typed-scheduler v0.3.1
typed-scheduler
A Scheduler written in TypeScript for concurrency-limiting and rate-limiting
Docs | GitHub | npm | Yarn
Table of Contents
Installing
npm
$ npm i --save typed-scheduler
Yarn
$ yarn add typed-scheduler
Importing
typed-scheduler
is pre-bundled using the UMD pattern to support the
following module formats.
ES Module
import Scheduler from 'typed-scheduler'
CommonJS
const Scheduler = require('typed-scheduler')
Browser Global
<script src="https://unpkg.com/typed-scheduler"></script>
AMD
define(['typed-scheduler'], function (Scheduler) {
})
Usage
Example
// rate limit to 2 messages every second
// defaults to 3 priorities
const scheduler = new Scheduler({ concurrency: 2, rate: 1000 })
// queue 120 messages synchronously
// scheduler will throttle to 2 messages per second
for (let i = 1; i <= 120; i++) {
// schedule with normal priority
scheduler.scheduleNormal(console.log, `message ${i}`)
}
priority
The second argument of schedule()
is used to set the priority class of the
scheduled function. The scheduler will handle scheduled functions in FIFO order
within each priority class, and higher priorities will always be handled before
lower priorities. A lower value means a higher priority.
ready()
and idle()
The output of this program demonstrates when each of these methods resolves.
import Scheduler from 'typed-scheduler'
function print (...args) {
console.log(`${(Date.now() / 1000).toFixed(3)}s`, ...args)
}
const scheduler = new Scheduler({ concurrency: 1, rate: 1000, priorities: 3 })
for (let i = 0; i < 3; i++) {
for (let j = 0; j < 3; j++) {
// interleave priority classes
scheduler.schedule(
() => print('task', i * 3 + j),
j
)
}
scheduler.ready(i).then(
() => print(`priority ${i} ready`)
)
}
scheduler.idle().then(
() => print('scheduler idle')
)
Output
0.079s task 0
1.103s task 3
2.109s task 6
2.109s priority 0 ready
3.113s task 1
4.119s task 4
5.119s task 7
5.119s priority 1 ready
6.123s task 2
7.123s task 5
8.129s task 8
8.129s priority 2 ready
9.135s scheduler idle
concurrency
and rate
Note that the following schedulers do not behave identically.
// 2 tasks every second
new Scheduler({ concurrency: 2, rate: 1000 })
// 1 task every half second
new Scheduler({ concurrency: 1, rate: 500 })
Using the options { concurrency: 2, rate: 1000 }
, the scheduler will execute
two tasks without delay, then wait a full second after either completes before
executing another task.
Using { concurrency: 1, rate: 500 }
will only execute one task at a time,
then wait for half a second after it completes before executing another task.
API
The complete reference API is available on GitHub Pages.
License
Copyright © 2019 Patrick Roberts
MIT License