Managing concurrency and ensuring that multiple threads can safety share resources is a perennial challenge in software development. In JavaScript, this issue comes in the form of race conditions where two or more scripts try to manipulate the same data or resource at the same time. With the introduction of the Web Locks API, developers are provided a method for coordinating these resource accesses safely, avoiding conflicts and ensuring reliable applications while still maintaining smooth UX.
Understanding Race Conditions
Before diving into the Web Locks API, it's important to understand what race conditions are. A race condition occurs when the outcome of a process, operation, or software sequence depends on the sequence or timing of uncontrollable events, such as processor scheduling and multi-thread execution.
Introduction to the Web Locks API
The Web Locks API allows you to asynchronously acquire locks in the browser, which coordinate energy-intensive tasks and prevent concurrent execution conflicts. Unlike traditional locking mechanisms which can block an entire process, the Web Locks API uses non-blocking API calls, which improve user experience by letting the browser remain responsive.
Let's see how this API works using practical examples:
Basic Lock Acquisition
The Web Locks API provides navigator.locks to acquire locks. Here's a simple example of acquiring and releasing a lock:
navigator.locks.request('resource-name', async lock => {
console.log('Lock acquired!');
// Perform operations safely here
await doSomeImportantTask();
// Once the control leaves this callback, the lock is automatically released
console.log('Lock released!');
});Handling Lock Contention
If your lock request is delayed due to another lock being held, the Web Locks API provides queue-based lock management. Consider this extended example:
const lockOptions = {mode: 'exclusive'};
navigator.locks.request('resource-name', lockOptions, async lock => {
console.log('Exclusive lock acquired!');
await someExclusiveTask();
console.log('Exclusive task completed!');
});The option {mode: 'exclusive'} indicates that this task needs exclusive access. The default mode is exclusive, so specifying it is usually just for clarity.
Managing Multiple Locks
You may often need to manage multiple resources in a synchronized way. Here's how you can chain together lock requests:
async function handleMultipleLocks() {
await navigator.locks.request('lock-a', async () => {
console.log('Lock A acquired');
await navigator.locks.request('lock-b', async () => {
console.log('Lock B acquired');
await doCombinedOperation();
console.log('Operations with both locks completed');
});
});
}
handleMultipleLocks();Imminence of Locks
The Web Locks API also provides an 'if available' feature, helping you acquire a lock only if it's immediately available, thereby avoiding waiting.
navigator.locks.request('prioritary-resource', {ifAvailable: true}, lock => {
if (lock) {
console.log('Lock acquired immediately!');
importantNonBlockingTask();
} else {
console.log('Lock not available, skipping task');
}
});Best Uses and Considerations
While the Web Locks API is powerful, it’s essential to keep certain practices in mind:
- Use locks to coordinate resource heavy operations, particularly read and write conflicts on storage.
- Limit lock scope as narrowly as possible to prevent tying up resources longer than necessary.
- Consider potential wait times block other operations, opting for timeouts or
{ifAvailable: true}modes where non-critical processes are involved.
Overall, the Web Locks API empowers you to write cleaner and safer concurrency in your web applications, fostering smoother interactions and more reliable functionalities.
