More succd into succbone subdirectory

succbone/succd/main.go

@@ -0,0 +1,124 @@
+package main
+
+import (
+	"context"
+	"errors"
+	"flag"
+	"fmt"
+	"math"
+	"net/http"
+	"os"
+	"os/signal"
+	"sync"
+	"time"
+
+	"k8s.io/klog"
+)
+
+// daemon is the main state of the succdaemon.
+type daemon struct {
+	// adcPirani is the adc implementation returning the voltage of the Pfeiffer
+	// Pirani gauge.
+	adcPirani adc
+
+	// mu guards state variables below.
+	mu sync.RWMutex
+	// adcPiraniVolts is a moving window of read ADC values, used to calculate a
+	// moving average.
+	adcPiraniVolts []float32
+}
+
+// process runs the pain acquisition and control loop of succd.
+func (d *daemon) process(ctx context.Context) {
+	ticker := time.NewTicker(time.Millisecond * 100)
+	defer ticker.Stop()
+	for {
+		select {
+		case <-ticker.C:
+			if err := d.processOnce(ctx); err != nil {
+				if errors.Is(err, ctx.Err()) {
+					return
+				} else {
+					klog.Errorf("Processing error: %v", err)
+					time.Sleep(time.Second * 10)
+				}
+			}
+		case <-ctx.Done():
+			return
+		}
+	}
+}
+
+// processOnce runs the main loop step of succd.
+func (d *daemon) processOnce(_ context.Context) error {
+	v, err := d.adcPirani.Read()
+	if err != nil {
+		return fmt.Errorf("when reading ADC: %w", err)
+	}
+	d.mu.Lock()
+	d.adcPiraniVolts = append(d.adcPiraniVolts, v)
+	trim := len(d.adcPiraniVolts) - 100
+	if trim > 0 {
+		d.adcPiraniVolts = d.adcPiraniVolts[trim:]
+	}
+	d.mu.Unlock()
+
+	return nil
+}
+
+// pirani returns the Pirani gauge voltage and pressure.
+func (d *daemon) pirani() (volts float32, mbar float32) {
+	d.mu.RLock()
+	volts = 0.0
+	for _, v := range d.adcPiraniVolts {
+		volts += v
+	}
+	if len(d.adcPiraniVolts) != 0 {
+		volts /= float32(len(d.adcPiraniVolts))
+	}
+	d.mu.RUnlock()
+
+	// Per Pirani probe docs.
+	bar := math.Pow(10.0, float64(volts)-8.5)
+	mbar = float32(bar * 1000.0)
+	return
+}
+
+var (
+	flagFake       bool
+	flagListenHTTP string
+)
+
+func main() {
+	flag.BoolVar(&flagFake, "fake", false, "Enable fake mode which allows to run succd for tests outside the succbone")
+	flag.StringVar(&flagListenHTTP, "listen_http", ":8080", "Address at which to listen for HTTP requests")
+	flag.Parse()
+
+	ctx, _ := signal.NotifyContext(context.Background(), os.Interrupt)
+
+	d := daemon{}
+	if flagFake {
+		klog.Infof("Starting with fake Pirani probe")
+		d.adcPirani = &fakeADC{}
+	} else {
+		adc, err := newBBADC(0)
+		if err != nil {
+			klog.Exitf("Failed to setup Pirani ADC: %v", err)
+		}
+		d.adcPirani = adc
+	}
+
+	http.HandleFunc("/", d.httpIndex)
+	http.HandleFunc("/stream", d.httpStream)
+	http.HandleFunc("/metrics", d.httpMetrics)
+
+	klog.Infof("Listening for HTTP at %s", flagListenHTTP)
+	go func() {
+		if err := http.ListenAndServe(flagListenHTTP, nil); err != nil {
+			klog.Errorf("HTTP listen failed: %v", err)
+		}
+	}()
+
+	go d.process(ctx)
+	<-ctx.Done()
+}