common/http: rename to common/httpserver

This is a preparation to introduce an httpclient common package. And it
makes it easier to use http from the standard library.

common/httpserver/metrics.go

@@ -0,0 +1,56 @@
+// SPDX-FileCopyrightText: 2022 Free Mobile
+// SPDX-License-Identifier: AGPL-3.0-only
+
+package httpserver
+
+import "akvorado/common/reporter"
+
+type metrics struct {
+	inflights reporter.Gauge
+	requests  *reporter.CounterVec
+	durations *reporter.HistogramVec
+	sizes     *reporter.HistogramVec
+	cacheHit  *reporter.CounterVec
+	cacheMiss *reporter.CounterVec
+}
+
+func (c *Component) initMetrics() {
+	c.metrics.inflights = c.r.Gauge(
+		reporter.GaugeOpts{
+			Name: "inflight_requests",
+			Help: "Number of requests currently being served by the HTTP server.",
+		},
+	)
+	c.metrics.requests = c.r.CounterVec(
+		reporter.CounterOpts{
+			Name: "requests_total",
+			Help: "Number of requests handled by an handler.",
+		}, []string{"handler", "code", "method"},
+	)
+	c.metrics.durations = c.r.HistogramVec(
+		reporter.HistogramOpts{
+			Name:    "request_duration_seconds",
+			Help:    "Latencies for served requests.",
+			Buckets: []float64{.25, .5, 1, 2.5, 5, 10},
+		}, []string{"handler", "method"},
+	)
+	c.metrics.sizes = c.r.HistogramVec(
+		reporter.HistogramOpts{
+			Name:    "response_size_bytes",
+			Help:    "Response sizes for requests.",
+			Buckets: []float64{200, 500, 1000, 1500, 5000},
+		}, []string{"handler", "method"},
+	)
+	c.metrics.cacheHit = c.r.CounterVec(
+		reporter.CounterOpts{
+			Name: "cache_hit_total",
+			Help: "Number of requests served from cache",
+		}, []string{"path", "method"},
+	)
+	c.metrics.cacheMiss = c.r.CounterVec(
+		reporter.CounterOpts{
+			Name: "cache_miss_total",
+			Help: "Number of requests not served from cache",
+		}, []string{"path", "method"},
+	)
+}