Replace unused server metrics with a count (Refs #139)

src/lib/metrics.ts

@@ -50,12 +50,6 @@ export interface Utilization {
     playerHours: number;
 }
 
-export interface ServerMetrics extends Utilization {
-    server: string;
-    /** A current registration with this name exists; historical identity may differ. */
-    currentRegistered: boolean;
-}
-
 export interface MatchMetrics {
     /** Retained matches whose recorded start is within the selected window. */
     started: number;
@@ -153,7 +147,8 @@ export interface MetricsData {
     scopeLatestSampleAt: number | null;
     summary: Utilization;
     running: RunningMetrics;
-    servers: ServerMetrics[];
+    /** Distinct recorded names sampled in this scope/window, including zero elapsed time. */
+    sampledServerCount: number;
     matches: MatchMetrics;
     maps: MapMetrics[];
     points: MetricPoint[];

src/lib/server/fleet/metrics.ts

@@ -13,7 +13,6 @@ import {
     type MetricsQuery,
     type PreviousMetrics,
     type RunningMetrics,
-    type ServerMetrics,
     type Utilization
 } from '../../metrics.js';
 
@@ -191,17 +190,13 @@ export function readMetrics(input: MetricsDays | MetricsQuery, now = Date.now())
         );
     const globalBounds = evidenceBounds(groups);
     const scopedBounds = evidenceBounds(groups.filter(matchesScope));
-    const registered = new Set(
-        (
-            handle.prepare('SELECT name FROM servers WHERE destroyed_at IS NULL').all() as {
-                name: string;
-            }[]
-        ).map((server) => server.name)
-    );
+    const registered = handle
+        .prepare('SELECT COUNT(*) AS count FROM servers WHERE destroyed_at IS NULL')
+        .get() as { count: number };
     const metadata = {
         firstRetainedSampleAt: globalBounds.first,
         latestSampleAt: globalBounds.latest,
-        registeredServerCount: registered.size,
+        registeredServerCount: registered.count,
         scopeFirstSampleAt: scopedBounds.first,
         scopeLatestSampleAt: scopedBounds.latest
     };
@@ -236,7 +231,7 @@ export function readMetrics(input: MetricsDays | MetricsQuery, now = Date.now())
         lastSampleAt: null,
         partialHistory: false
     };
-    const serverTotals = new Map<string, ServerMetrics>();
+    const sampledServers = new Set<string>();
     const mapTotals = new Map<string, Map<string, MapMetrics>>();
     function mapFor(gameName: string, label: string): MapMetrics {
         let game = mapTotals.get(gameName);
@@ -401,8 +396,8 @@ export function readMetrics(input: MetricsDays | MetricsQuery, now = Date.now())
             for (const sample of samples)
                 addObservation(previous.summary, sample.players, priorHours);
         }
-        // Preserve current-window zero-duration rows without bringing rows from
-        // the separate comparison window into the visible server/map tables.
+        // Preserve current-window zero-duration evidence without bringing samples
+        // from the separate comparison window into the current count or map table.
         if (at < since - ONLINE_MAX_MS) return;
         const start = Math.max(at, since);
         const hours = Math.max(0, end - start) / 3600_000;
@@ -425,18 +420,9 @@ export function readMetrics(input: MetricsDays | MetricsQuery, now = Date.now())
             cursor = stop;
         }
         for (const sample of samples) {
-            let server = serverTotals.get(sample.server);
-            if (!server) {
-                server = {
-                    server: sample.server,
-                    currentRegistered: registered.has(sample.server),
-                    ...emptyUtilization()
-                };
-                serverTotals.set(sample.server, server);
-            }
+            sampledServers.add(sample.server);
             const map = mapFor(sample.game, sample.map);
             addObservation(summary, sample.players, hours);
-            addObservation(server, sample.players, hours);
             addObservation(map, sample.players, hours);
             for (const slice of slices) addObservation(slice.point, sample.players, slice.hours);
             if (sample.players === null) counts.unknown++;
@@ -493,9 +479,6 @@ export function readMetrics(input: MetricsDays | MetricsQuery, now = Date.now())
     }
     aggregateBatch(now);
 
-    const servers = [...serverTotals.values()].sort(
-        (a, b) => b.active - a.active || compareText(a.server, b.server)
-    );
     const maps = [...mapTotals.values()]
         .flatMap((game) => [...game.values()])
         .sort(
@@ -531,7 +514,7 @@ export function readMetrics(input: MetricsDays | MetricsQuery, now = Date.now())
         summary,
         running,
         matches: matchMetrics(totalMatches),
-        servers,
+        sampledServerCount: sampledServers.size,
         maps,
         points,
         previous,

src/lib/ui/metrics-refresh.ts

@@ -63,6 +63,8 @@ function validReport(value: unknown): value is MetricsData {
         return false;
     if (
         !numeric(value.registeredServerCount) ||
+        !nonnegative(value.sampledServerCount) ||
+        !Number.isInteger(value.sampledServerCount) ||
         typeof value.autoscalingPaused !== 'boolean' ||
         ![
             'firstRetainedSampleAt',
@@ -107,17 +109,6 @@ function validReport(value: unknown): value is MetricsData {
         )
     )
         return false;
-    if (
-        !Array.isArray(value.servers) ||
-        !value.servers.every(
-            (item) =>
-                record(item) &&
-                totals(item) &&
-                typeof item.server === 'string' &&
-                typeof item.currentRegistered === 'boolean'
-        )
-    )
-        return false;
     if (
         !record(value.previous) ||
         !totals(value.previous.summary) ||

src/routes/metrics/+page.svelte

@@ -257,14 +257,14 @@
             <EmptyState
                 title={report.latestSampleAt === null
                     ? 'No retained observations yet'
-                    : report.servers.length > 0
+                    : report.sampledServerCount > 0
                       ? 'Waiting for observed time'
                       : 'No captured time in this scope'}
                 description={report.latestSampleAt === null
                     ? report.registeredServerCount > 0
                         ? 'Leave the manager running to collect server status and build a history.'
                         : 'Register a server to begin collecting utilization history.'
-                    : report.servers.length > 0
+                    : report.sampledServerCount > 0
                       ? 'Captured samples have no elapsed time in this window. Time builds between status checks.'
                       : 'There are no elapsed observations for the selected game, map, and time window. Try another scope or a wider range.'}
             >

tests/unit/metrics-refresh.test.ts

@@ -19,7 +19,7 @@ const report = (days: number) => ({
     matches: emptyMatches,
     points: [],
     maps: [],
-    servers: [],
+    sampledServerCount: 0,
     scope: { game: null, map: null, timeZone: 'UTC' },
     scopeOptions: { games: [], maps: [] },
     registeredServerCount: 0,
@@ -71,6 +71,26 @@ function setup(fetcher: typeof fetch) {
 }
 
 describe('metrics background refresh', () => {
+    it.each([undefined, null, -1, 1.5, '1'])(
+        'rejects an invalid sampled-server count (%s) and accepts a count without server rows',
+        async (sampledServerCount) => {
+            const value = { ...report(7), sampledServerCount: 2 };
+            const refresh = setup(
+                vi
+                    .fn()
+                    .mockResolvedValueOnce(Response.json({ ...value, sampledServerCount }))
+                    .mockResolvedValueOnce(Response.json(value))
+            );
+            await refresh.refresh();
+            expect(refresh.onData).not.toHaveBeenCalled();
+            expect(refresh.onError).toHaveBeenLastCalledWith(
+                'The metrics response was incomplete.'
+            );
+            await refresh.refresh();
+            expect(refresh.onData).toHaveBeenLastCalledWith(value);
+        }
+    );
+
     it('keeps the previous report after failure and accepts a successful retry', async () => {
         const fetcher = vi
             .fn()

tests/unit/metrics.test.ts

@@ -79,7 +79,7 @@ describe('historical metrics', () => {
             expect(result.maps[0].matches).toEqual(result.matches);
             expect(result.maps[0].running).toEqual({ average: null, peak: 0, capturedHours: 0 });
             expect(result.registeredServerCount).toBe(0);
-            expect(result.servers).toEqual([]);
+            expect(result.sampledServerCount).toBe(0);
             expect(result.scopeOptions.maps).not.toContainEqual({ game: 't5', map: 'Future Map' });
         }
     );
@@ -304,7 +304,11 @@ describe('historical metrics', () => {
         const at = Date.UTC(2026, 0, 2);
         const sample = { server: 'removed', game: 't6', map: 'Town', players: 1, capacity: null };
         recordMetrics([sample], at);
-        expect(readMetrics(1, at + 30_000).servers[0].server).toBe('removed');
+        expect(readMetrics(1, at + 30_000)).toMatchObject({
+            sampledServerCount: 1,
+            registeredServerCount: 0,
+            maps: [{ game: 't6', map: 'Town', active: 30 / 3600 }]
+        });
         recordMetrics([sample], at + 32 * 86400_000);
         expect(db().prepare('SELECT COUNT(*) AS n FROM metric_samples').get()).toEqual({ n: 1 });
     });
@@ -318,7 +322,7 @@ describe('historical metrics', () => {
             firstRetainedSampleAt: null,
             latestSampleAt: null,
             registeredServerCount: 0,
-            servers: [],
+            sampledServerCount: 0,
             maps: []
         });
         db().prepare('INSERT INTO servers (name, destroyed_at) VALUES (?, ?)').run('current', null);
@@ -332,7 +336,7 @@ describe('historical metrics', () => {
             firstRetainedSampleAt: at,
             latestSampleAt: at,
             registeredServerCount: 1,
-            servers: [],
+            sampledServerCount: 0,
             maps: [],
             summary: { observed: 0, unknown: 0 }
         });
@@ -351,7 +355,7 @@ describe('historical metrics', () => {
         );
         const initial = readMetrics(1, at);
         expect(initial.latestSampleAt).toBe(at);
-        expect(initial.servers).toHaveLength(1);
+        expect(initial.sampledServerCount).toBe(1);
         expect(initial.summary).toEqual({
             observed: 0,
             active: 0,
@@ -404,9 +408,7 @@ describe('historical metrics', () => {
         expect(result.summary.active * 3600).toBeCloseTo(90);
         expect(result.summary.idle * 3600).toBeCloseTo(90);
         expect(result.summary.playerHours * 3600).toBeCloseTo(300);
-        expect(
-            result.servers.find((server) => server.server === 'two')!.observed * 3600
-        ).toBeCloseTo(30);
+        expect(result.sampledServerCount).toBe(2);
         const town = result.maps.find((map) => map.game === 't6' && map.map === 'Town')!;
         expect(town.observed * 3600).toBeCloseTo(60);
         expect(town.availabilityObserved * 3600).toBeCloseTo(30);
@@ -418,9 +420,6 @@ describe('historical metrics', () => {
             expect(result.points.reduce((sum, point) => sum + point[field], 0)).toBeCloseTo(
                 result.summary[field]
             );
-            expect(result.servers.reduce((sum, server) => sum + server[field], 0)).toBeCloseTo(
-                result.summary[field]
-            );
             expect(result.maps.reduce((sum, map) => sum + map[field], 0)).toBeCloseTo(
                 result.summary[field]
             );
@@ -436,6 +435,7 @@ describe('historical metrics', () => {
         recordMetrics([{ ...sample, players: 4 }], at + 60_000);
         const result = readMetrics(1, at + 30_000);
         expect(result.latestSampleAt).toBe(at);
+        expect(result.sampledServerCount).toBe(1);
         expect(result.summary.playerHours * 3600).toBeCloseTo(30);
     });
 
@@ -520,7 +520,7 @@ describe('historical metrics', () => {
         expect(result.summary.playerHours * 3600).toBeCloseTo(60);
         expect(result.previous.summary.active * 3600).toBeCloseTo(30);
         expect(result.previous.summary.playerHours * 3600).toBeCloseTo(120);
-        expect(result.servers.map((server) => server.server)).toEqual(['one']);
+        expect(result.sampledServerCount).toBe(1);
         expect(result.maps.map((map) => [map.game, map.map])).toEqual([['t5', 'Moon']]);
         expect(result.scopeOptions).toEqual({
             games: ['t5', 't6'],
@@ -557,7 +557,7 @@ describe('historical metrics', () => {
             scopeLatestSampleAt: null,
             summary: { observed: 0, unknown: 0 },
             maps: [],
-            servers: [],
+            sampledServerCount: 0,
             pooledAvailability: { value: null },
             running: { average: null, peak: 0, capturedHours: 0 },
             previous: { firstSampleAt: null, lastSampleAt: null, partialHistory: true }
@@ -598,6 +598,7 @@ describe('historical metrics', () => {
         recordMetrics([one, two], now - 30_000);
         const result = readMetrics(1, now);
         expect(result.running.average).toBeCloseTo(1.6);
+        expect(result.sampledServerCount).toBe(3);
         expect(result.running.peak).toBe(3);
         expect(result.running.capturedHours * 3600).toBeCloseTo(150);
         expect(result.maps[0].running).toEqual(result.running);
@@ -939,7 +940,7 @@ describe('historical metrics', () => {
         expect(result.heatmap.cells.filter((cell) => cell.observed > 0)).toHaveLength(1);
     });
 
-    it('counts unknown heatmap evidence and distinguishes retained names from current registrations', async () => {
+    it('counts unknown heatmap evidence and sampled names independently of current registrations', async () => {
         const { recordMetrics, readMetrics } =
             await import('../../src/lib/server/fleet/metrics.js');
         const { db } = await import('../../src/lib/server/db/index.js');
@@ -949,8 +950,7 @@ describe('historical metrics', () => {
             [sample, { ...sample, server: 'removed' }, { ...sample, server: 'tombstone' }],
             at
         );
-        // A newly registered name can link to the current server without asserting
-        // that its earlier historical observations belong to this registration.
+        // Current registration counts stay separate from sampled names, including reuse.
         db()
             .prepare('INSERT INTO servers (name, created_at) VALUES (?, ?)')
             .run('reused', new Date(at + 15_000).toISOString());
@@ -958,14 +958,9 @@ describe('historical metrics', () => {
             .prepare('INSERT INTO servers (name, destroyed_at) VALUES (?, ?)')
             .run('tombstone', new Date(at).toISOString());
         const result = readMetrics(1, at + 30_000);
-        expect(result.servers.find((server) => server.server === 'reused')!.currentRegistered).toBe(
-            true
-        );
-        expect(
-            result.servers
-                .filter((server) => server.server !== 'reused')
-                .every((server) => !server.currentRegistered)
-        ).toBe(true);
+        expect(result.sampledServerCount).toBe(3);
+        expect(result.registeredServerCount).toBe(1);
+        expect(result).not.toHaveProperty('servers');
         expect(
             result.heatmap.cells.reduce((sum, cell) => sum + cell.unknown, 0) * 3600
         ).toBeCloseTo(90);

tests/unit/ui-metrics-page.test.ts

@@ -1,11 +1,6 @@
 import { beforeEach, expect, it, vi } from 'vitest';
 import { render } from 'svelte/server';
-import type {
-    MetricsData,
-    MapMetrics,
-    ServerMetrics,
-    MatchMetrics
-} from '../../src/lib/metrics.js';
+import type { MetricsData, MapMetrics, MatchMetrics } from '../../src/lib/metrics.js';
 import MetricsPage from '../../src/routes/metrics/+page.svelte';
 import MetricsSummary from '../../src/lib/ui/components/metrics/MetricsSummary.svelte';
 import MetricsTables from '../../src/lib/ui/components/metrics/MetricsTables.svelte';
@@ -53,15 +48,6 @@ const map = (i: number, changes: Partial<MapMetrics> = {}): MapMetrics => ({
     policy: null,
     ...changes
 });
-const server = (i: number): ServerMetrics => ({
-    server: `t5_zombie_theater_${i}`,
-    currentRegistered: i !== 1,
-    observed: 10,
-    active: i / 10,
-    idle: 10 - i / 10,
-    unknown: 0,
-    playerHours: i
-});
 function report(): MetricsData {
     const now = Date.parse('2026-10-06T12:00:00Z');
     const summary = { observed: 10, active: 5, idle: 5, unknown: 2, playerHours: 20 };
@@ -81,7 +67,7 @@ function report(): MetricsData {
         summary,
         running: { average: 12, peak: 24, capturedHours: 1 },
         maps: Array.from({ length: 24 }, (_, i) => map(i + 1)),
-        servers: Array.from({ length: 24 }, (_, i) => server(i + 1)),
+        sampledServerCount: 24,
         points: [
             {
                 ...summary,
@@ -120,6 +106,28 @@ function scope(search: string, stateSearch?: string) {
 }
 beforeEach(() => scope(''));
 
+it.each([
+    [0, 'No captured time in this scope'],
+    [1, 'Waiting for observed time']
+] as const)('uses the sampled-server count %i for the empty state', (sampledServerCount, title) => {
+    const data = report();
+    data.summary = { observed: 0, active: 0, idle: 0, unknown: 0, playerHours: 0 };
+    data.running = { average: null, peak: 0, capturedHours: 0 };
+    data.matches = matches({
+        started: 0,
+        withRecordedPlayers: 0,
+        averageGroupSize: null,
+        solo: 0,
+        soloShare: null
+    });
+    data.maps = [];
+    data.sampledServerCount = sampledServerCount;
+    const body = render(MetricsPage, {
+        props: { data: { ...data, user: null, setupRequired: false } }
+    }).body;
+    expect(body).toContain(title);
+});
+
 it('shows a summary and one paginated breakdown, preserving scope on range links', () => {
     scope('?game=t5&days=7&view=maps&mapPage=2');
     const body = render(MetricsPage, {
@@ -271,7 +279,7 @@ it('keeps match summaries and map rows visible without any retained occupancy sa
     data.firstRetainedSampleAt = null;
     data.scopeFirstSampleAt = null;
     data.scopeLatestSampleAt = null;
-    data.servers = [];
+    data.sampledServerCount = 0;
     data.maps = [
         map(1, {
             ...data.summary,