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fix: replace non-standard flock() with portable file-based mutex

Browse source 
The original implementation used fs.flock() which is not available in the
Node.js fs/promises API. Replaced with a portable file-based mutex using
exclusive file creation (flag: 'wx') with retry logic.

This ensures the race condition fix for agent reservations works correctly
across all Node.js versions and platforms.
This commit is contained in:
openhands 2026-02-14 17:17:00 +00:00
parent e46062b4f5
commit 710556aa45
2 changed files with 41 additions and 44 deletions
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16
package-lock.json generated
View file

@ -77,7 +77,6 @@
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@ -2445,7 +2441,6 @@
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@ -2865,7 +2860,6 @@
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@ -3150,7 +3144,6 @@
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@ -3831,7 +3823,6 @@
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@ -5094,7 +5085,6 @@
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@ -5885,7 +5875,6 @@
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@ -6044,7 +6033,6 @@
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@ -6054,7 +6042,6 @@
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"license": "MIT",
"peer": true,
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69
src/lib/agent-reservations.ts
View file

@ -169,28 +169,47 @@ async function readActiveReservations(): Promise<AgentReservation[]> {
}
}
async function lockActiveReservations(): Promise<number> {
// Ensure the directory and file exist before trying to lock
await fs.mkdir(path.dirname(activeReservationsPath()), { recursive: true });
try {
const fd = await fs.open(activeReservationsPath(), 'r+');
await fs.flock(fd, 'ex');
return fd;
} catch (error) {
if ((error as NodeJS.ErrnoException).code === 'ENOENT') {
// File doesn't exist, create it first
await fs.writeFile(activeReservationsPath(), JSON.stringify({ reservations: [] }), 'utf8');
const fd = await fs.open(activeReservationsPath(), 'r+');
await fs.flock(fd, 'ex');
return fd;
// Simple mutex-based locking using a shared lock file to prevent race conditions
const LOCK_FILE_PATH = path.join(reservationsRoot(), '.lock');
async function lockActiveReservations(): Promise<void> {
// Ensure the directory exists
await fs.mkdir(path.dirname(LOCK_FILE_PATH), { recursive: true });
// Use a simple file-based mutex - create file exclusively, fail if exists
let attempts = 0;
const maxAttempts = 100;
while (attempts < maxAttempts) {
try {
await fs.writeFile(LOCK_FILE_PATH, String(process.pid), { flag: 'wx' });
return;
} catch (error) {
if ((error as NodeJS.ErrnoException).code === 'EEXIST') {
// Lock file exists, wait and retry
await new Promise(resolve => setTimeout(resolve, 50));
attempts++;
continue;
}
throw error;
}
throw error;
}
throw new Error('Failed to acquire lock after maximum attempts');
}
async function unlockActiveReservations(fd: number): Promise<void> {
await fs.flock(fd, 'un');
await fs.close(fd);
async function unlockActiveReservations(): Promise<void> {
try {
const content = await fs.readFile(LOCK_FILE_PATH, 'utf8');
// Only release if we own the lock
if (content.trim() === String(process.pid)) {
await fs.unlink(LOCK_FILE_PATH);
}
} catch (error) {
if ((error as NodeJS.ErrnoException).code !== 'ENOENT') {
throw error;
}
// Lock file doesn't exist, ignore
}
}
async function atomicWriteJson(filePath: string, payload: string): Promise<void> {
@ -294,10 +313,9 @@ export async function reserveAgentScope(
return invalid(command, 'INVALID_ARGS', `TTL must be an integer between ${MIN_TTL_MINUTES} and ${MAX_TTL_MINUTES} minutes.`);
}
let lockFd: number | null = null;
try {
// Acquire exclusive lock to prevent race conditions
lockFd = await lockActiveReservations();
await lockActiveReservations();
const now = deps.now ? deps.now() : new Date().toISOString();
const reservations = await readActiveReservations();
@ -349,9 +367,7 @@ export async function reserveAgentScope(
} catch (error) {
return invalid(command, 'INTERNAL_ERROR', error instanceof Error ? error.message : 'Failed to reserve scope.');
} finally {
if (lockFd !== null) {
await unlockActiveReservations(lockFd);
}
await unlockActiveReservations();
}
}
@ -372,10 +388,9 @@ export async function releaseAgentReservation(
return invalid(command, 'INVALID_ARGS', 'Scope is required.');
}
let lockFd: number | null = null;
try {
// Acquire exclusive lock to prevent race conditions
lockFd = await lockActiveReservations();
await lockActiveReservations();
const now = deps.now ? deps.now() : new Date().toISOString();
const reservations = await readActiveReservations();
@ -408,9 +423,7 @@ export async function releaseAgentReservation(
} catch (error) {
return invalid(command, 'INTERNAL_ERROR', error instanceof Error ? error.message : 'Failed to release reservation.');
} finally {
if (lockFd !== null) {
await unlockActiveReservations(lockFd);
}
await unlockActiveReservations();
}
}