61 lines
1.6 KiB
JavaScript
61 lines
1.6 KiB
JavaScript
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// Simple PID-based lock file. Atomic via O_EXCL.
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// If a stale lock is found (PID no longer alive), it is removed.
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import { closeSync, openSync, readFileSync, unlinkSync, writeSync } from 'node:fs';
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function isAlive(pid) {
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try {
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process.kill(pid, 0);
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return true;
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} catch (e) {
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return e.code === 'EPERM';
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}
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}
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export function acquireLock(lockPath) {
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for (let attempt = 0; attempt < 2; attempt++) {
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try {
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const fd = openSync(lockPath, 'wx');
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writeSync(fd, String(process.pid));
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closeSync(fd);
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const release = () => {
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try {
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unlinkSync(lockPath);
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} catch {
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/* ignore */
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}
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};
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process.on('exit', release);
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process.on('SIGINT', () => {
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release();
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process.exit(130);
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});
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process.on('SIGTERM', () => {
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release();
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process.exit(143);
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});
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return release;
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} catch (err) {
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if (err.code !== 'EEXIST') throw err;
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// Lock exists — check if owner is still alive
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let pid = 0;
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try {
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pid = parseInt(readFileSync(lockPath, 'utf8').trim(), 10);
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} catch {
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/* unreadable */
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}
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if (pid && isAlive(pid)) {
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throw new Error(`Cron already running (PID ${pid}, lock ${lockPath})`);
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}
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// Stale lock — remove and retry
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console.log(`Removing stale lock (PID ${pid || '?'} no longer alive): ${lockPath}`);
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try {
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unlinkSync(lockPath);
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} catch {
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/* ignore */
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}
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}
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}
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throw new Error(`Could not acquire lock after retries: ${lockPath}`);
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}
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