Increase instrument name maximum length from 63 to 255 characters

CHANGELOG.md

@@ -44,6 +44,7 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 - Restrict `Meter`s in `go.opentelemetry.io/otel/sdk/metric` to only register and collect instruments it created. (#4333)
 - `PeriodicReader.Shutdown` and `PeriodicReader.ForceFlush` in `go.opentelemetry.io/otel/sdk/metric` now apply the periodic reader's timeout to the operation if the user provided context does not contain a deadline. (#4356, #4377)
 - Upgrade all use of `go.opentelemetry.io/otel/semconv` to use `v1.21.0`. (#4408)
+- Increase instrument name maximum length from 63 to 255 characters. (#4434)
 
 ### Fixed
 

sdk/metric/meter.go

@@ -28,7 +28,7 @@ import (
 
 var (
 	// ErrInstrumentName indicates the created instrument has an invalid name.
-	// Valid names must consist of 63 or fewer characters including alphanumeric, _, ., -, and start with a letter.
+	// Valid names must consist of 255 or fewer characters including alphanumeric, _, ., -, and start with a letter.
 	ErrInstrumentName = errors.New("invalid instrument name")
 )
 
@@ -252,8 +252,8 @@ func validateInstrumentName(name string) error {
 	if len(name) == 0 {
 		return fmt.Errorf("%w: %s: is empty", ErrInstrumentName, name)
 	}
-	if len(name) > 63 {
-		return fmt.Errorf("%w: %s: longer than 63 characters", ErrInstrumentName, name)
+	if len(name) > 255 {
+		return fmt.Errorf("%w: %s: longer than 255 characters", ErrInstrumentName, name)
 	}
 	if !isAlpha([]rune(name)[0]) {
 		return fmt.Errorf("%w: %s: must start with a letter", ErrInstrumentName, name)

sdk/metric/meter_test.go

@@ -743,6 +743,11 @@ func TestMeterCreatesInstrumentsValidations(t *testing.T) {
 }
 
 func TestValidateInstrumentName(t *testing.T) {
+	const longName = "longValidNameOver255characters" +
+		"xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx" +
+		"xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx" +
+		"xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx" +
+		"xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"
 	testCases := []struct {
 		name string
 
@@ -776,8 +781,8 @@ func TestValidateInstrumentName(t *testing.T) {
 			wantErr: fmt.Errorf("%w: name!: must only contain [A-Za-z0-9_.-]", ErrInstrumentName),
 		},
 		{
-			name:    "someverylongnamewhichisover63charactersbutallofwhichmatchtheregexp",
-			wantErr: fmt.Errorf("%w: someverylongnamewhichisover63charactersbutallofwhichmatchtheregexp: longer than 63 characters", ErrInstrumentName),
+			name:    longName,
+			wantErr: fmt.Errorf("%w: %s: longer than 255 characters", ErrInstrumentName, longName),
 		},
 	}