WIP: structured error, funcr.PseudoStruct by pohly · Pull Request #361 · kubernetes/klog

pohly · 2022-12-06T18:43:50Z

What this PR does / why we need it:

Nicer formatting of error details.

Which issue(s) this PR fixes:
Fixes #357

Special notes for your reviewer:

This is a variant of the idea with the existing funcr.PseudoType.

Release note:

MarshalLog may return funcr.PseudoType (aka funcr/types.PseudoType) and those key/value pairs then will get logged like a struct with those fields. When an error implements MarshalLog, it gets logged both as `err=<Error()>` and as `errDetails=<MarshalLog()>`.

dashpole · 2022-12-15T17:50:06Z

/assign @harshanarayana
/triage accepted

k8s-triage-robot · 2023-05-04T09:17:58Z

The Kubernetes project currently lacks enough contributors to adequately respond to all PRs.

This bot triages PRs according to the following rules:

After 90d of inactivity, lifecycle/stale is applied
After 30d of inactivity since lifecycle/stale was applied, lifecycle/rotten is applied
After 30d of inactivity since lifecycle/rotten was applied, the PR is closed

You can:

Mark this PR as fresh with /remove-lifecycle stale
Close this PR with /close
Offer to help out with Issue Triage

Please send feedback to sig-contributor-experience at kubernetes/community.

/lifecycle stale

k8s-triage-robot · 2023-06-03T09:45:39Z

The Kubernetes project currently lacks enough active contributors to adequately respond to all PRs.

This bot triages PRs according to the following rules:

After 90d of inactivity, lifecycle/stale is applied
After 30d of inactivity since lifecycle/stale was applied, lifecycle/rotten is applied
After 30d of inactivity since lifecycle/rotten was applied, the PR is closed

You can:

Mark this PR as fresh with /remove-lifecycle rotten
Close this PR with /close
Offer to help out with Issue Triage

Please send feedback to sig-contributor-experience at kubernetes/community.

/lifecycle rotten

pohly · 2023-06-03T19:50:17Z

/remove-lifecycle rotten

Waiting for slog in Go 1.21.

pohly · 2024-01-10T08:42:10Z

We could do this now, but I'd like to hear from @tallclair first whether this feature is really needed and going to be used.

k8s-triage-robot · 2024-04-09T09:29:02Z

The Kubernetes project currently lacks enough contributors to adequately respond to all PRs.

This bot triages PRs according to the following rules:

After 90d of inactivity, lifecycle/stale is applied
After 30d of inactivity since lifecycle/stale was applied, lifecycle/rotten is applied
After 30d of inactivity since lifecycle/rotten was applied, the PR is closed

You can:

Mark this PR as fresh with /remove-lifecycle stale
Close this PR with /close
Offer to help out with Issue Triage

Please send feedback to sig-contributor-experience at kubernetes/community.

/lifecycle stale

k8s-triage-robot · 2024-05-09T10:08:29Z

The Kubernetes project currently lacks enough active contributors to adequately respond to all PRs.

This bot triages PRs according to the following rules:

After 90d of inactivity, lifecycle/stale is applied
After 30d of inactivity since lifecycle/stale was applied, lifecycle/rotten is applied
After 30d of inactivity since lifecycle/rotten was applied, the PR is closed

You can:

Mark this PR as fresh with /remove-lifecycle rotten
Close this PR with /close
Offer to help out with Issue Triage

Please send feedback to sig-contributor-experience at kubernetes/community.

/lifecycle rotten

k8s-triage-robot · 2024-06-08T10:53:33Z

The Kubernetes project currently lacks enough active contributors to adequately respond to all issues and PRs.

This bot triages PRs according to the following rules:

After 90d of inactivity, lifecycle/stale is applied
After 30d of inactivity since lifecycle/stale was applied, lifecycle/rotten is applied
After 30d of inactivity since lifecycle/rotten was applied, the PR is closed

You can:

Reopen this PR with /reopen
Mark this PR as fresh with /remove-lifecycle rotten
Offer to help out with Issue Triage

Please send feedback to sig-contributor-experience at kubernetes/community.

/close

k8s-ci-robot · 2024-06-08T10:53:38Z

@k8s-triage-robot: Closed this PR.

Details

In response to this:

The Kubernetes project currently lacks enough active contributors to adequately respond to all issues and PRs.

This bot triages PRs according to the following rules:

After 90d of inactivity, lifecycle/stale is applied

After 30d of inactivity since lifecycle/stale was applied, lifecycle/rotten is applied

After 30d of inactivity since lifecycle/rotten was applied, the PR is closed

You can:

Reopen this PR with /reopen

Mark this PR as fresh with /remove-lifecycle rotten

Offer to help out with Issue Triage

Please send feedback to sig-contributor-experience at kubernetes/community.

/close

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.

This special type can be used as value in WithValues/Info/Error or as result of MarshalLog. It gets rendered like a struct, with curly brackets around the content. While at it, the import aliases get updated: - link to docs - add PseudoStruct (new) - add Marshaler (an omission that currently forces several Kubernetes files to reference logr directly)

pohly · 2026-01-08T12:53:18Z

/reopen

Still relevant for #357

k8s-ci-robot · 2026-01-08T12:53:26Z

@pohly: Reopened this PR.

Details

In response to this:

/reopen

Still relevant for #357

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.

k8s-ci-robot · 2026-01-08T12:53:32Z

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: pohly

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Details

Needs approval from an approver in each of these files:

~~OWNERS~~ [pohly]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

pohly · 2026-01-23T12:13:20Z

/remove-lifecycle rotten

Updated based on the discussion in go-logr/zapr#56.

/hold

The zapr PR should get merged first, then used in this PR for the examples, which will depend on updating test/zapr.go. Currently it documents the behavior without support in zapr for ErrorDetails.

/assign @tallclair

You asked for this in #357.

pohly · 2026-01-23T12:15:09Z

structured_error.go

+// Other backends might not support this, so all relevant information
+// should be in the error string.
+type ErrorDetailer interface {
+	ErrorDetails() any


This could become a type alias for logr.ErrorDetailer. It probably makes sense to decide whether we want such a type there before merging this and the zapr PR.

I'll prepare a logr PR for discussion.

/cc @thockin

pohly · 2026-01-23T15:13:02Z

test/zapr.go

 {"caller":"test/output.go:<LINE>","msg":"duplicates","trace":"101112131415161718191a1b1c1d1e1f","span":"0102030405060708","a":1,"v":0}
 {"caller":"test/output.go:<LINE>","msg":"duplicates","trace":"101112131415161718191a1b1c1d1e1f","span":"0102030405060708","a":1,"c":3,"trace":"101112131415161718191a1b1c1d1e1f","span":"2122232425262728","d":4,"v":0}
+`,
+		// Without support for funcr.PseudoStruct, zapr falls back to rendering a list.


With go-logr/zapr#56, zapr works as desired:

diff --git a/test/zapr.go b/test/zapr.go index be5de7e..9b5d71c 100644 --- a/test/zapr.go +++ b/test/zapr.go @@ -283,36 +283,34 @@ I output.go:<LINE>] "duplicates" trace="101112131415161718191a1b1c1d1e1f" a=1 c= {"caller":"test/output.go:<LINE>","msg":"duplicates","trace":"101112131415161718191a1b1c1d1e1f","span":"0102030405060708","a":1,"v":0} {"caller":"test/output.go:<LINE>","msg":"duplicates","trace":"101112131415161718191a1b1c1d1e1f","span":"0102030405060708","a":1,"c":3,"trace":"101112131415161718191a1b1c1d1e1f","span":"2122232425262728","d":4,"v":0} `, - // Without support for funcr.PseudoStruct, zapr falls back to rendering a list. `I output.go:<LINE>] "keys and values" parent={ boolsub=true intsub=1 recursive={ sub="level2" } multiLine=< abc def > } -`: `{"caller":"test/output.go:<LINE>","msg":"keys and values","v":0,"parent":["boolsub",true,"intsub",1,"recursive",["sub","level2"],"multiLine","abc\ndef"]} +`: `{"caller":"test/output.go:<LINE>","msg":"keys and values","v":0,"parent":{"boolsub":true,"intsub":1,"recursive":{"sub":"level2"},"multiLine":"abc\ndef"}} `, - // Errors are rendered without details by zapr. - // This is okay, they were meant to be optional. + // Errors are rendered with details by zapr, including support for PseudoStruct. `I output.go:<LINE>] "structured error" someErr="fake error" someErrDetails={ x=1 y=< multi-line string > } -`: `{"caller":"test/output.go:<LINE>","msg":"structured error","v":0,"someErr":"fake error"} +`: `{"caller":"test/output.go:<LINE>","msg":"structured error","v":0,"someErr":"fake error","someErrDetails":{"x":1,"y":"multi-line\nstring"}} `, `I output.go:<LINE>] "my structured error" someErr="fake error" someErrDetails={"SomeInt":1,"SomeString":"multi-line\nstring"} -`: `{"caller":"test/output.go:<LINE>","msg":"my structured error","v":0,"someErr":"fake error"} +`: `{"caller":"test/output.go:<LINE>","msg":"my structured error","v":0,"someErr":"fake error","someErrDetails":{"SomeInt":1,"SomeString":"multi-line\nstring"}} `, `E output.go:<LINE>] "structured error" err="fake error" errDetails={ x=1 y=< multi-line string > } -`: `{"caller":"test/output.go:<LINE>","msg":"structured error","err":"fake error"} +`: `{"caller":"test/output.go:<LINE>","msg":"structured error","err":"fake error","errDetails":{"x":1,"y":"multi-line\nstring"}} `, `E output.go:<LINE>] "my structured error" err="fake error" errDetails={"SomeInt":1,"SomeString":"multi-line\nstring"} -`: `{"caller":"test/output.go:<LINE>","msg":"my structured error","err":"fake error"} +`: `{"caller":"test/output.go:<LINE>","msg":"my structured error","err":"fake error","errDetails":{"SomeInt":1,"SomeString":"multi-line\nstring"}} `, } }

pohly · 2026-01-23T15:41:11Z

test/output.go

+	def
+ > }
+`,
+	},


TODO:

ErrorDetails implementation which crashes (should be caught by backends).

A "structured error" is an error type that implements both Error and ErrorDetails. It gets logged like a normal error with "err=<Error()>", but then another "errDetails=<ErrorDetails()>" gets added to log additional information that may be stored in the error. The result of ErrorDetails is logged like any other value. Beware that rendering of structs, in particular multi-line strings in structs, is not very readable because it all gets handled by json.Marshal. This also means that unexported fields are not logged. To get nicer output of multiple values, a PseudoStruct can be returned. Those values then are formatted one-by-one by klog, which means that multi-line strings are readable.

k8s-ci-robot added cncf-cla: yes Indicates the PR's author has signed the CNCF CLA. needs-triage Indicates an issue or PR lacks a `triage/foo` label and requires one. labels Dec 6, 2022

k8s-ci-robot requested review from dims and harshanarayana December 6, 2022 18:43

k8s-ci-robot added the size/L Denotes a PR that changes 100-499 lines, ignoring generated files. label Dec 6, 2022

k8s-ci-robot assigned harshanarayana Dec 15, 2022

k8s-ci-robot added triage/accepted Indicates an issue or PR is ready to be actively worked on. and removed needs-triage Indicates an issue or PR lacks a `triage/foo` label and requires one. labels Dec 15, 2022

k8s-ci-robot added the needs-rebase Indicates a PR cannot be merged because it has merge conflicts with HEAD. label Jan 20, 2023

pohly changed the title ~~structured error, funcr.PseudoStruct~~ WIP: structured error, funcr.PseudoStruct Feb 3, 2023

k8s-ci-robot added the do-not-merge/work-in-progress Indicates that a PR should not merge because it is a work in progress. label Feb 3, 2023

k8s-ci-robot added the lifecycle/stale Denotes an issue or PR has remained open with no activity and has become stale. label May 4, 2023

k8s-ci-robot added lifecycle/rotten Denotes an issue or PR that has aged beyond stale and will be auto-closed. and removed lifecycle/stale Denotes an issue or PR has remained open with no activity and has become stale. labels Jun 3, 2023

k8s-ci-robot removed the lifecycle/rotten Denotes an issue or PR that has aged beyond stale and will be auto-closed. label Jun 3, 2023

k8s-ci-robot added the lifecycle/stale Denotes an issue or PR has remained open with no activity and has become stale. label Apr 9, 2024

k8s-ci-robot added lifecycle/rotten Denotes an issue or PR that has aged beyond stale and will be auto-closed. and removed lifecycle/stale Denotes an issue or PR has remained open with no activity and has become stale. labels May 9, 2024

k8s-ci-robot closed this Jun 8, 2024

k8s-ci-robot reopened this Jan 8, 2026

k8s-ci-robot added the approved Indicates a PR has been approved by an approver from all required OWNERS files. label Jan 8, 2026

pohly force-pushed the structured-error-pseudo-struct branch from 2ca1701 to 57e1146 Compare January 8, 2026 13:14

k8s-ci-robot removed the needs-rebase Indicates a PR cannot be merged because it has merge conflicts with HEAD. label Jan 8, 2026

pohly force-pushed the structured-error-pseudo-struct branch from 57e1146 to 7df2671 Compare January 23, 2026 12:10

k8s-ci-robot assigned tallclair Jan 23, 2026

k8s-ci-robot added do-not-merge/hold Indicates that a PR should not merge because someone has issued a /hold command. and removed lifecycle/rotten Denotes an issue or PR that has aged beyond stale and will be auto-closed. labels Jan 23, 2026

pohly commented Jan 23, 2026

View reviewed changes

k8s-ci-robot requested a review from thockin January 23, 2026 12:15

pohly mentioned this pull request Jan 23, 2026

RFC: special types: structured error go-logr/zapr#56

Open

pohly commented Jan 23, 2026

View reviewed changes

pohly mentioned this pull request Jan 23, 2026

define types for "structured error" go-logr/logr#415

Open

pohly commented Jan 23, 2026

View reviewed changes

test/output.go

def

> }

`,

},

Copy link

Author

pohly Jan 23, 2026

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

TODO:

ErrorDetails implementation which crashes (should be caught by backends).

pohly mentioned this pull request Jan 23, 2026

[RFC] Structured Error type #357

Open

pohly force-pushed the structured-error-pseudo-struct branch from 7df2671 to f7651cc Compare January 23, 2026 16:13

Conversation

pohly commented Dec 6, 2022

Uh oh!

dashpole commented Dec 15, 2022

Uh oh!

k8s-triage-robot commented May 4, 2023

Uh oh!

k8s-triage-robot commented Jun 3, 2023

Uh oh!

pohly commented Jun 3, 2023

Uh oh!

pohly commented Jan 10, 2024

Uh oh!

k8s-triage-robot commented Apr 9, 2024

Uh oh!

k8s-triage-robot commented May 9, 2024

Uh oh!

k8s-triage-robot commented Jun 8, 2024

Uh oh!

k8s-ci-robot commented Jun 8, 2024

Uh oh!

pohly commented Jan 8, 2026

Uh oh!

k8s-ci-robot commented Jan 8, 2026

Uh oh!

k8s-ci-robot commented Jan 8, 2026

Uh oh!

pohly commented Jan 23, 2026

Uh oh!

pohly Jan 23, 2026

Choose a reason for hiding this comment

Uh oh!

pohly Jan 23, 2026

Choose a reason for hiding this comment

Uh oh!

pohly Jan 23, 2026

Choose a reason for hiding this comment

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

6 participants