From 2f30686e905cd08e2798519928c5c9749d8c8c20 Mon Sep 17 00:00:00 2001
From: Fabian Ruff <fabian.ruff@sap.com>
Date: Tue, 5 Dec 2017 14:45:27 +0100
Subject: [PATCH] Add a simple log filter that removes err=null pairs

---
 pkg/cmd/kubernikus/operator.go |  7 +++++--
 pkg/util/log/nilfilter.go      | 24 ++++++++++++++++++++++++
 2 files changed, 29 insertions(+), 2 deletions(-)
 create mode 100644 pkg/util/log/nilfilter.go

diff --git a/pkg/cmd/kubernikus/operator.go b/pkg/cmd/kubernikus/operator.go
index cd0ecf8db4..9d3b6fef14 100644
--- a/pkg/cmd/kubernikus/operator.go
+++ b/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)
diff --git a/pkg/util/log/nilfilter.go b/pkg/util/log/nilfilter.go
new file mode 100644
index 0000000000..51135f418f
--- /dev/null
+++ b/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...)
+}