More succd into succbone subdirectory

succbone/succd/http.go

@@ -0,0 +1,121 @@
+package main
+
+import (
+	_ "embed"
+	"fmt"
+	"html/template"
+	"net/http"
+	_ "net/http/pprof"
+	"os"
+	"strings"
+	"time"
+
+	"github.com/coder/websocket"
+	"github.com/coder/websocket/wsjson"
+	"k8s.io/klog"
+)
+
+var (
+	//go:embed index.html
+	templateIndexText string
+	templateIndex     = template.Must(template.New("index").Parse(templateIndexText))
+)
+
+func formatVolts(v float32) string {
+	return fmt.Sprintf("%.4f V", v)
+}
+
+// formatMbar formats a millibar value using scientific notation and returns a
+// HTML fragment (for superscript support).
+func formatMbar(v float32) template.HTML {
+	exp := 0
+	for v < 1 {
+		v *= 10
+		exp -= 1
+	}
+	for v >= 10 {
+		v /= 10
+		exp += 1
+	}
+	res := fmt.Sprintf("%.3f", v)
+	res += fmt.Sprintf(" x 10<sup>%d</sup>", exp)
+	res += " mbar"
+	return template.HTML(res)
+}
+
+// httpIndex is the / view.
+func (d *daemon) httpIndex(w http.ResponseWriter, r *http.Request) {
+	if r.URL.Path != "/" {
+		http.NotFound(w, r)
+		return
+	}
+
+	volts, mbar := d.pirani()
+
+	loadB, err := os.ReadFile("/proc/loadavg")
+	load := "unknown"
+	if err == nil {
+		parts := strings.Fields(string(loadB))
+		load = strings.Join(parts[:3], " ")
+	}
+
+	hostname, err := os.Hostname()
+	if err != nil {
+		hostname = "unknown"
+	}
+
+	templateIndex.Execute(w, map[string]any{
+		"volts":    formatVolts(volts),
+		"mbar":     formatMbar(mbar),
+		"hostname": hostname,
+		"load":     load,
+	})
+}
+
+// httpStream is the websocket clientwards data hose, returning a 10Hz update
+// stream of pressure/voltage.
+func (d *daemon) httpStream(w http.ResponseWriter, r *http.Request) {
+	c, err := websocket.Accept(w, r, nil)
+	if err != nil {
+		return
+	}
+	defer c.CloseNow()
+
+	t := time.NewTicker(time.Second / 10)
+	defer t.Stop()
+
+	ctx := c.CloseRead(r.Context())
+	for {
+		select {
+		case <-ctx.Done():
+			c.Close(websocket.StatusNormalClosure, "")
+			return
+		case <-t.C:
+			// TODO(q3k): don't poll, get notified when new ADC readout is available.
+			volts, mbar := d.pirani()
+			v := struct {
+				Volts     string
+				Mbar      string
+				MbarFloat float32
+			}{
+				Volts:     formatVolts(volts),
+				Mbar:      string(formatMbar(mbar)),
+				MbarFloat: mbar,
+			}
+			if err := wsjson.Write(ctx, c, v); err != nil {
+				klog.Errorf("Websocket write failed: %v", err)
+				return
+			}
+		}
+	}
+}
+
+// httpMetrics serves minimalistic Prometheus-compatible metrics.
+func (d *daemon) httpMetrics(w http.ResponseWriter, r *http.Request) {
+	// TODO(q3k): also serve Go stuff using the actual Prometheus metrics client
+	// library.
+	_, mbar := d.pirani()
+	fmt.Fprintf(w, "# HELP sem_pressure_mbar Pressure in the SEM chamber, in millibar\n")
+	fmt.Fprintf(w, "# TYPE sem_pressure_mbar gauge\n")
+	fmt.Fprintf(w, "sem_pressure_mbar %f\n", mbar)
+}