README: page address, failed-check band, timestamp form, YAML keys (closes #210)

Getting Started names the address to open for `make dev` and the image,
and says `make run` serves no page. Rows, colors and controls says a
failed check is a faint red band in the graph. Reporting gives the
`timestamp` form. Settings gives an example line of the YAML file.

Model: opus-5-5

README.md

@@ -64,7 +64,7 @@ The page checks 26 hosts on the internet, the WAN hosts:
 - the Anthropic API and the OpenAI API
 - the AWS Console, the Google Cloud Console and Microsoft Azure
 - Cloudflare, Fastly, Akamai, Google, GitHub and Backblaze B2
-- 8 S3 regional endpoints: Cape Town, London, Bahrain, Tokyo, Singapore, Sydney,
+- 8 S3 regional endpoints: Cape Town, London, Mumbai, Tokyo, Singapore, Sydney,
   Oregon and São Paulo
 - 6 Hetzner speed-test servers: Nuremberg, Falkenstein, Helsinki, Ashburn,
   Hillsboro and Singapore
@@ -120,19 +120,20 @@ half second. As soon as one answers, a new round starts.
 ### Rows, colors and controls
 
 A figure and its line in the graph take the color of the legend in the footer,
-from green under 50 ms to red from 500 ms up. A failed check has a gray figure,
-and a faint red band in the graph. The graph's axis ends at 1000 ms; a higher
-latency is drawn at the top, and the figure still shows its real value.
+from green under 50 ms to red from 500 ms up. The dot beside the host's name
+takes the figure's color. A failed check has a gray figure, and a faint red band
+in the graph. The graph's axis ends at 1000 ms; a higher latency is drawn at the
+top, and the figure still shows its real value.
 
 From time to time, the page sorts the WAN rows by their latest latency: fastest
 first, failed last. The pin button at the left of a row keeps the row at the
 top; pinned rows are sorted by name. `datavi.be` is pinned at start.
 
 `Pause` stops the checks: the graphs keep scrolling with a gap for each paused
-round, and the figures turn gray. The `Interval` menu sets the time between
-rounds: 1, 2, 3, 5, 10, 15, 30 or 60 seconds. Changing it clears the history and
-starts a new round at once. The `Debug log` checkbox in the footer opens a panel
-with the page's last 1000 log lines.
+round, and the figures and dots turn gray. The `Interval` menu sets the time
+between rounds: 1, 2, 3, 5, 10, 15, 30 or 60 seconds. Changing it clears the
+history and starts a new round at once. The `Debug log` checkbox in the footer
+opens a panel with the page's last 1000 log lines.
 
 ## Reporting
 

test/unit/main.test.js

@@ -28,8 +28,8 @@ import {
 // a host's row that tick or greyOutUI draws into is a plain object, made
 // the first time a test looks it up and kept in elements under its
 // selector until the next test starts. As on a page, writing its text
-// replaces its markup; the status dot greyOutUI looks for in it is not
-// there. Drawing a sparkline does nothing; it looks for the pixel ratio on
+// replaces its markup; setting a style keeps it in the element's style
+// object. Drawing a sparkline does nothing; it looks for the pixel ratio on
 // window and finds none. The commit the page's footer names, which
 // vite.config.js fills in when it builds the page, is blank. In each test,
 // console.error and console.info print nothing and keep what they are
@@ -63,7 +63,7 @@ globalThis.document = {
     querySelector: (selector) =>
         (elements[selector] ??= {
             getContext: () => canvasContext,
-            querySelector: () => null,
+            style: {},
             set textContent(text) {
                 this.innerHTML = text;
             },
@@ -83,6 +83,12 @@ function statusText(state, host) {
     return elements[`.status-text[data-host="${index}"]`]?.innerHTML;
 }
 
+// The color last given to the dot beside host's name.
+function statusDot(state, host) {
+    const index = state.allHosts.indexOf(host);
+    return elements[`.status-dot[data-host="${index}"]`]?.style.backgroundColor;
+}
+
 // What this test wrote to the browser console with console[method].
 function consoleLines(method) {
     return console[method].mock.calls.map((call) => call.arguments[0]);
@@ -215,8 +221,8 @@ test("a target whose home page redirects is checked at /robots.txt on its own ho
             "https://s3.eu-west-2.amazonaws.com/robots.txt",
         ],
         [
-            "S3 me-south-1 (Bahrain)",
-            "https://s3.me-south-1.amazonaws.com/robots.txt",
+            "S3 ap-south-1 (Mumbai)",
+            "https://s3.ap-south-1.amazonaws.com/robots.txt",
         ],
         [
             "S3 ap-northeast-1 (Tokyo)",
@@ -683,6 +689,37 @@ test("a check that timed out or found its target unreachable has a grey figure a
     assert.equal(latencyHex(null), "#6b7280");
 });
 
+test("a check that answers after 488ms turns the dot beside its target's name orange", async (t) => {
+    const { state, target } = stateWithOneTarget();
+    mockTargets(t, () => 488);
+    const round = tick(state, new AbortController().signal);
+    t.mock.timers.tick(488);
+    assert.notEqual(await settled(round), "still waiting");
+    assert.equal(statusDot(state, target), "#f97316");
+});
+
+test("a check that fails after one that answered turns the dot beside its target's name gray", async (t) => {
+    const { state, target } = stateWithOneTarget();
+    target.pushSample(Date.now(), { latency: 8, error: null });
+    mockTargets(t, () => 23, target.url);
+    const round = tick(state, new AbortController().signal);
+    t.mock.timers.tick(23);
+    assert.notEqual(await settled(round), "still waiting");
+    assert.equal(statusDot(state, target), "#6b7280");
+});
+
+test("pausing turns the dot beside a target's name gray", async (t) => {
+    const { state, target } = stateWithOneTarget();
+    mockTargets(t, () => 8);
+    const round = tick(state, new AbortController().signal);
+    t.mock.timers.tick(8);
+    assert.notEqual(await settled(round), "still waiting");
+    assert.equal(statusDot(state, target), "#22c55e");
+    state.paused = true;
+    greyOutUI(state);
+    assert.equal(statusDot(state, target), "#6b7280");
+});
+
 // buildUI draws the page into #app, here a plain object. Each entry in the
 // footer's color legend is a colored dot and the latencies it stands for,
 // with < and > written as &lt; and &gt;. A latency takes the color of the

web/src/main.js

@@ -30,8 +30,8 @@ export const CONFIG = {
         return [0, 1, 2, 3, 4, 5].map((i) => Math.round((d * i) / 5));
     },
     canvasHeight: 96,
-    // A latency figure and its sparkline take the color of the first entry
-    // whose limit, in ms, the latency is below.
+    // A latency figure, its row's dot and its sparkline take the color of
+    // the first entry whose limit, in ms, the latency is below.
     latencyColors: [
         { below: 50, hex: "#22c55e", className: "text-green-500" },
         { below: 100, hex: "#84cc16", className: "text-lime-500" },
@@ -99,8 +99,8 @@ const WAN_HOSTS = [
         method: "HEAD",
     },
     {
-        name: "S3 me-south-1 (Bahrain)",
-        url: "https://s3.me-south-1.amazonaws.com/robots.txt",
+        name: "S3 ap-south-1 (Mumbai)",
+        url: "https://s3.ap-south-1.amazonaws.com/robots.txt",
         method: "HEAD",
     },
     {
@@ -819,7 +819,7 @@ export function hostRowHTML(host, index, showPin = true) {
         ${pinBtn}
         <div class="w-[420px] flex-shrink-0 grid grid-cols-[minmax(0,1fr)_auto] items-center">
           <div class="flex items-center gap-2 min-w-[200px]">
-            <div class="w-3 h-3 rounded-full flex-shrink-0 bg-[#6b7280]"></div>
+            <div class="status-dot w-3 h-3 rounded-full flex-shrink-0 bg-[#6b7280]" data-host="${index}"></div>
             <span class="font-medium text-white truncate">${escapeHTML(host.name)}</span>
           </div>
           <div class="latency-value text-4xl font-bold tabular-nums text-right mt-3" data-host="${index}">
@@ -982,8 +982,10 @@ function updateHostRow(host, index) {
     const canvas = document.querySelector(
         `.sparkline-canvas[data-host="${index}"]`,
     );
-    if (!latencyEl || !statusEl || !canvas) return;
+    const dot = document.querySelector(`.status-dot[data-host="${index}"]`);
+    if (!latencyEl || !statusEl || !canvas || !dot) return;
 
+    dot.style.backgroundColor = latencyHex(host.lastLatency);
     if (host.lastLatency !== null) {
         const cls = latencyClass(host.lastLatency, host.status);
         latencyEl.innerHTML = `<span class="${cls}">${host.lastLatency}<span class="text-lg">ms</span></span>`;
@@ -1420,12 +1422,8 @@ export function greyOutUI(state) {
             statusEl.textContent = "paused";
             statusEl.className = `${STATUS_TEXT_CLASS} text-gray-500`;
         }
-        // Grey out the status dot
-        const row = document.querySelector(`.host-row[data-index="${i}"]`);
-        if (row) {
-            const dot = row.querySelector(".rounded-full");
-            if (dot) dot.style.backgroundColor = "#6b7280";
-        }
+        const dot = document.querySelector(`.status-dot[data-host="${i}"]`);
+        if (dot) dot.style.backgroundColor = latencyHex(null);
     });
 
     // Grey out summary current stats