Add redux actions/reducer for metrics

metrics_handler.go

@@ -0,0 +1,52 @@
+package asynqmon
+
+import (
+	"fmt"
+	"io"
+	"net/http"
+	"net/url"
+	"strconv"
+	"strings"
+	"time"
+)
+
+type getMetricsResponse struct {
+	// TODO
+}
+
+func unixTimeString(t time.Time) string {
+	return strconv.Itoa(int(t.Unix()))
+}
+
+func newGetMetricsHandlerFunc(client *http.Client) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		const (
+			baseAddr = "http://localhost:9090"
+			apiPath  = "/api/v1/query_range"
+			promQL   = "asynq_tasks_enqueued_total"
+		)
+		var b strings.Builder
+		v := url.Values{}
+		b.WriteString(baseAddr)
+		b.WriteString(apiPath)
+		v.Add("query", promQL)
+		now := time.Now()
+		v.Add("start", unixTimeString(now.Add(-30*time.Minute)))
+		v.Add("end", unixTimeString(now))
+		v.Add("step", (1 * time.Minute).String())
+		b.WriteString("?")
+		b.WriteString(v.Encode())
+		url := b.String()
+		fmt.Printf("DEBUG: url: %s\n", url)
+		resp, err := client.Get(url)
+		if err != nil {
+			http.Error(w, fmt.Sprintf("request failed: GET %q: %v", url, err), http.StatusInternalServerError)
+			return
+		}
+		defer resp.Body.Close()
+		if _, err := io.Copy(w, resp.Body); err != nil {
+			http.Error(w, fmt.Sprintf("failed to copy: %v", err), http.StatusInternalServerError)
+			return
+		}
+	}
+}