Add a otelcol.processor.transform component (#5337)

* Add a otelcol.processor.transform component

---------

Co-authored-by: Clayton Cornell <131809008+clayton-cornell@users.noreply.github.com>

CHANGELOG.md

@@ -53,6 +53,9 @@ Main (unreleased)
   - `remote.kubernetes.secret` loads a secret's data for use in other components (@captncraig)
   - `prometheus.exporter.agent` - scrape agent's metrics. (@hainenber)
   - `prometheus.exporter.vsphere` - scrape vmware vsphere metrics. (@marctc)
+  - `otelcol.processor.transform` transforms OTLP telemetry data using the 
+    OpenTelemetry Transformation Language (OTTL). It is most commonly used 
+    for transformations on attributes.
 
 - Flow: allow the HTTP server to be configured with TLS in the config file
   using the new `http` config block. (@rfratto)

component/all/all.go

@@ -81,6 +81,7 @@ import (
 	_ "github.com/grafana/agent/component/otelcol/processor/probabilistic_sampler"  // Import otelcol.processor.probabilistic_sampler
 	_ "github.com/grafana/agent/component/otelcol/processor/span"                   // Import otelcol.processor.span
 	_ "github.com/grafana/agent/component/otelcol/processor/tail_sampling"          // Import otelcol.processor.tail_sampling
+	_ "github.com/grafana/agent/component/otelcol/processor/transform"              // Import otelcol.processor.transform
 	_ "github.com/grafana/agent/component/otelcol/receiver/jaeger"                  // Import otelcol.receiver.jaeger
 	_ "github.com/grafana/agent/component/otelcol/receiver/kafka"                   // Import otelcol.receiver.kafka
 	_ "github.com/grafana/agent/component/otelcol/receiver/loki"                    // Import otelcol.receiver.loki

component/otelcol/processor/transform/transform.go

@@ -0,0 +1,173 @@
+// Package transform provides an otelcol.processor.transform component.
+package transform
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/grafana/agent/component"
+	"github.com/grafana/agent/component/otelcol"
+	"github.com/grafana/agent/component/otelcol/processor"
+	otel_service "github.com/grafana/agent/service/otel"
+	"github.com/mitchellh/mapstructure"
+	"github.com/open-telemetry/opentelemetry-collector-contrib/pkg/ottl"
+	"github.com/open-telemetry/opentelemetry-collector-contrib/processor/transformprocessor"
+	otelcomponent "go.opentelemetry.io/collector/component"
+	otelextension "go.opentelemetry.io/collector/extension"
+)
+
+func init() {
+	component.Register(component.Registration{
+		Name:          "otelcol.processor.transform",
+		Args:          Arguments{},
+		Exports:       otelcol.ConsumerExports{},
+		NeedsServices: []string{otel_service.ServiceName},
+
+		Build: func(opts component.Options, args component.Arguments) (component.Component, error) {
+			fact := transformprocessor.NewFactory()
+			return processor.New(opts, fact, args.(Arguments))
+		},
+	})
+}
+
+type ContextID string
+
+const (
+	Resource  ContextID = "resource"
+	Scope     ContextID = "scope"
+	Span      ContextID = "span"
+	SpanEvent ContextID = "spanevent"
+	Metric    ContextID = "metric"
+	DataPoint ContextID = "datapoint"
+	Log       ContextID = "log"
+)
+
+func (c *ContextID) UnmarshalText(text []byte) error {
+	str := ContextID(strings.ToLower(string(text)))
+	switch str {
+	case Resource, Scope, Span, SpanEvent, Metric, DataPoint, Log:
+		*c = str
+		return nil
+	default:
+		return fmt.Errorf("unknown context %v", str)
+	}
+}
+
+type contextStatementsSlice []contextStatements
+
+type contextStatements struct {
+	Context    ContextID `river:"context,attr"`
+	Statements []string  `river:"statements,attr"`
+}
+
+// Arguments configures the otelcol.processor.transform component.
+type Arguments struct {
+	// ErrorMode determines how the processor reacts to errors that occur while processing a statement.
+	ErrorMode        ottl.ErrorMode         `river:"error_mode,attr,optional"`
+	TraceStatements  contextStatementsSlice `river:"trace_statements,block,optional"`
+	MetricStatements contextStatementsSlice `river:"metric_statements,block,optional"`
+	LogStatements    contextStatementsSlice `river:"log_statements,block,optional"`
+
+	// Output configures where to send processed data. Required.
+	Output *otelcol.ConsumerArguments `river:"output,block"`
+}
+
+var (
+	_ processor.Arguments = Arguments{}
+)
+
+// DefaultArguments holds default settings for Arguments.
+var DefaultArguments = Arguments{
+	ErrorMode: ottl.PropagateError,
+}
+
+// SetToDefault implements river.Defaulter.
+func (args *Arguments) SetToDefault() {
+	*args = DefaultArguments
+}
+
+// Validate implements river.Validator.
+func (args *Arguments) Validate() error {
+	otelArgs, err := args.convertImpl()
+	if err != nil {
+		return err
+	}
+	return otelArgs.Validate()
+}
+
+func (stmts *contextStatementsSlice) convert() []interface{} {
+	if stmts == nil {
+		return nil
+	}
+
+	res := make([]interface{}, 0, len(*stmts))
+
+	if len(*stmts) == 0 {
+		return res
+	}
+
+	for _, stmt := range *stmts {
+		res = append(res, stmt.convert())
+	}
+	return res
+}
+
+func (args *contextStatements) convert() map[string]interface{} {
+	if args == nil {
+		return nil
+	}
+
+	return map[string]interface{}{
+		"context":    args.Context,
+		"statements": args.Statements,
+	}
+}
+
+// Convert implements processor.Arguments.
+func (args Arguments) Convert() (otelcomponent.Config, error) {
+	return args.convertImpl()
+}
+
+// convertImpl is a helper function which returns the real type of the config,
+// instead of the otelcomponent.Config interface.
+func (args Arguments) convertImpl() (*transformprocessor.Config, error) {
+	input := make(map[string]interface{})
+
+	input["error_mode"] = args.ErrorMode
+
+	if len(args.TraceStatements) > 0 {
+		input["trace_statements"] = args.TraceStatements.convert()
+	}
+
+	if len(args.MetricStatements) > 0 {
+		input["metric_statements"] = args.MetricStatements.convert()
+	}
+
+	if len(args.LogStatements) > 0 {
+		input["log_statements"] = args.LogStatements.convert()
+	}
+
+	var result transformprocessor.Config
+	err := mapstructure.Decode(input, &result)
+
+	if err != nil {
+		return nil, err
+	}
+
+	return &result, nil
+}
+
+// Extensions implements processor.Arguments.
+func (args Arguments) Extensions() map[otelcomponent.ID]otelextension.Extension {
+	return nil
+}
+
+// Exporters implements processor.Arguments.
+func (args Arguments) Exporters() map[otelcomponent.DataType]map[otelcomponent.ID]otelcomponent.Component {
+	return nil
+}
+
+// NextConsumers implements processor.Arguments.
+func (args Arguments) NextConsumers() *otelcol.ConsumerArguments {
+	return args.Output
+}