MF-139 - Expose metrics from all services (#213)

* Expose metrics from normalizer service

Add service interface in order to expose method to be monitored.

Signed-off-by: Dušan Borovčanin <borovcanindusan1@gmail.com>

* Refactor normalizer

Add metrics to normalizer service without exporting its internals.

Signed-off-by: Dušan Borovčanin <borovcanindusan1@gmail.com>

cmd/normalizer/main.go

@@ -11,6 +11,9 @@ import (
 	"github.com/mainflux/mainflux"
 	"github.com/mainflux/mainflux/normalizer"
 	nats "github.com/nats-io/go-nats"
+
+	kitprometheus "github.com/go-kit/kit/metrics/prometheus"
+	stdprometheus "github.com/prometheus/client_golang/prometheus"
 )
 
 const (
@@ -55,6 +58,20 @@ func main() {
 		errs <- fmt.Errorf("%s", <-c)
 	}()
 
-	normalizer.Subscribe(nc, logger)
+	counter := kitprometheus.NewCounterFrom(stdprometheus.CounterOpts{
+		Namespace: "normalizer",
+		Subsystem: "api",
+		Name:      "request_count",
+		Help:      "Number of requests received.",
+	}, []string{"method"})
+
+	latency := kitprometheus.NewSummaryFrom(stdprometheus.SummaryOpts{
+		Namespace: "normalizer",
+		Subsystem: "api",
+		Name:      "request_latency_microseconds",
+		Help:      "Total duration of requests in microseconds.",
+	}, []string{"method"})
+
+	normalizer.Subscribe(nc, logger, counter, latency)
 	logger.Log("terminated", <-errs)
 }

normalizer/metrics.go

@@ -0,0 +1,30 @@
+package normalizer
+
+import (
+	"time"
+
+	"github.com/go-kit/kit/metrics"
+	nats "github.com/nats-io/go-nats"
+)
+
+type metricsMiddleware struct {
+	counter metrics.Counter
+	latency metrics.Histogram
+	ef      eventFlow
+}
+
+func newMetricsMiddleware(ef eventFlow, counter metrics.Counter, latency metrics.Histogram) *metricsMiddleware {
+	return &metricsMiddleware{
+		counter: counter,
+		latency: latency,
+		ef:      ef,
+	}
+}
+
+func (mm *metricsMiddleware) handleMessage(msg *nats.Msg) {
+	defer func(begin time.Time) {
+		mm.counter.With("method", "handleMessage").Add(1)
+		mm.latency.With("method", "handleMessage").Observe(time.Since(begin).Seconds())
+	}(time.Now())
+	mm.ef.handleMsg(msg)
+}

normalizer/normalizer.go

@@ -5,6 +5,7 @@ import (
 
 	"github.com/cisco/senml"
 	"github.com/go-kit/kit/log"
+	"github.com/go-kit/kit/metrics"
 	"github.com/golang/protobuf/proto"
 	"github.com/mainflux/mainflux"
 	nats "github.com/nats-io/go-nats"
@@ -22,25 +23,24 @@ type eventFlow struct {
 }
 
 // Subscribe instantiates and starts a new NATS message flow.
-func Subscribe(nc *nats.Conn, logger log.Logger) {
+func Subscribe(nc *nats.Conn, logger log.Logger, counter metrics.Counter, latency metrics.Histogram) {
 	flow := eventFlow{nc, logger}
-	flow.start()
+	mm := newMetricsMiddleware(flow, counter, latency)
+	flow.nc.QueueSubscribe(subject, queue, mm.handleMessage)
 }
 
-func (ef eventFlow) start() {
-	ef.nc.QueueSubscribe(subject, queue, func(m *nats.Msg) {
-		msg := mainflux.RawMessage{}
+func (ef eventFlow) handleMsg(m *nats.Msg) {
+	msg := mainflux.RawMessage{}
 
-		if err := proto.Unmarshal(m.Data, &msg); err != nil {
-			ef.logger.Log("error", fmt.Sprintf("Unmarshalling failed: %s", err))
-			return
-		}
+	if err := proto.Unmarshal(m.Data, &msg); err != nil {
+		ef.logger.Log("error", fmt.Sprintf("Unmarshalling failed: %s", err))
+		return
+	}
 
-		if err := ef.publish(msg); err != nil {
-			ef.logger.Log("error", fmt.Sprintf("Publishing failed: %s", err))
-			return
-		}
-	})
+	if err := ef.publish(msg); err != nil {
+		ef.logger.Log("error", fmt.Sprintf("Publishing failed: %s", err))
+		return
+	}
 }
 
 func (ef eventFlow) publish(msg mainflux.RawMessage) error {