feat: disable write back informer by default

[eduardodbr]

Motivation

We’ve seen several cases of unexpected behavior that appear to be caused by the write-back mechanism, and Kubernetes docs (and maintainers kubernetes-sigs/controller-runtime#1622) recommend avoiding writes to the informer store. Although turning it off may increase the frequency of 409 Conflict errors, it should help reduce unpredictable controller behavior.

Modifications

Verification

Documentation

[eduardodbr]

/retest

[Copilot]

Pull request overview

This PR changes the default behavior of the INFORMER_WRITE_BACK environment variable from true to false to address unexpected controller behavior. The change aligns with Kubernetes best practices that recommend avoiding writes to the informer store, though it may result in more 409 Conflict errors.

Key Changes:

• Modified the switch statement logic in operator.go to make the empty string case default to "false" behavior instead of "true"
• Updated documentation to reflect the new default value of false
• Added feature documentation explaining the rationale for this change

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
workflow/controller/operator.go	Swapped the case statements to make empty string default to the "false" behavior (no write-back to informer cache) instead of "true"
docs/environment-variables.md	Updated the default value for INFORMER_WRITE_BACK from true to false in the environment variables table
.features/pending/disable-write-back-informer.md	Added feature documentation explaining the motivation for disabling write-back informer by default

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[Copilot]

The comment is now grammatically incomplete after the partial removal. It starts with lowercase "this does not reduce errors" which makes it unclear what "this" refers to. Consider revising to: "Writing back to the informer does not reduce errors, but does reduce conflicts and therefore we log fewer warning messages."

Suggested change

	// this does not reduce errors, but does reduce
	// conflicts and therefore we log fewer warning messages.
	// Writing back to the informer does not reduce errors, but does reduce conflicts and therefore we log fewer warning messages.

[Copilot]

The comment on line 808 starts with lowercase and lacks proper sentence structure. Consider revising to: "No longer write back to informer cache as default (as per v4.0)."

Suggested change

	// no longer write back to informer cache as default (as per v4.0)
	// No longer write back to informer cache as default (as per v4.0).

[Copilot]

There's an extra trailing space after false in the default value column. This should be removed for consistency with other entries in the table.

Suggested change

	| `INFORMER_WRITE_BACK` | `bool` | `false` | Whether to write back to informer instead of catching up. |
	| `INFORMER_WRITE_BACK` | `bool` | `false` | Whether to write back to informer instead of catching up. |