@vwt12eh8/await-semaphore
v2.0.3
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Awaitable semaphore/mutex
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await-semaphore
Awaitable semaphore/mutex
A semaphore implementation using ES6 promises and supporting 3 styles:
- async/await style (needs typescript)
- thunk style (automatic acquire/release)
- promise style
Also includes Mutex
as a convenience for new Semaphore(1)
.
API
new Semaphore(count: number)
Create a new semaphore with the given count.
import {Semaphore} from 'await-semaphore';
var semaphore = new Semaphore(10);
semaphore.acquire(): Promise<() => void>
Acquire the semaphore and returns a promise for the release function. Be sure to handle release for exception case.
semaphore.acquire()
.then(release => {
//critical section...
doSomething()
.then(res => {
//...
release();
})
.catch(err => {
//...
release();
});
});
semaphore.use(thunk: () => Promise): Promise
Alternate method for using the semaphore by providing a thunk. This automatically handles acquire/release.
semaphore.use(() => {
//critical section...
});
new Mutex()
An alias for new Semaphore(1)
. Mutex has the same methods as Semaphore.
import {Mutex} from 'await-semaphore';
var mutex = new Mutex();
Examples
Create a version of fetch()
with concurrency limited to 10.
async/await style (typescript)
var semaphore = new Semaphore(10);
async function niceFetch(url) {
var release = await semaphore.acquire();
var result = await fetch(url);
release();
return result;
}
thunk style (javascript)
var semaphore = new Semaphore(10);
function niceFetch(url) {
return semaphore.use(() => fetch(url));
}
promise style (javascript)
var semaphore = new Semaphore(10);
function niceFetch(url) {
return semaphore.acquire()
.then(release => {
return fetch(url)
.then(result => {
release();
return result;
});
});
}