queuing
v1.3.0
Published
que tasks
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/ / \ \| | \_/ __ \| | \ |/ \ / ___\
/ \_/. \ | /\ ___/| | / | | \/ /_/ >
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A Forked module from queue with ES6 Syntax, and a retry
feature
Asynchronous function queue with adjustable concurrency.
This module exports a class Queuing
that implements most of the Array
API. Pass async functions (ones that accept a callback or return a promise) to an instance's additive array methods. Processing begins when you call q.start()
.
Install
npm install queuing
Test
npm test
API
var q = queuing([opts])
Constructor. opts
may contain inital values for:
q.concurrency
q.timeout
q.autostart
q.results
q.retry
q.delay
Instance methods
q.start([cb])
cb, if passed, will be called when the queue empties or when an error occurs.
q.stop()
Stops the queue. can be resumed with q.start()
.
q.end([err])
Stop and empty the queue immediately.
Instance methods mixed in from Array
Mozilla has docs on how these methods work here.
q.push(element1, ..., elementN)
q.unshift(element1, ..., elementN)
Properties
q.concurrency
Max number of jobs the queue should process concurrently, defaults to Infinity
.
q.timeout
Milliseconds to wait for a job to execute its callback.
q.autostart
Ensures the queue is always running if jobs are available. Useful in situations where you are using a queue only for concurrency control.
q.results
An array to set job callback arguments on.
q.retry
Put back the job in que upon error.
q.delay
Milliseconds to wait before job execution per session
q.length
Jobs pending + jobs to process (readonly).
Events
q.emit('success', result, job)
After a job executes its callback.
q.emit('error', err, job)
After a job passes an error to its callback.
q.emit('retry', err, job)
After a job passes an error and queued back to jobs list
q.emit('timeout', continue, job)
After q.timeout
milliseconds have elapsed and a job has not executed its callback.
q.emit('end'[, err])
After all jobs have been processed
Example
var queue = require('queuing')
var q = queue()
var results = []
// add jobs using the familiar Array API
q.push(function (cb) {
results.push('two')
cb()
})
q.push(
function (cb) {
results.push('four')
cb()
},
function (cb) {
results.push('five')
cb()
}
)
// jobs can accept a callback or return a promise
q.push(function () {
return new Promise(function (resolve, reject) {
results.push('one')
resolve()
})
})
q.unshift(function (cb) {
results.push('one')
cb()
})
// use the timeout feature to deal with jobs that
// take too long or forget to execute a callback
q.timeout = 100
q.on('timeout', function (next, job) {
console.log('job timed out:', job.toString().replace(/\n/g, ''))
next()
})
q.push(function (cb) {
setTimeout(function () {
console.log('slow job finished')
cb()
}, 200)
})
q.push(function (cb) {
console.log('forgot to execute callback')
})
// get notified when jobs complete
q.on('success', function (result, job) {
console.log('job finished processing:', job.toString().replace(/\n/g, ''))
})
// begin processing, get notified on end / failure
q.start(function (err) {
if (err) throw err
console.log('all done:', results)
})
Releases
The latest stable release is published to npm.
- Initial fork
- New
reque
option
- Removal of non-useful Array methods
- Refactor test
- Rename
reque
option toretry
option - Add
delay
option - Emitter will only emit
end
event if the job que is empty on process.nextTick's event, approx 4-5 millisecond - Wrap all jobs inside a promise
- Update modules
- Extend nodejs compatibilty to Nodejs 12
- Use Travis
Releases from original module
The latest stable release is published to npm. Abbreviated changelog below:
- 4.4
- Add results feature
- 4.3
- Add promise support (@kwolfy)
- 4.2
- Unref timers on end
- 4.1
- Add autostart feature
- 4.0
- Change license to MIT
- 3.1.x
- Add .npmignore
- 3.0.x
- Change the default concurrency to
Infinity
- Allow
q.start()
to accept an optional callback executed onq.emit('end')
- Change the default concurrency to
- 2.x
- Major api changes / not backwards compatible with 1.x
- 1.x
- Early prototype
License
Copyright © 2014 Jesse Tane [email protected] Copyright © 2018 Uni Sayo [email protected]
This work is free. You can redistribute it and/or modify it under the terms of the MIT License. See LICENSE for full details.