fix key/pattern logic for the attribute processor (#2124)

CHANGELOG.md

@@ -30,6 +30,8 @@ Main (unreleased)
 
 - Fixed issue with reloading configuration and prometheus metrics duplication in `prometheus.write.queue`. (@mattdurham)
 
+- Fixed an issue in the `otelcol.processor.attribute` component where the actions `delete` and `hash` could not be used with the `pattern` argument. (@wildum) 
+
 ### Other changes
 
 - Change the stability of the `livedebugging` feature from "experimental" to "generally available". (@wildum)

internal/component/otelcol/config_attraction.go

@@ -1,5 +1,16 @@
 package otelcol
 
+import (
+	"errors"
+	"fmt"
+	"strings"
+)
+
+const (
+	delete = "delete"
+	hash   = "hash"
+)
+
 type AttrActionKeyValueSlice []AttrActionKeyValue
 
 func (actions AttrActionKeyValueSlice) Convert() []interface{} {
@@ -15,10 +26,27 @@ func (actions AttrActionKeyValueSlice) Convert() []interface{} {
 	return res
 }
 
+func (actions AttrActionKeyValueSlice) Validate() error {
+	var validationErrors []error
+
+	for i, action := range actions {
+		if err := action.validate(); err != nil {
+			wrappedErr := fmt.Errorf("validation failed for action block number %d: %w", i+1, err)
+			validationErrors = append(validationErrors, wrappedErr)
+		}
+	}
+
+	if len(validationErrors) > 0 {
+		return errors.Join(validationErrors...)
+	}
+	return nil
+}
+
 type AttrActionKeyValue struct {
 	// Key specifies the attribute to act upon.
-	// This is a required field.
-	Key string `alloy:"key,attr"`
+	// The actions `delete` and `hash` can use the `pattern`` argument instead of/with the `key` argument.
+	// The field is required for all other actions.
+	Key string `alloy:"key,attr,optional"`
 
 	// Value specifies the value to populate for the key.
 	// The type of the value is inferred from the configuration.
@@ -91,3 +119,17 @@ func (args *AttrActionKeyValue) convert() map[string]interface{} {
 		"converted_type": args.ConvertedType,
 	}
 }
+
+func (args *AttrActionKeyValue) validate() error {
+	switch strings.ToLower(args.Action) {
+	case delete, hash:
+		if args.Key == "" && args.RegexPattern == "" {
+			return fmt.Errorf("the action %s requires at least the key argument or the pattern argument to be set", args.Action)
+		}
+	default:
+		if args.Key == "" {
+			return fmt.Errorf("the action %s requires the key argument to be set", args.Action)
+		}
+	}
+	return nil
+}

internal/component/otelcol/config_attraction_test.go

@@ -1,6 +1,7 @@
 package otelcol_test
 
 import (
+	"strings"
 	"testing"
 
 	"github.com/grafana/alloy/internal/component/otelcol"
@@ -58,3 +59,56 @@ func TestConvertAttrAction(t *testing.T) {
 	result := inputActions.Convert()
 	require.Equal(t, expectedActions, result)
 }
+
+func TestValidateAttrAction(t *testing.T) {
+	inputActions := otelcol.AttrActionKeyValueSlice{
+		{
+			// ok - only key
+			Action: "insert",
+			Value:  123,
+			Key:    "attribute1",
+		},
+		{
+			// not ok - missing key
+			Action:       "insert",
+			Value:        123,
+			RegexPattern: "pattern", // pattern is useless here
+		},
+		{
+			// ok - only key
+			Action: "delete",
+			Key:    "key",
+		},
+		{
+			// ok - only pattern
+			Action:       "delete",
+			RegexPattern: "pattern",
+		},
+		{
+			// ok - both
+			Action:       "delete",
+			Key:          "key",
+			RegexPattern: "pattern",
+		},
+		{
+			// not ok - missing key and pattern
+			Action: "delete",
+		},
+		{
+			// ok - only pattern
+			Action:       "hash",
+			RegexPattern: "pattern",
+		},
+		{
+			// ok - with uppercase
+			Action:       "HaSH",
+			RegexPattern: "pattern",
+		},
+	}
+
+	expectedErrors := []string{
+		"validation failed for action block number 2: the action insert requires the key argument to be set",
+		"validation failed for action block number 6: the action delete requires at least the key argument or the pattern argument to be set",
+	}
+	require.EqualError(t, inputActions.Validate(), strings.Join(expectedErrors, "\n"))
+}

internal/component/otelcol/processor/attributes/attributes.go

@@ -55,6 +55,10 @@ func (args *Arguments) SetToDefault() {
 	args.DebugMetrics.SetToDefault()
 }
 
+func (args *Arguments) Validate() error {
+	return args.Actions.Validate()
+}
+
 // Convert implements processor.Arguments.
 func (args Arguments) Convert() (otelcomponent.Config, error) {
 	input := make(map[string]interface{})

internal/component/otelcol/processor/attributes/attributes_test.go

@@ -134,6 +134,23 @@ func testRunProcessorWithContext(ctx context.Context, t *testing.T, processorCon
 	processortest.TestRunProcessor(prc)
 }
 
+// Test that the validate function is called. The validation logic for the actions is tested in the otelcol pkg.
+func Test_Validate(t *testing.T) {
+	cfg := `
+		action {
+			value = 111111
+			action = "insert"
+		}
+
+		output {
+			// no-op: will be overridden by test code.
+		}
+	`
+	expectedErr := "validation failed for action block number 1: the action insert requires the key argument to be set"
+	var args attributes.Arguments
+	require.ErrorContains(t, syntax.Unmarshal([]byte(cfg), &args), expectedErr)
+}
+
 func Test_Insert(t *testing.T) {
 	cfg := `
 		action {