Add a configurable version of InstrumentHandler and InstrumentHandlerFunc.

Also, remove quotes from the Content-type header. It's not illegal to
have quotes there, but they are not needed, and at other places, we
are not using them. So fewer characters and more consistency.

Change-Id: If7a78bde85154163e4426daec493d973213e83e9

prometheus/http.go

@@ -20,45 +20,7 @@ import (
 	"time"
 )
 
-var (
+var instLabels = []string{"method", "code"}
-	instLabels = []string{"handler", "method", "code"}
-
-	reqCnt = NewCounterVec(
-		CounterOpts{
-			Subsystem: "http",
-			Name:      "requests_total",
-			Help:      "Total number of HTTP requests made.",
-		},
-		instLabels,
-	)
-
-	reqDur = NewSummaryVec(
-		SummaryOpts{
-			Subsystem: "http",
-			Name:      "request_duration_microseconds",
-			Help:      "The HTTP request latencies in microseconds.",
-		},
-		instLabels,
-	)
-
-	reqSz = NewSummaryVec(
-		SummaryOpts{
-			Subsystem: "http",
-			Name:      "request_size_bytes",
-			Help:      "The HTTP request sizes in bytes.",
-		},
-		instLabels,
-	)
-
-	resSz = NewSummaryVec(
-		SummaryOpts{
-			Subsystem: "http",
-			Name:      "response_size_bytes",
-			Help:      "The HTTP response sizes in bytes.",
-		},
-		instLabels,
-	)
-)
 
 type nower interface {
 	Now() time.Time
@@ -103,6 +65,71 @@ func InstrumentHandler(handlerName string, handler http.Handler) http.HandlerFun
 // (SummaryVec). Each has three labels: handler, method, code. The value of the
 // handler label is set by the handlerName parameter of this function.
 func InstrumentHandlerFunc(handlerName string, handlerFunc func(http.ResponseWriter, *http.Request)) http.HandlerFunc {
+	return InstrumentHandlerFuncWithOpts(
+		SummaryOpts{
+			Subsystem:   "http",
+			ConstLabels: Labels{"handler": handlerName},
+		},
+		handlerFunc,
+	)
+}
+
+// InstrumentHandlerWithOpts works like InstrumentHandler but provides more
+// flexibility (at the cost of a more complex call syntax). As
+// InstrumentHandler, this function registers four metric vector collectors, but
+// it uses the provided SummaryOpts to create them. However, the fields "Name"
+// and "Help" in the SummaryOpts are ignored. "Name" is replaced by
+// "requests_total", "request_duration_microseconds", "request_size_bytes", and
+// "response_size_bytes", respectively. "Help" is replaced by an appropriate
+// help string. The names of the variable labels of the vector collectors are
+// "method" (get, post, etc.), and "code" (HTTP status code).
+//
+// If InstrumentHandlerWithOpts is called as follows, it mimics exactly the
+// behavior of InstrumentHandler:
+//
+//     prometheus.InstrumentHandlerWithOpts(
+//         prometheus.SummaryOpts{
+//              Subsystem:   "http",
+//              ConstLabels: prometheus.Labels{"handler": handlerName},
+//         },
+//         handler,
+//     )
+//
+// Technical detail: "requests_total" is a CounterVec, not a SummaryVec, so it
+// cannot use SummaryOpts. Instead, a CounterOpts struct is created internally,
+// and all its fields are set to the equally named fields in the provided
+// SummaryOpts.
+func InstrumentHandlerWithOpts(opts SummaryOpts, handler http.Handler) http.HandlerFunc {
+	return InstrumentHandlerFuncWithOpts(opts, handler.ServeHTTP)
+}
+
+// InstrumentHandlerFuncWithOpts works like InstrumentHandlerFunc but provides
+// more flexibility (at the cost of a more complex call syntax). See
+// InstrumentHandlerWithOpts for details how the provided SummaryOpts are used.
+func InstrumentHandlerFuncWithOpts(opts SummaryOpts, handlerFunc func(http.ResponseWriter, *http.Request)) http.HandlerFunc {
+	reqCnt := NewCounterVec(
+		CounterOpts{
+			Namespace:   opts.Namespace,
+			Subsystem:   opts.Subsystem,
+			Name:        "requests_total",
+			Help:        "Total number of HTTP requests made.",
+			ConstLabels: opts.ConstLabels,
+		},
+		instLabels,
+	)
+
+	opts.Name = "request_duration_microseconds"
+	opts.Help = "The HTTP request latencies in microseconds."
+	reqDur := NewSummaryVec(opts, instLabels)
+
+	opts.Name = "request_size_bytes"
+	opts.Help = "The HTTP request sizes in bytes."
+	reqSz := NewSummaryVec(opts, instLabels)
+
+	opts.Name = "response_size_bytes"
+	opts.Help = "The HTTP response sizes in bytes."
+	resSz := NewSummaryVec(opts, instLabels)
+
 	regReqCnt := MustRegisterOrGet(reqCnt).(*CounterVec)
 	regReqDur := MustRegisterOrGet(reqDur).(*SummaryVec)
 	regReqSz := MustRegisterOrGet(reqSz).(*SummaryVec)
@@ -120,10 +147,10 @@ func InstrumentHandlerFunc(handlerName string, handlerFunc func(http.ResponseWri
 
 		method := sanitizeMethod(r.Method)
 		code := sanitizeCode(delegate.status)
-		regReqCnt.WithLabelValues(handlerName, method, code).Inc()
+		regReqCnt.WithLabelValues(method, code).Inc()
-		regReqDur.WithLabelValues(handlerName, method, code).Observe(elapsed)
+		regReqDur.WithLabelValues(method, code).Observe(elapsed)
-		regResSz.WithLabelValues(handlerName, method, code).Observe(float64(delegate.written))
+		regResSz.WithLabelValues(method, code).Observe(float64(delegate.written))
-		regReqSz.WithLabelValues(handlerName, method, code).Observe(float64(<-out))
+		regReqSz.WithLabelValues(method, code).Observe(float64(<-out))
 	})
 }
 

prometheus/http_test.go

@@ -37,15 +37,43 @@ func TestInstrumentHandler(t *testing.T) {
 	instant := time.Now()
 	end := instant.Add(30 * time.Second)
 	now = nowSeries(instant, end)
+	respBody := respBody("Howdy there!")
+
+	hndlr := InstrumentHandler("test-handler", respBody)
+
+	opts := SummaryOpts{
+		Subsystem:   "http",
+		ConstLabels: Labels{"handler": "test-handler"},
+	}
+
+	reqCnt := MustRegisterOrGet(NewCounterVec(
+		CounterOpts{
+			Namespace:   opts.Namespace,
+			Subsystem:   opts.Subsystem,
+			Name:        "requests_total",
+			Help:        "Total number of HTTP requests made.",
+			ConstLabels: opts.ConstLabels,
+		},
+		instLabels,
+	)).(*CounterVec)
+
+	opts.Name = "request_duration_microseconds"
+	opts.Help = "The HTTP request latencies in microseconds."
+	reqDur := MustRegisterOrGet(NewSummaryVec(opts, instLabels)).(*SummaryVec)
+
+	opts.Name = "request_size_bytes"
+	opts.Help = "The HTTP request sizes in bytes."
+	reqSz := MustRegisterOrGet(NewSummaryVec(opts, instLabels)).(*SummaryVec)
+
+	opts.Name = "response_size_bytes"
+	opts.Help = "The HTTP response sizes in bytes."
+	resSz := MustRegisterOrGet(NewSummaryVec(opts, instLabels)).(*SummaryVec)
+
 	reqCnt.Reset()
 	reqDur.Reset()
 	reqSz.Reset()
 	resSz.Reset()
 
-	respBody := respBody("Howdy there!")
-
-	hndlr := InstrumentHandler("test-handler", respBody)
-
 	resp := httptest.NewRecorder()
 	req := &http.Request{
 		Method: "GET",
@@ -63,7 +91,7 @@ func TestInstrumentHandler(t *testing.T) {
 	if want, got := 1, len(reqDur.children); want != got {
 		t.Errorf("want %d children in reqDur, got %d", want, got)
 	}
-	sum, err := reqDur.GetMetricWithLabelValues("test-handler", "get", "418")
+	sum, err := reqDur.GetMetricWithLabelValues("get", "418")
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -86,7 +114,7 @@ func TestInstrumentHandler(t *testing.T) {
 	if want, got := 1, len(reqCnt.children); want != got {
 		t.Errorf("want %d children in reqCnt, got %d", want, got)
 	}
-	cnt, err := reqCnt.GetMetricWithLabelValues("test-handler", "get", "418")
+	cnt, err := reqCnt.GetMetricWithLabelValues("get", "418")
 	if err != nil {
 		t.Fatal(err)
 	}

prometheus/registry.go

@@ -55,17 +55,17 @@ const (
 
 	// DelimitedTelemetryContentType is the content type set on telemetry
 	// data responses in delimited protobuf format.
-	DelimitedTelemetryContentType = `application/vnd.google.protobuf; proto="io.prometheus.client.MetricFamily"; encoding="delimited"`
+	DelimitedTelemetryContentType = `application/vnd.google.protobuf; proto=io.prometheus.client.MetricFamily; encoding=delimited`
 	// TextTelemetryContentType is the content type set on telemetry data
 	// responses in text format.
 	TextTelemetryContentType = `text/plain; version=` + APIVersion
 	// ProtoTextTelemetryContentType is the content type set on telemetry
 	// data responses in protobuf text format.  (Only used for debugging.)
-	ProtoTextTelemetryContentType = `application/vnd.google.protobuf; proto="io.prometheus.client.MetricFamily"; encoding="text"`
+	ProtoTextTelemetryContentType = `application/vnd.google.protobuf; proto=io.prometheus.client.MetricFamily; encoding=text`
 	// ProtoCompactTextTelemetryContentType is the content type set on
 	// telemetry data responses in protobuf compact text format.  (Only used
 	// for debugging.)
-	ProtoCompactTextTelemetryContentType = `application/vnd.google.protobuf; proto="io.prometheus.client.MetricFamily"; encoding="compact-text"`
+	ProtoCompactTextTelemetryContentType = `application/vnd.google.protobuf; proto=io.prometheus.client.MetricFamily; encoding=compact-text`
 
 	// Constants for object pools.
 	numBufs           = 4

prometheus/registry_test.go

@@ -266,7 +266,7 @@ metric: <
 			},
 			out: output{
 				headers: map[string]string{
-					"Content-Type": `application/vnd.google.protobuf; proto="io.prometheus.client.MetricFamily"; encoding="delimited"`,
+					"Content-Type": `application/vnd.google.protobuf; proto=io.prometheus.client.MetricFamily; encoding=delimited`,
 				},
 				body: []byte{},
 			},
@@ -289,7 +289,7 @@ metric: <
 			},
 			out: output{
 				headers: map[string]string{
-					"Content-Type": `application/vnd.google.protobuf; proto="io.prometheus.client.MetricFamily"; encoding="delimited"`,
+					"Content-Type": `application/vnd.google.protobuf; proto=io.prometheus.client.MetricFamily; encoding=delimited`,
 				},
 				body: expectedMetricFamilyAsBytes,
 			},
@@ -313,7 +313,7 @@ metric: <
 			},
 			out: output{
 				headers: map[string]string{
-					"Content-Type": `application/vnd.google.protobuf; proto="io.prometheus.client.MetricFamily"; encoding="delimited"`,
+					"Content-Type": `application/vnd.google.protobuf; proto=io.prometheus.client.MetricFamily; encoding=delimited`,
 				},
 				body: externalMetricFamilyAsBytes,
 			},
@@ -325,7 +325,7 @@ metric: <
 			},
 			out: output{
 				headers: map[string]string{
-					"Content-Type": `application/vnd.google.protobuf; proto="io.prometheus.client.MetricFamily"; encoding="delimited"`,
+					"Content-Type": `application/vnd.google.protobuf; proto=io.prometheus.client.MetricFamily; encoding=delimited`,
 				},
 				body: bytes.Join(
 					[][]byte{
@@ -386,7 +386,7 @@ metric: <
 			},
 			out: output{
 				headers: map[string]string{
-					"Content-Type": `application/vnd.google.protobuf; proto="io.prometheus.client.MetricFamily"; encoding="delimited"`,
+					"Content-Type": `application/vnd.google.protobuf; proto=io.prometheus.client.MetricFamily; encoding=delimited`,
 				},
 				body: bytes.Join(
 					[][]byte{
@@ -405,7 +405,7 @@ metric: <
 			},
 			out: output{
 				headers: map[string]string{
-					"Content-Type": `application/vnd.google.protobuf; proto="io.prometheus.client.MetricFamily"; encoding="text"`,
+					"Content-Type": `application/vnd.google.protobuf; proto=io.prometheus.client.MetricFamily; encoding=text`,
 				},
 				body: bytes.Join(
 					[][]byte{
@@ -424,7 +424,7 @@ metric: <
 			},
 			out: output{
 				headers: map[string]string{
-					"Content-Type": `application/vnd.google.protobuf; proto="io.prometheus.client.MetricFamily"; encoding="compact-text"`,
+					"Content-Type": `application/vnd.google.protobuf; proto=io.prometheus.client.MetricFamily; encoding=compact-text`,
 				},
 				body: bytes.Join(
 					[][]byte{