Enhance internal logging (#3900)

* Introduce `Warn` function in global package

* Cover log levels with tests

---------

Co-authored-by: Robert Pająk <pellared@hotmail.com>
Co-authored-by: Aaron Clawson <3766680+MadVikingGod@users.noreply.github.com>

CHANGELOG.md

@@ -14,6 +14,7 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 - The new `Exemplar` type is added to `go.opentelemetry.io/otel/sdk/metric/metricdata`.
   Both the `DataPoint` and `HistogramDataPoint` types from that package have a new field of `Exemplars` containing the sampled exemplars for their timeseries. (#3849)
 - Configuration for each metric instrument in `go.opentelemetry.io/otel/sdk/metric/instrument`. (#3895)
+- The internal logging introduces a warning level verbosity equal to `V(1)`. (#3900)
 
 ### Changed
 
@@ -29,6 +30,7 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
   - `NewNoopMeter` is replaced with `noop.NewMeterProvider().Meter("")`
 - Rename `Int64ObserverOption` to `Int64ObservableOption` in `go.opentelemetry.io/otel/metric/instrument`. (#3895)
 - Rename `Float64ObserverOption` to `Float64ObservableOption` in `go.opentelemetry.io/otel/metric/instrument`. (#3895)
+- The internal logging changes the verbosity level of info to `V(4)`, the verbosity level of debug to `V(8)`. (#3900)
 
 ### Removed
 

internal/global/internal_logging.go

@@ -24,7 +24,7 @@ import (
 	"github.com/go-logr/stdr"
 )
 
-// globalLogger is the logging interface used within the otel api and sdk provide deatails of the internals.
+// globalLogger is the logging interface used within the otel api and sdk provide details of the internals.
 //
 // The default logger uses stdr which is backed by the standard `log.Logger`
 // interface. This logger will only show messages at the Error Level.
@@ -36,8 +36,9 @@ func init() {
 
 // SetLogger overrides the globalLogger with l.
 //
-// To see Info messages use a logger with `l.V(1).Enabled() == true`
-// To see Debug messages use a logger with `l.V(5).Enabled() == true`.
+// To see Warn messages use a logger with `l.V(1).Enabled() == true`
+// To see Info messages use a logger with `l.V(4).Enabled() == true`
+// To see Debug messages use a logger with `l.V(8).Enabled() == true`.
 func SetLogger(l logr.Logger) {
 	atomic.StorePointer(&globalLogger, unsafe.Pointer(&l))
 }
@@ -47,9 +48,9 @@ func getLogger() logr.Logger {
 }
 
 // Info prints messages about the general state of the API or SDK.
-// This should usually be less then 5 messages a minute.
+// This should usually be less than 5 messages a minute.
 func Info(msg string, keysAndValues ...interface{}) {
-	getLogger().V(1).Info(msg, keysAndValues...)
+	getLogger().V(4).Info(msg, keysAndValues...)
 }
 
 // Error prints messages about exceptional states of the API or SDK.
@@ -59,5 +60,11 @@ func Error(err error, msg string, keysAndValues ...interface{}) {
 
 // Debug prints messages about all internal changes in the API or SDK.
 func Debug(msg string, keysAndValues ...interface{}) {
-	getLogger().V(5).Info(msg, keysAndValues...)
+	getLogger().V(8).Info(msg, keysAndValues...)
+}
+
+// Warn prints messages about warnings in the API or SDK.
+// Not an error but is likely more important than an informational event.
+func Warn(msg string, keysAndValues ...interface{}) {
+	getLogger().V(1).Info(msg, keysAndValues...)
 }

internal/global/internal_logging_test.go

@@ -15,10 +15,17 @@
 package global
 
 import (
+	"bytes"
+	"errors"
 	"log"
 	"os"
 	"testing"
 
+	"github.com/go-logr/logr"
+
+	"github.com/stretchr/testify/assert"
+
+	"github.com/go-logr/logr/funcr"
 	"github.com/go-logr/stdr"
 )
 
@@ -26,3 +33,64 @@ func TestRace(t *testing.T) {
 	go SetLogger(stdr.New(log.New(os.Stderr, "", 0)))
 	go Info("")
 }
+
+func TestLogLevel(t *testing.T) {
+	tests := []struct {
+		name      string
+		verbosity int
+		logF      func()
+		want      string
+	}{
+		{
+			name:      "Verbosity 0 should log errors.",
+			verbosity: 0,
+			want:      `"msg"="foobar" "error"="foobar"`,
+			logF: func() {
+				Error(errors.New("foobar"), "foobar")
+			},
+		},
+		{
+			name:      "Verbosity 1 should log warnings",
+			verbosity: 1,
+			want:      `"level"=1 "msg"="foo"`,
+			logF: func() {
+				Warn("foo")
+			},
+		},
+		{
+			name:      "Verbosity 4 should log info",
+			verbosity: 4,
+			want:      `"level"=4 "msg"="bar"`,
+			logF: func() {
+				Info("bar")
+			},
+		},
+		{
+			name:      "Verbosity 8 should log debug",
+			verbosity: 8,
+			want:      `"level"=8 "msg"="baz"`,
+			logF: func() {
+				Debug("baz")
+			},
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			var buf bytes.Buffer
+			SetLogger(newBuffLogger(&buf, test.verbosity))
+
+			test.logF()
+
+			assert.Equal(t, test.want, buf.String())
+		})
+	}
+}
+
+func newBuffLogger(buf *bytes.Buffer, verbosity int) logr.Logger {
+	return funcr.New(func(prefix, args string) {
+		_, _ = buf.Write([]byte(args))
+	}, funcr.Options{
+		Verbosity: verbosity,
+	})
+}