fix(#2076): make db.response.error attribute selection consistent with other optional attributes

devdocs/config/CONFIG.md

@@ -62,7 +62,7 @@ Attributes configures the decoration of some extra attributes that will be added
 | `attributes.rename_unresolved_hosts` | `string` | `OTEL_EBPF_RENAME_UNRESOLVED_HOSTS` | `unresolved` |  |  | Will replace HostName and PeerName attributes when they are empty or contain unresolved IP addresses to reduce cardinality. Set this value to the empty string to disable this feature. |
 | `attributes.rename_unresolved_hosts_incoming` | `string` | `OTEL_EBPF_RENAME_UNRESOLVED_HOSTS_INCOMING` | `incoming` |  |  |  |
 | `attributes.rename_unresolved_hosts_outgoing` | `string` | `OTEL_EBPF_RENAME_UNRESOLVED_HOSTS_OUTGOING` | `outgoing` |  |  |  |
-| `attributes.select` | `map[string]object` |  |  |  |  | Selection specifies which attributes are allowed for each metric. The key is the metric name (either in Prometheus or OpenTelemetry format) The value is the enumeration of included/excluded attribute globs |
+| `attributes.select` | `map[string]object` |  |  |  |  | Selection specifies which attributes are allowed for each signal. The key is usually the metric name (either in Prometheus or OpenTelemetry format); the key "traces" selects optional attributes for exported OTLP traces. The value is the enumeration of included/excluded attribute globs |
 
 ### `attributes.host_id`
 

devdocs/config/config-schema.json

@@ -2516,7 +2516,7 @@
         "$ref": "#/$defs/InclusionLists"
       },
       "type": "object",
-      "description": "Selection specifies which attributes are allowed for each metric. The key is the metric name (either in Prometheus or OpenTelemetry format) The value is the enumeration of included/excluded attribute globs"
+      "description": "Selection specifies which attributes are allowed for each signal. The key is usually the metric name (either in Prometheus or OpenTelemetry format); the key \"traces\" selects optional attributes for exported OTLP traces. The value is the enumeration of included/excluded attribute globs"
     },
     "StatsConfig": {
       "properties": {

pkg/appolly/app/request/span_test.go

@@ -334,7 +334,7 @@ func TestSpanStatusMessage_DBResponseErrorOptional(t *testing.T) {
 				Status:  1,
 				DBError: DBError{ErrorCode: "WRONGTYPE", Description: "WRONGTYPE Operation against a key holding the wrong kind of value"},
 			},
-			expectedDefault: attributes.DBErrorMessagePlaceholder,
+			expectedDefault: "",
 			expectedAllowed: "WRONGTYPE Operation against a key holding the wrong kind of value",
 		},
 		{
@@ -344,7 +344,7 @@ func TestSpanStatusMessage_DBResponseErrorOptional(t *testing.T) {
 				Status:   1,
 				SQLError: &SQLError{Code: 8, SQLState: "ABC", Message: "SQL error message"},
 			},
-			expectedDefault: attributes.DBErrorMessagePlaceholder,
+			expectedDefault: "",
 			expectedAllowed: "SQL Server errored: error_code=8 sql_state=ABC message=SQL error message",
 		},
 		{
@@ -355,7 +355,7 @@ func TestSpanStatusMessage_DBResponseErrorOptional(t *testing.T) {
 				Status:  1,
 				DBError: DBError{ErrorCode: "12003", Description: "Keyspace not found in CB datastore"},
 			},
-			expectedDefault: attributes.DBErrorMessagePlaceholder,
+			expectedDefault: "",
 			expectedAllowed: "Keyspace not found in CB datastore",
 		},
 		{

pkg/export/attributes/attr_defs.go

@@ -525,17 +525,15 @@ func AllAttributeNames(
 	return names
 }
 
-const (
-	DBErrorMessagePlaceholder = "enable the db.response.error attribute for details"
-)
-
-// DBResponseErrorAttr returns a database response error attribute or a placeholder if the attribute is not selected
+// DBResponseErrorAttr returns a database response error attribute if the attribute is selected, nil otherwise.
+// When the attribute is not selected, it is simply omitted — consistent with how other optional
+// attributes (e.g. db.query.text) behave.
 func DBResponseErrorAttr(optionalAttrs map[attr.Name]struct{}, description string) []attribute.KeyValue {
 	if description == "" {
 		return nil
 	}
 	if _, ok := optionalAttrs[attr.DBResponseError]; !ok {
-		return []attribute.KeyValue{attribute.Key(attr.DBResponseError).String(DBErrorMessagePlaceholder)}
+		return nil
 	}
 	return []attribute.KeyValue{attribute.Key(attr.DBResponseError).String(description)}
 }

pkg/export/attributes/attr_select.go

@@ -12,8 +12,9 @@ import (
 	attr "go.opentelemetry.io/obi/pkg/export/attributes/names"
 )
 
-// Selection specifies which attributes are allowed for each metric.
-// The key is the metric name (either in Prometheus or OpenTelemetry format)
+// Selection specifies which attributes are allowed for each signal.
+// The key is usually the metric name (either in Prometheus or OpenTelemetry format);
+// the key "traces" selects optional attributes for exported OTLP traces.
 // The value is the enumeration of included/excluded attribute globs
 type Selection map[Section]InclusionLists
 

pkg/export/otel/traces_test.go

@@ -387,7 +387,7 @@ func TestGenerateTracesAttributes(t *testing.T) {
 		attrs := spans.At(0).Attributes()
 		status := spans.At(0).Status()
 		assert.Equal(t, ptrace.StatusCodeError, status.Code())
-		assert.Equal(t, attributes.DBErrorMessagePlaceholder, status.Message())
+		assert.Empty(t, status.Message())
 
 		assert.Equal(t, 9, attrs.Len())
 
@@ -533,7 +533,7 @@ func TestGenerateTracesAttributes(t *testing.T) {
 		ensureTraceAttrNotExists(t, attrs, attribute.Key(attr.DBQueryText))
 		ensureTraceAttrNotExists(t, attrs, attribute.Key(attr.DBResponseError))
 		assert.Equal(t, ptrace.StatusCodeError, spans.At(0).Status().Code())
-		assert.Equal(t, attributes.DBErrorMessagePlaceholder, spans.At(0).Status().Message())
+		assert.Empty(t, spans.At(0).Status().Message())
 	})
 	t.Run("test Couchbase trace generation", func(t *testing.T) {
 		span := request.Span{Type: request.EventTypeCouchbaseClient, Method: "GET", Path: "mycollection", DBNamespace: "mybucket.myscope", Status: 0}
@@ -582,7 +582,7 @@ func TestGenerateTracesAttributes(t *testing.T) {
 		ensureTraceAttrNotExists(t, attrs, attribute.Key(attr.DBQueryText))
 		ensureTraceAttrNotExists(t, attrs, attribute.Key(attr.DBResponseError))
 		assert.Equal(t, ptrace.StatusCodeError, spans.At(0).Status().Code())
-		assert.Equal(t, attributes.DBErrorMessagePlaceholder, spans.At(0).Status().Message())
+		assert.Empty(t, spans.At(0).Status().Message())
 	})
 	t.Run("test Couchbase trace generation with db.query.text", func(t *testing.T) {
 		span := request.Span{
@@ -679,7 +679,7 @@ func TestGenerateTracesAttributes(t *testing.T) {
 		ensureTraceAttrNotExists(t, attrs, semconv.PeerServiceKey)
 		ensureTraceAttrNotExists(t, attrs, attribute.Key(attr.DBResponseError))
 		assert.Equal(t, ptrace.StatusCodeError, spans.At(0).Status().Code())
-		assert.Equal(t, attributes.DBErrorMessagePlaceholder, spans.At(0).Status().Message())
+		assert.Empty(t, spans.At(0).Status().Message())
 	})
 	t.Run("test SQL++ trace generation", func(t *testing.T) {
 		span := request.Span{
@@ -789,7 +789,7 @@ func TestGenerateTracesAttributes(t *testing.T) {
 		ensureTraceStrAttr(t, attrs, attribute.Key(attr.DBResponseStatusCode), "12003")
 		ensureTraceAttrNotExists(t, attrs, attribute.Key(attr.DBResponseError))
 		assert.Equal(t, ptrace.StatusCodeError, spans.At(0).Status().Code())
-		assert.Equal(t, attributes.DBErrorMessagePlaceholder, spans.At(0).Status().Message())
+		assert.Empty(t, spans.At(0).Status().Message())
 	})
 	t.Run("test SQL++ trace generation with minimal attributes", func(t *testing.T) {
 		span := request.Span{