Lock on asynchronous code
- ES6 promise supported
- Multiple keys lock supported
- Timeout supported
- Pending task limit supported
- Domain reentrant supported
- 100% code coverage
I did not create this package, and I will not add any features to it myself. I was granted the ownership because it was no longer being maintained, and I volunteered to fix a bug.
If you have a new feature you would like to have incorporated, please send me a PR and I will be happy to work with you and get it merged. For any bugs, PRs are most welcome but when possible I will try to get them resolved as soon as possible.
Why do you need locking on single threaded nodejs?
Nodejs is single threaded, and the code execution never gets interrupted inside an event loop, so locking is unnecessary? This is true ONLY IF your critical section can be executed inside a single event loop. However, if you have any async code inside your critical section (it can be simply triggered by any I/O operation, or timer), your critical logic will across multiple event loops, therefore it's not concurrency safe!
Consider the following code
The above code simply multiply a redis key by 2. However, if two users run concurrency, the execution order may like this
user1: redis.get('key') -> 1 user2: redis.get('key') -> 1 user1: redis.set('key', 1 x 2) -> 2 user2: redis.set('key', 1 x 2) -> 2
Obviously it's not what you expected
With asyncLock, you can easily write your async critical section
var AsyncLock = ;var lock = ;/*** @param* @param* @param* @param*/lock;// Promise modelock;
// Callback modelock;// Promise modelock;
Acquire multiple keys
Domain reentrant lock
Lock is reentrant in the same domain
var domain = ;var lock = domainReentrant : true;var d = domain;d;
// Specify timeoutvar lock = timeout: 5000;lock;// Set max pending tasksvar lock = maxPending: 1000;lock// Whether there is any running or pending async functionlock;// Use your own promise library instead of the global Promise variablevar lock = Promise: ; // Bluebirdvar lock = Promise: ; // Q// Add a task to the front of the queue waiting for a given locklock; // runs immediatelylock; // added to queuelock; // jumps queue and runs before fn2
See issue tracker.
MIT, see LICENSE