Merge pull request #12 from bweston92/feature/status-code-extractor

Add status code extractor.

client.go

@@ -11,6 +11,10 @@ import (
 	"github.com/prometheus/client_golang/prometheus"
 )
 
+const (
+	BogusStatusCode = 999
+)
+
 // Transport is a http.RoundTripper that collects Prometheus metrics of every
 // request it processes. It allows to be configured with callbacks that process
 // request path and query into a suitable label value.
@@ -23,6 +27,7 @@ type Transport struct {
 type Callbacks struct {
 	PathProcessor  func(string) string
 	QueryProcessor func(string) string
+	CodeProcessor  func(int) string
 }
 
 const (
@@ -52,6 +57,15 @@ var (
 		parts := strings.Split(path, "/")
 		return parts[len(parts)-1]
 	}
+	// IntToStringProcessor converts an integer value to its string representation.
+	IntToStringProcessor = func(input int) string { return fmt.Sprintf("%d", input) }
+	// ServerErrorCodeProcessor exports all failed responses (5xx, timeouts, ...) as status=failure
+	ServerErrorCodeProcessor = func(code int) string {
+		if code >= http.StatusInternalServerError {
+			return "failure"
+		}
+		return "success"
+	}
 )
 
 // init registers the Prometheus metric globally when the package is loaded.
@@ -62,7 +76,7 @@ func init() {
 // RoundTrip implements http.RoundTripper. It forwards the request to the
 // next RoundTripper and measures the time it took in Prometheus summary.
 func (it *Transport) RoundTrip(req *http.Request) (*http.Response, error) {
-	var statusCode int
+	statusCode := BogusStatusCode
 
 	// Remember the current time.
 	now := time.Now()
@@ -80,7 +94,7 @@ func (it *Transport) RoundTrip(req *http.Request) (*http.Response, error) {
 		it.cbs.PathProcessor(req.URL.Path),
 		it.cbs.QueryProcessor(req.URL.RawQuery),
 		req.Method,
-		fmt.Sprintf("%d", statusCode),
+		it.cbs.CodeProcessor(statusCode),
 	).Observe(time.Since(now).Seconds())
 
 	// return the response and error reported from the next RoundTripper.
@@ -123,6 +137,10 @@ func NewTransport(next http.RoundTripper, cbs *Callbacks) http.RoundTripper {
 	if cbs.QueryProcessor == nil {
 		cbs.QueryProcessor = EliminatingProcessor
 	}
+	// By default, status code is set as is.
+	if cbs.CodeProcessor == nil {
+		cbs.CodeProcessor = IntToStringProcessor
+	}
 
 	return &Transport{next: next, cbs: cbs}
 }

examples/status-code/main.go

@@ -0,0 +1,54 @@
+package main
+
+import (
+	"fmt"
+	"log"
+	"net/http"
+	"time"
+
+	"github.com/linki/instrumented_http"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
+)
+
+func main() {
+	go func() {
+		http.Handle("/metrics", promhttp.Handler())
+		log.Fatal(http.ListenAndServe("127.0.0.1:9099", nil))
+	}()
+
+	client := instrumented_http.NewClient(nil, &instrumented_http.Callbacks{
+		PathProcessor:  instrumented_http.IdentityProcessor,
+		QueryProcessor: instrumented_http.IdentityProcessor,
+		CodeProcessor: func(code int) string {
+			// export all status codes >= 400 as label status=failure instead of their individual values.
+			if code >= http.StatusBadRequest {
+				return "failure"
+			}
+			return "success"
+		},
+	})
+
+	for {
+		func() {
+			resp, err := client.Get("https://kubernetes.io/docs/search/?q=pods")
+			if err != nil {
+				log.Fatal(err)
+			}
+			defer resp.Body.Close()
+
+			fmt.Printf("%d\n", resp.StatusCode)
+		}()
+
+		time.Sleep(10 * time.Second)
+	}
+}
+
+// expected result:
+//
+// $ curl -Ss 127.0.0.1:9099/metrics | grep http
+//
+// http_request_duration_seconds{handler="instrumented_http",host="kubernetes.io",method="GET",path="/docs/search/",query="q=pods",scheme="https",status="success",quantile="0.5"} 0.662351
+// http_request_duration_seconds{handler="instrumented_http",host="kubernetes.io",method="GET",path="/docs/search/",query="q=pods",scheme="https",status="success",quantile="0.9"} 1.000437
+// http_request_duration_seconds{handler="instrumented_http",host="kubernetes.io",method="GET",path="/docs/search/",query="q=pods",scheme="https",status="success",quantile="0.99"} 1.000437
+// http_request_duration_seconds_sum{handler="instrumented_http",host="kubernetes.io",method="GET",path="/docs/search/",query="q=pods",scheme="https",status="success"} 1.662788442
+// http_request_duration_seconds_count{handler="instrumented_http",host="kubernetes.io",method="GET",path="/docs/search/",query="q=pods",scheme="https",status="success"} 2