observer/pkg/exporters/gelf_exporter/trace.go

package gelfexporter

import (
	"context"
	"sync"

	"git.ma-al.com/maal-libraries/observer/pkg/attr"
	"git.ma-al.com/maal-libraries/observer/pkg/level"
	"git.ma-al.com/maal-libraries/observer/pkg/syslog"
	"go.opentelemetry.io/otel/attribute"
	"go.opentelemetry.io/otel/sdk/trace"
	"go.opentelemetry.io/otel/sdk/trace/tracetest"
	"gopkg.in/Graylog2/go-gelf.v2/gelf"
)

var _ trace.SpanExporter = &Exporter{}

// New creates an Exporter with the passed options.
func New(options ...Option) (*Exporter, error) {
	cfg, err := newConfig(options...)
	if err != nil {
		return nil, err
	}

	writer, err := gelf.NewUDPWriter(cfg.GelfUrl)
	if err != nil {
		return nil, err
	}

	return &Exporter{
		gelfWriter: writer,
		appName:    cfg.AppName,
	}, nil

}

type Exporter struct {
	gelfWriter *gelf.UDPWriter
	appName    string
	stoppedMu  sync.RWMutex
	stopped    bool
}

func (e *Exporter) ExportSpans(ctx context.Context, spans []trace.ReadOnlySpan) error {
	if err := ctx.Err(); err != nil {
		return err
	}
	e.stoppedMu.RLock()
	stopped := e.stopped
	e.stoppedMu.RUnlock()
	if stopped {
		return nil
	}

	if len(spans) == 0 {
		return nil
	}

	stubs := tracetest.SpanStubsFromReadOnlySpans(spans)

	for i := range stubs {
		stub := &stubs[i]

		var attributes = make(map[string]interface{})

		for _, attr := range stub.Attributes {
			attributes[string(attr.Key)] = GetByType(attr.Value)
		}

		for _, attr := range stub.Resource.Attributes() {
			attributes[string(attr.Key)] = GetByType(attr.Value)
		}

		for i := range stub.Events {
			event := stub.Events[i]

			var gelf GELFMessage = GELFMessage{
				Host:         e.appName,
				ShortMessage: event.Name,
				Timestamp:    stub.StartTime,
				// Defaults to ALERT since we consider lack of the level a serious error that should be fixed ASAP.
				// Otherwise some dangerous unexpected behaviour could go unnoticed.
				Level: syslog.ALERT,
			}
			for _, attrKV := range event.Attributes {
				if attrKV.Key == attr.LogMessageLongKey {
					gelf.LongMessage = attrKV.Value.AsString()
					continue
				}
				if attrKV.Key == attr.LogMessageShortKey {
					gelf.ShortMessage = attrKV.Value.AsString()
					continue
				}

				if attrKV.Key == attr.SeverityLevelKey {
					gelf.Level = level.FromString(attrKV.Value.AsString()).IntoSyslogLevel()
					continue
				}

				attributes[string(attrKV.Key)] = GetByType(attrKV.Value)
			}

			gelf.ExtraFields = attributes
			Log(e.gelfWriter, gelf)
		}

	}
	return nil
}

func GetByType(val attribute.Value) interface{} {
	switch val.Type() {
	case attribute.INVALID:
		return "invalid value"
	case attribute.BOOL:
		return val.AsBool()
	case attribute.INT64:
		return val.AsInt64()
	case attribute.FLOAT64:
		return val.AsFloat64()
	case attribute.STRING:
		return val.AsString()
	case attribute.BOOLSLICE:
		return val.AsBoolSlice()
	case attribute.INT64SLICE:
		return val.AsInt64Slice()
	case attribute.FLOAT64SLICE:
		return val.AsFloat64Slice()
	case attribute.STRINGSLICE:
		return val.AsStringSlice()
	}

	return "invalid value"
}

// Shutdown is called to stop the exporter, it performs no action.
func (e *Exporter) Shutdown(ctx context.Context) error {
	e.stoppedMu.Lock()
	e.stopped = true
	e.stoppedMu.Unlock()

	return nil
}

// // MarshalLog is the marshaling function used by the logging system to represent this Exporter.
// func (e *Exporter) MarshalLog() interface{} {
// 	return struct {
// 		Type           string
// 		WithTimestamps bool
// 	}{
// 		Type:           "stdout",
// 		WithTimestamps: e.timestamps,
// 	}
// }