Add a simple log filter that removes err=null pairs

pkg/cmd/kubernikus/operator.go

@@ -10,11 +10,13 @@ import (
 
 	"github.com/go-kit/kit/log"
 	"github.com/golang/glog"
+	"github.com/spf13/cobra"
+	"github.com/spf13/pflag"
+
 	"github.com/sapcc/kubernikus/pkg/cmd"
 	"github.com/sapcc/kubernikus/pkg/controller"
 	"github.com/sapcc/kubernikus/pkg/controller/metrics"
-	"github.com/spf13/cobra"
-	"github.com/spf13/pflag"
+	logutil "github.com/sapcc/kubernikus/pkg/util/log"
 )
 
 func NewOperatorCommand() *cobra.Command {
@@ -90,6 +92,7 @@ func (o *Options) Complete(args []string) error {
 func (o *Options) Run(c *cobra.Command) error {
 	var logger log.Logger
 	logger = log.NewLogfmtLogger(log.NewSyncWriter(os.Stderr))
+	logger = logutil.NewTrailingNilFilter(logger)
 	logger = log.With(logger, "ts", log.DefaultTimestampUTC, "caller", log.DefaultCaller)
 
 	sigs := make(chan os.Signal, 1)

pkg/util/log/nilfilter.go

@@ -0,0 +1,24 @@
+package log
+
+import (
+	kitlog "github.com/go-kit/kit/log"
+)
+
+type nilFilter struct {
+	next kitlog.Logger
+}
+
+// NewTrailingNilFilter removes key values pairs at the end with a nil value
+// This mainly for getting rid of  err=null trailers
+func NewTrailingNilFilter(logger kitlog.Logger) kitlog.Logger {
+	return &nilFilter{next: logger}
+}
+
+func (l nilFilter) Log(keyvals ...interface{}) error {
+	for i := len(keyvals) - 1; i > 0; i -= 2 {
+		if keyvals[i] != nil {
+			return l.next.Log(keyvals[:i+1]...)
+		}
+	}
+	return l.next.Log(keyvals...)
+}