Add live mode toggle for real-time chart updates

Introduced a new "Live" button to enable real-time chart updates, refreshing data every second. Refactored data fetching to use `useRef` for `refresh` and updated styles for the live mode button, ensuring a seamless user experience.

frontend/src/pages/TargetDetailPage.jsx

@@ -1,4 +1,4 @@
-import React, { useEffect, useMemo, useState } from "react";
+import React, { useEffect, useMemo, useRef, useState } from "react";
 import { useParams } from "react-router-dom";
 import { Line, LineChart, ResponsiveContainer, Tooltip, XAxis, YAxis } from "recharts";
 import { apiFetch } from "../api";
@@ -68,6 +68,7 @@ export function TargetDetailPage() {
   const { id } = useParams();
   const { tokens, refresh, uiMode } = useAuth();
   const [range, setRange] = useState("1h");
+  const [liveMode, setLiveMode] = useState(false);
   const [series, setSeries] = useState({});
   const [locks, setLocks] = useState([]);
   const [activity, setActivity] = useState([]);
@@ -75,20 +76,27 @@ export function TargetDetailPage() {
   const [targetMeta, setTargetMeta] = useState(null);
   const [error, setError] = useState("");
   const [loading, setLoading] = useState(true);
+  const refreshRef = useRef(refresh);
+
+  useEffect(() => {
+    refreshRef.current = refresh;
+  }, [refresh]);
 
   useEffect(() => {
     let active = true;
-    (async () => {
-      setLoading(true);
+    const loadAll = async () => {
+      if (!series.connections?.length) {
+        setLoading(true);
+      }
       try {
         const [connections, xacts, cache, locksTable, activityTable, overviewData, targetInfo] = await Promise.all([
-          loadMetric(id, "connections_total", range, tokens, refresh),
-          loadMetric(id, "xacts_total", range, tokens, refresh),
-          loadMetric(id, "cache_hit_ratio", range, tokens, refresh),
-          apiFetch(`/targets/${id}/locks`, {}, tokens, refresh),
-          apiFetch(`/targets/${id}/activity`, {}, tokens, refresh),
-          apiFetch(`/targets/${id}/overview`, {}, tokens, refresh),
-          apiFetch(`/targets/${id}`, {}, tokens, refresh),
+          loadMetric(id, "connections_total", range, tokens, refreshRef.current),
+          loadMetric(id, "xacts_total", range, tokens, refreshRef.current),
+          loadMetric(id, "cache_hit_ratio", range, tokens, refreshRef.current),
+          apiFetch(`/targets/${id}/locks`, {}, tokens, refreshRef.current),
+          apiFetch(`/targets/${id}/activity`, {}, tokens, refreshRef.current),
+          apiFetch(`/targets/${id}/overview`, {}, tokens, refreshRef.current),
+          apiFetch(`/targets/${id}`, {}, tokens, refreshRef.current),
         ]);
         if (!active) return;
         setSeries({ connections, xacts, cache });
@@ -102,11 +110,36 @@ export function TargetDetailPage() {
       } finally {
         if (active) setLoading(false);
       }
-    })();
+    };
+
+    loadAll();
     return () => {
       active = false;
     };
-  }, [id, range, tokens, refresh]);
+  }, [id, range, tokens?.accessToken, tokens?.refreshToken]);
+
+  useEffect(() => {
+    if (!liveMode) return;
+    let active = true;
+    const intervalId = setInterval(async () => {
+      try {
+        const [connections, xacts, cache] = await Promise.all([
+          loadMetric(id, "connections_total", "15m", tokens, refreshRef.current),
+          loadMetric(id, "xacts_total", "15m", tokens, refreshRef.current),
+          loadMetric(id, "cache_hit_ratio", "15m", tokens, refreshRef.current),
+        ]);
+        if (!active) return;
+        setSeries({ connections, xacts, cache });
+      } catch {
+        // Keep previous chart values if a live tick fails.
+      }
+    }, 1000);
+
+    return () => {
+      active = false;
+      clearInterval(intervalId);
+    };
+  }, [liveMode, id, tokens?.accessToken, tokens?.refreshToken]);
 
   const chartData = useMemo(
     () => {
@@ -362,8 +395,28 @@ export function TargetDetailPage() {
         </div>
       )}
       <div className="range-picker">
+        <button
+          type="button"
+          className={`live-btn ${liveMode ? "active" : ""}`}
+          onClick={() => {
+            setLiveMode((prev) => {
+              const next = !prev;
+              if (next) setRange("15m");
+              return next;
+            });
+          }}
+        >
+          LIVE
+        </button>
         {Object.keys(ranges).map((r) => (
-          <button key={r} onClick={() => setRange(r)} className={r === range ? "active" : ""}>
+          <button
+            key={r}
+            onClick={() => {
+              setLiveMode(false);
+              setRange(r);
+            }}
+            className={r === range ? "active" : ""}
+          >
             {r}
           </button>
         ))}