slogr: add glue code for logging to slog.Handler and with slog.Logger #205

pohly · 2023-08-07T09:31:34Z

Interoperability with log/slog from Go 1.21 includes the ability to use a slog.Handler as backend with logr.Logger as frontend and vice versa.

This is only the initial step. In particular writing with slog.Logger to a logr.LogSink is not working well (time stamp and call site from record get ignored). Further work is needed to improve this.

slogr/slogr.go

pohly · 2023-08-07T09:51:05Z

Tests cover 100% of the new code lines. I also tried to consider edge cases.

slogr/sloghandler.go

thockin

I am AFK for a few days, will look more when I get back

logr.go

thockin

First commit

logr_test.go

thockin

I like having runnable examples for quick-testing. Worthing including?

diff --git a/slogr/slog_example/main.go b/slogr/slog_example/main.go
new file mode 100644
index 0000000..2e67539
--- /dev/null
+++ b/slogr/handler_example/main.go
@@ -0,0 +1,65 @@
+/*
+Copyright 2023 The logr Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+// Package main is an example of using funcr.
+package main
+
+import (
+	"context"
+	"fmt"
+	"log/slog"
+
+	"github.com/go-logr/logr/funcr"
+	"github.com/go-logr/logr/slogr"
+)
+
+type e struct {
+	str string
+}
+
+func (e e) Error() string {
+	return e.str
+}
+
+func helper(log *slog.Logger, msg string) {
+	helper2(log, msg)
+}
+
+func helper2(log *slog.Logger, msg string) {
+	log.Info(msg)
+}
+
+func main() {
+	logrLogger := funcr.New(
+		func(pfx, args string) { fmt.Println(pfx, args) },
+		funcr.Options{
+			LogCaller:    funcr.All,
+			LogTimestamp: true,
+			Verbosity:    1,
+		})
+	log := slog.New(slogr.NewSlogHandler(logrLogger))
+	example(log)
+}
+
+func example(log *slog.Logger) {
+	log = log.With("saved", "value")
+	log.Info("1) hello", "val1", 1, "val2", map[string]int{"k": 1})
+	log.Log(context.TODO(), slog.Level(-1), "2) you should see this")
+	log.Log(context.TODO(), slog.Level(-2), "you should NOT see this")
+	log.Error("3) uh oh", "trouble", true, "reasons", []float64{0.1, 0.11, 3.14})
+	log.Error("4) goodbye", "code", -1, "err", e{"an error occurred"})
+	helper(log, "5) thru a helper")
+}

In particular, this lets us verify caller information visually. I like your tests, too, and maybe we don't need both?

slogr/slogr.go

slogr/slogsink.go

slogr/sloghandler.go

slogr/slogsink.go

slogr/discardhandler.go

README.md

slogr/slogr.go

pohly · 2023-08-17T10:15:27Z

I like having runnable examples for quick-testing. Worthing including?

Yes. I merged it with the example for the other direction #205 (comment) because some parts are common (error) and this way it's easier to see both approaches without having to open two files side-by-side.

Initially, the slog.Logger calls recorded the wrong logger.go from the slog package as caller. This is inevitable, but at least for the current Go 1.21.0 and simple usage (i.e. slog.Logger directly calls the handler) it can be compensated through WithCallDepth calls - I've added that.

I like your tests, too, and maybe we don't need both?

Both = example and tests? I think we want (example) and need (tests) both.

thockin · 2023-08-17T21:52:21Z

Did you forget to add the example?

thockin

First commit only

logr.go

slogr/slogr.go

slogr/slogsink.go

slogr/sloghandler.go

pohly · 2023-08-18T06:04:36Z

Did you forget to add the example?

Yes 😢

Fixed.

The call is needed for interoperability with other logging packages when replacing the logr.Logger high-level API with some other API, like slog.Logger.

thockin · 2023-08-18T16:56:56Z

slogr/slogr.go

+
+// NewLogr returns a logr.Logger which writes to the slog.Handler.
+//
+// In the output the logr verbosity level gets negated, so V(4) becomes


Sort of a nit, but the "gets negated" is very precise. Can we write this a bit more loosely, like:

"""
NewLogr returns a logr.Logger which writes to the slog.Handler. The logr verbosity level is mapped to slog levels such that V(0) becomes slog.LevelInfo and V(4) becomes slog.LevelDebug.
"""

slogr/slogr.go

slogr/slogsink.go

thockin

closer!

thockin · 2023-08-18T18:49:58Z

slogr/sloghandler.go

+type slogHandler struct {
+	sink        logr.LogSink
+	groupPrefix string
+	level       slog.Level


rename to levelBias ?

Done, and added documentation, also for groupPrefix.

slogr/sloghandler.go

thockin · 2023-08-18T18:59:33Z

slogr/example/main.go

+	logrLogger := slogr.NewLogr(handler)
+	logrExample(logrLogger)
+
+	logrLogger = funcr.New(


NewJSON for equivalence?

thockin · 2023-08-21T22:25:04Z

slogr/slogr.go

+// error log entries with LogSink.Error, regardless of the verbosity level of
+// the logr.Logger:
+//
+//	slogLogger.Warning(...) -> logSink.Error(...)


I don't understand this line - Warning is 4, but the comment above says slog.LevelError which is 8, right?

It was simply wrong: I mis-remembered and thought that Warning >= Error.

Because Info < Warning < Error, slog.Logger.Warning can be used as example for a level that gets mapped to the same logr.Level 0 - changed.

thockin

Just that one comment I don't understand

Interoperability with log/slog from Go 1.21 includes the ability to use a slog.Handler as backend with logr.Logger as frontend and vice versa. This is only the initial step. In particular writing with slog.Logger to a logr.LogSink is not working well (time stamp and call site from record get ignored). Further work is needed to improve this.

thockin · 2023-08-22T15:44:32Z

merged!

github-actions bot assigned pohly and thockin Aug 7, 2023

pohly mentioned this pull request Aug 7, 2023

WIP: slog support #196

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4 tasks

pohly force-pushed the slog-glue branch from 0a76c45 to 01585a8 Compare August 7, 2023 09:48

pohly commented Aug 7, 2023

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pohly force-pushed the slog-glue branch 3 times, most recently from 3c7cd51 to 0b1cea0 Compare August 7, 2023 19:40

pohly mentioned this pull request Aug 8, 2023

Consider allowing PC to be passed into Handler #201

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thockin reviewed Aug 15, 2023

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pohly force-pushed the slog-glue branch 2 times, most recently from 12dd30b to 77f7a0f Compare August 17, 2023 21:28

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thockin reviewed Aug 18, 2023

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add Logger.GetV

69a3af1

The call is needed for interoperability with other logging packages when replacing the logr.Logger high-level API with some other API, like slog.Logger.

pohly force-pushed the slog-glue branch 2 times, most recently from 19c78e0 to 9b69cdd Compare August 18, 2023 07:45

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pohly force-pushed the slog-glue branch 2 times, most recently from 57acb9d to 29c6382 Compare August 21, 2023 17:46

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pohly force-pushed the slog-glue branch from 29c6382 to b50ee60 Compare August 22, 2023 06:11

thockin merged commit b785b9f into go-logr:master Aug 22, 2023

mikebrow mentioned this pull request Jan 26, 2024

Update cri-api to v0.29.1 containerd/containerd#9378

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slogr: add glue code for logging to slog.Handler and with slog.Logger #205

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slogr: add glue code for logging to slog.Handler and with slog.Logger #205

slogr: add glue code for logging to slog.Handler and with slog.Logger #205

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