4fa7

📥 Commits

Reviewing files that changed from the base of the PR and between 95d2230 and 4add125.

📒 Files selected for processing (1)

• pkg/driver/kubernetes/client.go

[skevetter]

Happy to get this merged in once the failing jobs are fixed.