Improve application responsiveness and background processing

src/lib/server/reports/index.ts

@@ -0,0 +1,64 @@
+import { Worker } from 'node:worker_threads';
+import { resolve } from 'node:path';
+import { config } from '../config.js';
+import { db } from '../db/index.js';
+import type { MetricsQuery, MetricsData } from '../../metrics.js';
+import type { LeaderboardOptions, LeaderboardResponse, PlayerProfile, LeaderboardEntry } from '../../leaderboard.js';
+
+class ReportWorker {
+    private worker: Worker | null = null;
+    private sequence = 0;
+    private pending = new Map<number, { resolve: (value: any) => void; reject: (error: Error) => void; timer: NodeJS.Timeout }>();
+    private flights = new Map<string, Promise<any>>();
+    async close() {
+        const worker = this.worker; this.worker = null;
+        for (const pending of this.pending.values()) { clearTimeout(pending.timer); pending.reject(new Error('Report service stopped')); }
+        this.pending.clear(); this.flights.clear();
+        await worker?.terminate();
+    }
+    run<T>(kind: string, input: unknown): Promise<T> {
+        const requestInput = input as { query?: MetricsQuery; now?: number };
+        const key = JSON.stringify(kind === 'metrics' ? [kind, requestInput.query, Math.floor(requestInput.now! / 30_000)] : [kind, input]);
+        const flight = this.flights.get(key);
+        if (flight) return flight;
+        if (this.pending.size >= 64) return Promise.reject(new Error('Reports are busy. Please retry shortly.'));
+        db(); // Finish migrations before opening the independent reader.
+        if (!this.worker) {
+            const worker = this.worker = new Worker(resolve(process.env.NODE_ENV === 'production' ? 'build/reports/worker.mjs' : '.svelte-kit/reports/worker.mjs'), { workerData: { dbPath: resolve(config.dbPath) } });
+            worker.on('message', ({ id, value, error, elapsedMs, cached }) => {
+                const pending = this.pending.get(id); if (!pending) return;
+                clearTimeout(pending.timer); this.pending.delete(id);
+                if (process.env.EC_PERF_LOG === 'true') console.info('[report]', { kind, elapsedMs, cached });
+                if (error) pending.reject(new Error(error)); else pending.resolve(value);
+                if (!this.pending.size) worker.unref();
+            });
+            const fail = (error: Error) => {
+                if (this.worker !== worker) return;
+                this.worker = null;
+                for (const pending of this.pending.values()) { clearTimeout(pending.timer); pending.reject(error); }
+                this.pending.clear(); void worker.terminate();
+            };
+            worker.on('error', fail);
+            worker.on('exit', () => fail(new Error('Report worker stopped. Please retry.')));
+        }
+        this.worker.ref();
+        const id = ++this.sequence;
+        const promise = new Promise<T>((resolve, reject) => {
+            const timer = setTimeout(() => {
+                // Reset the worker rather than leaving an expensive abandoned query queued.
+                const worker = this.worker; this.worker = null;
+                for (const item of this.pending.values()) { clearTimeout(item.timer); item.reject(new Error('Report timed out. Please retry.')); }
+                this.pending.clear(); void worker?.terminate();
+            }, 60_000);
+            this.pending.set(id, { resolve, reject, timer }); this.worker!.postMessage({ id, kind, input });
+        }).finally(() => { if (this.flights.get(key) === promise) this.flights.delete(key); });
+        this.flights.set(key, promise);
+        return promise;
+    }
+}
+const metrics = new ReportWorker();
+const leaderboard = new ReportWorker();
+export const metricsReport = (query: MetricsQuery) => metrics.run<MetricsData>('metrics', { query, now: Date.now() });
+export const leaderboardReport = (query: LeaderboardOptions) => leaderboard.run<LeaderboardResponse>('leaderboard', query);
+export const playerReport = (guid: string, offset: number, options: LeaderboardOptions) => leaderboard.run<{ profile: PlayerProfile | null; entry: LeaderboardEntry | null }>('player', { guid, offset, options });
+export async function closeReports() { await Promise.all([metrics.close(), leaderboard.close()]); }