Function tryAcquireEventsLock

cli/src/events/lock.ts:18–59

(cacheDir: string)

 * Call `releaseEventsLock` to release the lock at the end of the process.
 */
export async function tryAcquireEventsLock(cacheDir: string): Promise<boolean> {
    const lockPath = eventsLockPath(cacheDir);
    await fs.mkdir(cacheDir, { recursive: true });

    try {
        const raw = await fs.readFile(lockPath, 'utf8');
        const parsed = JSON.parse(raw) as unknown;
        const holderPid =
            typeof parsed === 'object' &&
            parsed !== null &&
            typeof (parsed as { pid?: unknown }).pid === 'number'
                ? (parsed as { pid: number }).pid
                : NaN;

        if (Number.isInteger(holderPid) && holderPid > 0 && isProcessAlive(holderPid)) {
            return false;
        }
        await fs.unlink(lockPath).catch(() => {});
    } catch (error: unknown) {
        const err = error as NodeJS.ErrnoException;
        // ENOENT = no such file or directory
        if (err.code !== 'ENOENT') {
            throw error;
        }
    }

    const payload: EventsLockPayload = { pid: process.pid };
    try {
        await fs.writeFile(lockPath, JSON.stringify(payload), {
            flag: 'wx', // Fail if file already exists.
            encoding: 'utf8',
        });
    } catch (error: unknown) {
        const err = error as NodeJS.ErrnoException;
        // EEXIST = file already exists
        if (err.code === 'EEXIST') {
            return false;
        }
        throw error;
    }
    return true;
}

function eventsLockPath(cacheDir: string): string {
    return path.join(cacheDir, EVENTS_LOCK_FILE);