Severity to be emitted as metrics is configurable now

.travis.yml

@@ -0,0 +1,6 @@
+language: go
+go:
+ - 1.14.x
+
+script:
+ - go test

README.md

@@ -1,4 +1,8 @@
 # promlog
+
+[![GoDoc Widget]][GoDoc]
+
+---
 [forked klog](https://github.com/practo/klog) hook to expose the number of log messages as Prometheus metrics:
 ```
 log_messages_total{severity="ERROR"} 0
@@ -23,7 +27,7 @@ import (
 
 func main() {
 	// Create the Prometheus hook:
-	hook := promlog.MustNewPrometheusHook("")
+	hook := promlog.MustNewPrometheusHook("", klog.InfoSeverityLevel)
 
 	// Configure klog to use the Prometheus hook:
 	klog.AddHook(hook)
@@ -75,3 +79,6 @@ E0624 13:27:29.698964   51237 promlog_test.go:61] this is at error level!
 PASS
 ok  	github.com/practo/promlog	0.237s
 ```
+
+[GoDoc]: https://godoc.org/github.com/practo/promlog
+[GoDoc Widget]: https://godoc.org/github.com/practo/k8s-worker-pod-autoscaler?status.svg

example/main.go

@@ -11,7 +11,7 @@ import (
 
 func main() {
 	// Create the Prometheus hook:
-	hook := promlog.MustNewPrometheusHook("")
+	hook := promlog.MustNewPrometheusHook("", klog.InfoSeverityLevel)
 
 	// Configure klog to use the Prometheus hook:
 	klog.AddHook(hook)

promlog.go

@@ -1,10 +1,12 @@
 package promlog
 
 import (
+	"fmt"
 	"github.com/practo/klog/v2"
 	"github.com/prometheus/client_golang/prometheus"
 )
 
+// supportedSeverityLevels are the level of severities supported
 var supportedSeverityLevels = []string{
 	klog.InfoSeverityLevel,
 	klog.WarningSeverityLevel,
@@ -13,7 +15,10 @@ var supportedSeverityLevels = []string{
 
 // PrometheusHook exposes Prometheus counters for each of klog severity levels.
 type PrometheusHook struct {
-	counterVec *prometheus.CounterVec
+	// severityLevel specifies the required level for the log metrics
+	// that must be emitted as prometheus metric
+	severityLevel string
+	counterVec    *prometheus.CounterVec
 }
 
 // NewPrometheusHook creates a new instance of PrometheusHook
@@ -22,15 +27,43 @@ type PrometheusHook struct {
 // caller in case of issue.
 // Use NewPrometheusHook if you want more control.
 // Use MustNewPrometheusHook if you want a less verbose hook creation.
-func NewPrometheusHook(metricPrefix string) (*PrometheusHook, error) {
+func NewPrometheusHook(
+	metricPrefix string, severityLevel string) (*PrometheusHook, error) {
+
 	counterVec := prometheus.NewCounterVec(prometheus.CounterOpts{
-		Name:  metricPrefix + "log_messages_total",
+		Name: metricPrefix + "log_messages_total",
 		Help: "Total number of log messages.",
 	}, []string{"severity"})
+
+	var severityLevels []string
+
+	switch severityLevel {
+	case klog.InfoSeverityLevel:
+		severityLevels = []string{
+			klog.InfoSeverityLevel,
+			klog.WarningSeverityLevel,
+			klog.ErrorSeverityLevel,
+		}
+	case klog.WarningSeverityLevel:
+		severityLevels = []string{
+			klog.WarningSeverityLevel,
+			klog.ErrorSeverityLevel,
+		}
+	case klog.ErrorSeverityLevel:
+		severityLevels = []string{
+			klog.ErrorSeverityLevel,
+		}
+	default:
+		return nil, fmt.Errorf(
+			"only following severity levels are supported: %v",
+			supportedSeverityLevels)
+	}
+
 	// Initialise counters for all supported severity:
-	for _, severity := range supportedSeverityLevels {
+	for _, severity := range severityLevels {
 		counterVec.WithLabelValues(severity)
 	}
+
 	// Try to unregister the counter vector,
 	// in case already registered for some reason,
 	// e.g. double initialisation/configuration
@@ -41,8 +74,10 @@ func NewPrometheusHook(metricPrefix string) (*PrometheusHook, error) {
 	if err != nil {
 		return nil, err
 	}
+
 	return &PrometheusHook{
-		counterVec: counterVec,
+		severityLevel: severityLevel,
+		counterVec:    counterVec,
 	}, nil
 }
 
@@ -52,23 +87,27 @@ func NewPrometheusHook(metricPrefix string) (*PrometheusHook, error) {
 // any error to the caller, but panics instead.
 // Use MustNewPrometheusHook if you want a less verbose
 // hook creation. Use NewPrometheusHook if you want more control.
-func MustNewPrometheusHook(metricPrefix string) *PrometheusHook {
-	hook, err := NewPrometheusHook(metricPrefix)
+func MustNewPrometheusHook(
+	metricPrefix string, severityLevel string) *PrometheusHook {
+
+	hook, err := NewPrometheusHook(metricPrefix, severityLevel)
 	if err != nil {
 		panic(err)
 	}
+
 	return hook
 }
 
 // Fire increments the appropriate Prometheus counter
 func (hook *PrometheusHook) Fire(s string, args ...interface{}) error {
 	hook.counterVec.WithLabelValues(s).Inc()
+
 	return nil
 }
 
 // SeverityLevel can be "INFO", "WARNING", "ERROR" or "FATAL"
 // Hook will be fired in all the cases when severity is greater than
 // or equal to the severity level
 func (hook *PrometheusHook) SeverityLevel() string {
-	return klog.InfoSeverityLevel
+	return hook.severityLevel
 }

promlog_test.go

@@ -15,9 +15,10 @@ import (
 )
 
 const (
-	addr     string = ":8080"
-	endpoint string = "/metrics"
-	testPrefix string = "promlog"
+	addr              string = ":8080"
+	endpoint          string = "/metrics"
+	testSeverityLevel string = "INFO"
+	testPrefix        string = "promlog"
 )
 
 func getSeverityForLine(line string) string {
@@ -36,7 +37,7 @@ func getSeverityForLine(line string) string {
 
 func TestExposeAndQueryKlogCounters(t *testing.T) {
 	// Create Prometheus hook and configure klog to use it:
-	hook := promlog.MustNewPrometheusHook(testPrefix)
+	hook := promlog.MustNewPrometheusHook(testPrefix, testSeverityLevel)
 	klog.AddHook(hook)
 
 	server := httpServePrometheusMetrics(t)
@@ -67,6 +68,13 @@ func TestExposeAndQueryKlogCounters(t *testing.T) {
 	server.Close()
 }
 
+func TestInvalidSeverityLevel(t *testing.T) {
+	_, err := promlog.NewPrometheusHook(testPrefix, "PANIC")
+	if err == nil {
+		t.Error("expected invalid severity error")
+	}
+}
+
 // httpServePrometheusMetrics exposes the Prometheus metrics
 // over HTTP, in a different go routine.
 func httpServePrometheusMetrics(t *testing.T) *http.Server {
@@ -107,7 +115,7 @@ func countFor(t *testing.T, severity string, lines []string) int {
 	//   # TYPE test_debug counter
 	//   test_debug 0
 	metric := fmt.Sprintf(
-		testPrefix + "log_messages_total{severity=\"%v\"}", severity)
+		testPrefix+"log_messages_total{severity=\"%v\"}", severity)
 	for _, line := range lines {
 		items := strings.Split(line, " ")
 		if len(items) != 2 { // e.g. {"test_debug", "0"}