|
|
- # run-queue
-
- A promise based, dynamic priority queue runner, with concurrency limiting.
-
- ```js
- const RunQueue = require('run-queue')
-
- const queue = new RunQueue({
- maxConcurrency: 1
- })
-
- queue.add(1, example, [-1])
- for (let ii = 0; ii < 5; ++ii) {
- queue.add(0, example, [ii])
- }
- const finished = []
- queue.run().then(
- console.log(finished)
- })
-
- function example (num, next) {
- setTimeout(() => {
- finished.push(num)
- next()
- }, 5 - Math.abs(num))
- }
- ```
-
- would output
-
- ```
- [ 0, 1, 2, 3, 4, -1 ]
- ```
-
- If you bump concurrency to `2`, then you get:
-
- ```
- [ 1, 0, 3, 2, 4, -1 ]
- ```
-
- The concurrency means that they don't finish in order, because some take
- longer than others. Each priority level must finish entirely before the
- next priority level is run. See
- [PRIORITIES](https://github.com/iarna/run-queue#priorities) below. This is
- even true if concurrency is set high enough that all of the regular queue
- can execute at once, for instance, with `maxConcurrency: 10`:
-
- ```
- [ 4, 3, 2, 1, 0, -1 ]
- ```
-
- ## API
-
- ### const queue = new RunQueue(options)
-
- Create a new queue. Options may contain:
-
- * maxConcurrency - (Default: `1`) The maximum number of jobs to execute at once.
- * Promise - (Default: global.Promise) The promise implementation to use.
-
- ### queue.add (prio, fn, args)
-
- Add a new job to the end of the queue at priority `prio` that will run `fn`
- with `args`. If `fn` is async then it should return a Promise.
-
- ### queue.run ()
-
- Start running the job queue. Returns a Promise that resolves when either
- all the jobs are complete or a job ends in error (throws or returns a
- rejected promise). If a job ended in error then this Promise will be rejected
- with that error and no further queue running will be done.
-
- ## PRIORITIES
-
- Priorities are any integer value >= 0.
-
- Lowest is executed first.
-
- Priorities essentially represent distinct job queues. All jobs in a queue
- must complete before the next highest priority job queue is executed.
-
- This means that if you have two queues, `0` and `1` then ALL jobs in `0`
- must complete before ANY execute in `1`. If you add new `0` level jobs
- while `1` level jobs are running then it will switch back processing the `0`
- queue and won't execute any more `1` jobs till all of the new `0` jobs
- complete.
|