telemetry: add tracing

- telemetry/tace: add traces throughout code
- telemetry/metrics: nest metrics and trace under telemetry
- telemetry/tace: add service name span to HTTPMetricsHandler.
- telemetry/metrics: removed chain dependency middleware_tests.
- telemetry/metrics: wrap and encapsulate variatic view registration.
- telemetry/tace: add jaeger support for tracing.
- cmd/pomerium: move `parseOptions` to internal/config.
- cmd/pomerium: offload server handling to httputil and sub pkgs.
- httputil: standardize creation/shutdown of http listeners.
- httputil: prefer curve X25519 to P256 when negotiating TLS.
- fileutil: use standardized Getw

Signed-off-by: Bobby DeSimone <bobbydesimone@gmail.com>

internal/telemetry/metrics/providers_test.go

@@ -0,0 +1,29 @@
+package metrics // import "github.com/pomerium/pomerium/internal/telemetry/metrics"
+
+import (
+	"bytes"
+	"io/ioutil"
+	"net/http/httptest"
+	"regexp"
+	"testing"
+)
+
+func Test_PrometheusHandler(t *testing.T) {
+	h, err := PrometheusHandler()
+	if err != nil {
+		t.Fatal(err)
+	}
+	req := httptest.NewRequest("GET", "http://test.local/metrics", new(bytes.Buffer))
+	rec := httptest.NewRecorder()
+	h.ServeHTTP(rec, req)
+	resp := rec.Result()
+	b, _ := ioutil.ReadAll(resp.Body)
+
+	if resp == nil || resp.StatusCode != 200 {
+		t.Errorf("Metrics endpoint failed to respond: %s", b)
+	}
+
+	if m, _ := regexp.Match("^# HELP .*", b); !m {
+		t.Errorf("Metrics endpoint did not contain any help messages: %s", b)
+	}
+}