Added integration support for DataDog APM Tracing

vendor/gopkg.in/DataDog/dd-trace-go.v1/ddtrace/tracer/errors.go

@@ -0,0 +1,69 @@
+package tracer
+
+import (
+	"fmt"
+	"log"
+	"strconv"
+)
+
+var errorPrefix = fmt.Sprintf("Datadog Tracer Error (%s): ", tracerVersion)
+
+type traceEncodingError struct{ context error }
+
+func (e *traceEncodingError) Error() string {
+	return fmt.Sprintf("error encoding trace: %s", e.context)
+}
+
+type spanBufferFullError struct{}
+
+func (e *spanBufferFullError) Error() string {
+	return fmt.Sprintf("trace span cap (%d) reached, dropping trace", traceMaxSize)
+}
+
+type dataLossError struct {
+	count   int   // number of items lost
+	context error // any context error, if available
+}
+
+func (e *dataLossError) Error() string {
+	return fmt.Sprintf("lost traces (count: %d), error: %v", e.count, e.context)
+}
+
+type errorSummary struct {
+	Count   int
+	Example string
+}
+
+func aggregateErrors(errChan <-chan error) map[string]errorSummary {
+	errs := make(map[string]errorSummary, len(errChan))
+	for {
+		select {
+		case err := <-errChan:
+			if err == nil {
+				break
+			}
+			key := fmt.Sprintf("%T", err)
+			summary := errs[key]
+			summary.Count++
+			summary.Example = err.Error()
+			errs[key] = summary
+		default: // stop when there's no more data
+			return errs
+		}
+	}
+}
+
+// logErrors logs the errors, preventing log file flooding, when there
+// are many messages, it caps them and shows a quick summary.
+// As of today it only logs using standard golang log package, but
+// later we could send those stats to agent // TODO(ufoot).
+func logErrors(errChan <-chan error) {
+	errs := aggregateErrors(errChan)
+	for _, v := range errs {
+		var repeat string
+		if v.Count > 1 {
+			repeat = " (repeated " + strconv.Itoa(v.Count) + " times)"
+		}
+		log.Println(errorPrefix + v.Example + repeat)
+	}
+}