HTTP client Prometheus metrics (#354)

Signed-off-by: George Christou <[email protected]>

client/http/http.go

@@ -7,22 +7,42 @@ import (
 	"context"
 	"io"
 	"net/http"
+	"strconv"
 	"time"
 
+	"github.com/opentracing-contrib/go-stdlib/nethttp"
+	"github.com/opentracing/opentracing-go"
+	"github.com/opentracing/opentracing-go/ext"
+	"github.com/prometheus/client_golang/prometheus"
+
 	"github.com/beatlabs/patron/correlation"
 	"github.com/beatlabs/patron/encoding"
 	"github.com/beatlabs/patron/log"
 	"github.com/beatlabs/patron/reliability/circuitbreaker"
 	"github.com/beatlabs/patron/trace"
-	"github.com/opentracing-contrib/go-stdlib/nethttp"
-	opentracing "github.com/opentracing/opentracing-go"
-	"github.com/opentracing/opentracing-go/ext"
 )
 
 const (
 	clientComponent = "http-client"
 )
 
+var (
+	reqDurationMetrics *prometheus.HistogramVec
+)
+
+func init() {
+	reqDurationMetrics = prometheus.NewHistogramVec(
+		prometheus.HistogramOpts{
+			Namespace: "client",
+			Subsystem: "http",
+			Name:      "request_duration_seconds",
+			Help:      "HTTP requests completed by the client.",
+		},
+		[]string{"method", "url", "status_code"},
+	)
+	prometheus.MustRegister(reqDurationMetrics)
+}
+
 // Client interface of a HTTP client.
 type Client interface {
 	Do(ctx context.Context, req *http.Request) (*http.Response, error)
@@ -64,15 +84,22 @@ func (tc *TracedClient) Do(ctx context.Context, req *http.Request) (*http.Respon
 
 	req.Header.Set(correlation.HeaderID, correlation.IDFromContext(ctx))
 
+	start := time.Now()
+
 	rsp, err := tc.do(req)
+
+	ext.HTTPMethod.Set(ht.Span(), req.Method)
+	ext.HTTPUrl.Set(ht.Span(), req.URL.String())
+
 	if err != nil {
 		ext.Error.Set(ht.Span(), true)
-	} else {
-		ext.HTTPStatusCode.Set(ht.Span(), uint16(rsp.StatusCode))
+		return rsp, err
 	}
 
-	ext.HTTPMethod.Set(ht.Span(), req.Method)
-	ext.HTTPUrl.Set(ht.Span(), req.URL.String())
+	ext.HTTPStatusCode.Set(ht.Span(), uint16(rsp.StatusCode))
+	reqDurationMetrics.
+		WithLabelValues(req.Method, req.URL.Host, strconv.Itoa(rsp.StatusCode)).
+		Observe(time.Since(start).Seconds())
 
 	if hdr := req.Header.Get(encoding.AcceptEncodingHeader); hdr != "" {
 		rsp.Body = decompress(hdr, rsp)

client/http/http_test.go

@@ -12,12 +12,14 @@ import (
 	"testing"
 	"time"
 
-	"github.com/beatlabs/patron/encoding"
-	"github.com/beatlabs/patron/reliability/circuitbreaker"
-	opentracing "github.com/opentracing/opentracing-go"
+	"github.com/opentracing/opentracing-go"
 	"github.com/opentracing/opentracing-go/ext"
 	"github.com/opentracing/opentracing-go/mocktracer"
+	"github.com/prometheus/client_golang/prometheus/testutil"
 	"github.com/stretchr/testify/assert"
+
+	"github.com/beatlabs/patron/encoding"
+	"github.com/beatlabs/patron/reliability/circuitbreaker"
 )
 
 func TestTracedClient_Do(t *testing.T) {
@@ -40,6 +42,7 @@ func TestTracedClient_Do(t *testing.T) {
 	assert.NoError(t, err)
 	reqErr, err := http.NewRequest("GET", "", nil)
 	assert.NoError(t, err)
+	reqErr.Header.Set(encoding.AcceptEncodingHeader, "gzip")
 	opName := opName("GET", ts.URL)
 	opNameError := "HTTP GET"
 
@@ -48,16 +51,17 @@ func TestTracedClient_Do(t *testing.T) {
 		req *http.Request
 	}
 	tests := []struct {
-		name       string
-		args       args
-		wantErr    bool
-		wantOpName string
+		name        string
+		args        args
+		wantErr     bool
+		wantOpName  string
+		wantCounter int
 	}{
-		{name: "respose", args: args{c: c, req: req}, wantErr: false, wantOpName: opName},
-		{name: "response with circuit breaker", args: args{c: cb, req: req}, wantErr: false, wantOpName: opName},
-		{name: "respose with custom transport", args: args{c: ct, req: req}, wantErr: false, wantOpName: opName},
-		{name: "error", args: args{c: cb, req: reqErr}, wantErr: true, wantOpName: opNameError},
-		{name: "error with circuit breaker", args: args{c: cb, req: reqErr}, wantErr: true, wantOpName: opNameError},
+		{name: "response", args: args{c: c, req: req}, wantErr: false, wantOpName: opName, wantCounter: 1},
+		{name: "response with circuit breaker", args: args{c: cb, req: req}, wantErr: false, wantOpName: opName, wantCounter: 1},
+		{name: "response with custom transport", args: args{c: ct, req: req}, wantErr: false, wantOpName: opName, wantCounter: 1},
+		{name: "error", args: args{c: cb, req: reqErr}, wantErr: true, wantOpName: opNameError, wantCounter: 0},
+		{name: "error with circuit breaker", args: args{c: cb, req: reqErr}, wantErr: true, wantOpName: opNameError, wantCounter: 0},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
@@ -73,6 +77,9 @@ func TestTracedClient_Do(t *testing.T) {
 			assert.NotNil(t, sp)
 			assert.Equal(t, tt.wantOpName, sp.OperationName)
 			mtr.Reset()
+			// Test counters.
+			assert.Equal(t, tt.wantCounter, testutil.CollectAndCount(reqDurationMetrics))
+			reqDurationMetrics.Reset()
 		})
 	}
 }

go.mod

@@ -3,7 +3,6 @@ module github.com/beatlabs/patron
 require (
 	github.com/Shopify/sarama v1.28.0
 	github.com/aws/aws-sdk-go v1.36.15
-	github.com/cenkalti/backoff v2.2.1+incompatible // indirect
 	github.com/codahale/hdrhistogram v0.0.0-20161010025455-3a0bb77429bd // indirect
 	github.com/containerd/continuity v0.0.0-20200228182428-0f16d7a0959c // indirect
 	github.com/elastic/go-elasticsearch/v8 v8.0.0-20190731061900-ea052088db25