92 lines
2.6 KiB
TypeScript
92 lines
2.6 KiB
TypeScript
 
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// Cross-process single-writer lease for a complete Obelisk index build. The
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// lock lives in a dedicated SQLite database so node:sqlite and better-sqlite3
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// share identical locking semantics on every supported platform.
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import { mkdirSync } from 'node:fs';
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import { dirname, join } from 'node:path';
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export interface WriterLeaseDb {
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exec(sql: string): unknown;
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close(): void;
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}
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export interface WriterLease {
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release(): void;
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}
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export interface AcquireWriterLeaseOptions {
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lockPath: string;
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openDb: (path: string) => WriterLeaseDb;
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waitMs?: number;
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retryDelayMs?: number;
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now?: () => number;
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sleep?: (ms: number) => void;
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}
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const BUSY_MESSAGE = /SQLITE_BUSY|database is locked|database is busy/i;
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function isBusy(error: unknown): boolean {
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const raw = error as { code?: unknown; errcode?: unknown; message?: unknown } | null;
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const code = raw?.code ?? raw?.errcode;
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return (
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(typeof code === 'string' && code.startsWith('SQLITE_BUSY')) ||
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(typeof raw?.message === 'string' && BUSY_MESSAGE.test(raw.message))
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);
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}
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function syncSleep(ms: number): void {
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if (ms <= 0) return;
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try {
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Atomics.wait(new Int32Array(new SharedArrayBuffer(4)), 0, 0, ms);
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} catch {
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// If synchronous sleeping is unavailable, the bounded attempt count below
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// still prevents an infinite acquisition loop.
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}
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}
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export function writerLockPathFor(dbPath: string): string {
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return join(dirname(dbPath), 'writer.lock.sqlite');
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}
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export function acquireWriterLease({
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lockPath,
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openDb,
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waitMs = 0,
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retryDelayMs = 25,
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now = Date.now,
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sleep = syncSleep,
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}: AcquireWriterLeaseOptions): WriterLease | null {
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mkdirSync(dirname(lockPath), { recursive: true });
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const startedAt = now();
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const maxAttempts = waitMs > 0 ? Math.ceil(waitMs / Math.max(1, retryDelayMs)) + 1 : 1;
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for (let attempt = 0; attempt < maxAttempts; attempt += 1) {
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const db = openDb(lockPath);
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try {
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db.exec('PRAGMA busy_timeout=0');
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db.exec('BEGIN IMMEDIATE');
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let released = false;
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return {
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release() {
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if (released) return;
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released = true;
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try {
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db.exec('ROLLBACK');
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} catch {
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// Closing the connection releases any remaining SQLite lock.
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} finally {
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db.close();
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}
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},
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};
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} catch (error) {
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db.close();
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if (!isBusy(error)) throw error;
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const remaining = waitMs - (now() - startedAt);
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if (remaining <= 0 || attempt + 1 >= maxAttempts) return null;
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sleep(Math.min(retryDelayMs, remaining));
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}
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}
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return null;
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}
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