Initial work on rapl-daemon. Initial server set up. API to read max power per zone and API to write new power cap have both been written.

rapl-daemon/main.go

@@ -0,0 +1,49 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"html"
+	"log"
+	"net/http"
+)
+
+const powercapDir = "/sys/class/powercap/"
+
+// Cap is a payload that is expected from Elektron to cap a node
+type Cap struct {
+	Percentage int
+}
+
+func main() {
+	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
+		fmt.Fprintf(w, "Unsupported endpoint %s", html.EscapeString(r.URL.Path))
+	})
+
+	http.HandleFunc("/powercap", powercapEndpoint)
+	log.Fatal(http.ListenAndServe(":9090", nil))
+}
+
+// Handler powercapping HTTP API endpoint
+func powercapEndpoint(w http.ResponseWriter, r *http.Request) {
+	var payload Cap
+	decoder := json.NewDecoder(r.Body)
+	err := decoder.Decode(&payload)
+	if err != nil {
+		http.Error(w, "Error parsing payload: "+err.Error(), 400)
+		return
+	}
+
+	if payload.Percentage < 0 || payload.Percentage > 100 {
+		http.Error(w, "Bad payload: percentage must be between 0 and 100", 400)
+		return
+	}
+
+	err = capNode(powercapDir, payload.Percentage)
+	if err != nil {
+		http.Error(w, err.Error(), 400)
+		return
+	}
+
+	fmt.Fprintf(w, "Capped node at %d percent", payload.Percentage)
+}