What happens if a resource is already locked?

Question

I'm trying to use RedLock to prevent 2 users from doing an operation on the same resource at once (Booking something too quickly from one another). But I want it to fail completely if the resource is already acquired by someone else (Booking availability will be gone after the transaction of request commits). It's not clear to me on docs what happens if the resource is still locked and how to fail at that point. Does it just throw an error? https://github.com/mike-marcacci/node-redlock#usage-promise-style.

const redlock = new Redlock(...);
let lock;
try {
  lock = redlock.lock('bookId', 120000);
} catch (err) {
  // ... lock failed to be acquired because someone else still had it? (after retries are finish)
}

Answer 1

The above example I used did in fact work. Once all tries to acquire the lock are spent, it does throw an error. In most mutual exclusion cases, that shouldn't occur. It should be configured such that there is enough time for other clients waiting on the locked resource to eventually get it. In the case you want it to fail completely (You don't want the second client to ever acquire the resource), just configure the Redlock for a single attempt and the Redlock will throw.

const redlock = new Redlock(...);
let lock;
try {
  lock = redlock.lock('bookId', 120000);
} catch (err) {
  // Attempted to grab lock but failed after all attempts (configured) are finished
}