ErrorHandlerFunc: add error log fields based on function reflection

handlers.go

@@ -21,6 +21,8 @@
 package tchannel
 
 import (
+	"reflect"
+	"runtime"
 	"sync"
 
 	"golang.org/x/net/context"
@@ -50,14 +52,25 @@ type ErrorHandlerFunc func(ctx context.Context, call *InboundCall) error
 // Handle calls f(ctx, call)
 func (f ErrorHandlerFunc) Handle(ctx context.Context, call *InboundCall) {
 	if err := f(ctx, call); err != nil {
-		call.log.WithFields(ErrField(err)).Error("Handler error.")
-		resp := call.Response()
-		if err := resp.SendSystemError(err); err != nil {
-			call.log.WithFields(ErrField(err)).Error("Failed to send system error.")
+		log := call.log.WithFields(f.getLogFields()...)
+		log.WithFields(ErrField(err)).Error("Handler error.")
+		if err := call.Response().SendSystemError(err); err != nil {
+			log.WithFields(ErrField(err)).Error("Failed to send system error.")
 		}
 	}
 }
 
+func (f ErrorHandlerFunc) getLogFields() LogFields {
+	ptr := reflect.ValueOf(f).Pointer()
+	handlerFunc := runtime.FuncForPC(ptr) // can't be nil
+	fileName, fileLine := handlerFunc.FileLine(ptr)
+	return LogFields{
+		{"handlerFuncName", handlerFunc.Name()},
+		{"handlerFuncFileName", fileName},
+		{"handlerFuncFileLine", fileLine},
+	}
+}
+
 // Manages handlers
 type handlerMap struct {
 	sync.RWMutex