README.md
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# mini-queue
Job queue
If you have different needs regarding the functionality, please add a [feature request](https://github.com/alykoshin/mini-queue/issues).
## Installation
```sh
npm install --save mini-queue
```
## Usage
```
QueueJob State Diagram (methods of JobQueue object)
======================
|
createJob |
+------V-----+
| new |
| |
+---+--+--+--+
| | | _rejectJob +------------+
| | +--------------------------------> reject |
| | | |
_startJob | | _queueJob +------------+
| +------------+
| |
| +-----v------+ _cancelJob
| | queue +-----------------+
| | | |
| +---+----^---+ |
| _dequeueJob | | |
| | | |
| | | _queueJob |
| +---v----+---+ +-V----------+
| | dequeue +---------------> cancel |
| | | _cancelJob | |
| +-----+------+ +------------+
| _startJob |
| |
| +----------+
| |
+---v----v---+ _terminateJob +------------+
| process +----------------------> terminate |
| | |(not implem)|
+-----+------+ +------------+
|
|
|
+-----v------+
| complete |
| |
+------------+
```
`job.journalEntry` for each state (`queue`, `dequeue`, `process`, `complete`, `reject`, `cancel`) stores the time when transition to state occured. If several changes has occured, only the last time is stored(`id` is job identifier `job.id`):
```json
{ id: 4,
new: 2017-11-10T08:37:17.428Z,
queue: 2017-11-10T08:37:17.428Z,
dequeue: 2017-11-10T08:37:17.941Z,
process: 2017-11-10T08:37:17.941Z,
complete: 2017-11-10T08:37:18.943Z },
```
For each `group` and `name` as provided in `option` for `createJob()`, `journalEntries` are kept ar array in `queue.journal` (newest is the first, oldest is the last).
Example (`group` and `name` not set, `default` value is used):
```json
journal: { group:
{ name:
[ { id: 5,
new: 2017-11-10T08:37:17.929Z,
reject: 2017-11-10T08:37:17.929Z },
. . .
{ id: 2,
new: 2017-11-10T08:37:16.426Z,
queue: 2017-11-10T08:37:16.427Z,
dequeue: 2017-11-10T08:37:16.937Z,
process: 2017-11-10T08:37:16.937Z,
complete: 2017-11-10T08:37:17.941Z } ] } } +2s
```
Up to `maxJournalLength` option for `createJob()` records are kept.
## Example
You may find this example in `demo` subdirectory of the package.
```js
"use strict";
process.env.DEBUG = 'queue,app';// + (process.env.DEBUG || '');
var util = require('util');
var debug = require('debug')('app');
//var Queue = require('express-queue');
var Queue = require('../');
var queue = new Queue({ activeLimit: 1, queuedLimit: 1, maxJournalLength: 4 });
// create jobs
var maxCount = 5,
count = 0;
var interval = setInterval(function() {
var jobData = {};
// Create new job for the queue
// If number of active job is less than `activeLimit`, the job will be started on Node's next tick.
// Otherwise it will be queued.
var job = queue.createJob(
jobData, // we may pass some data to job when calling queue.createJob() function
{ group: 'group', name: 'name' } // group/name to be used for journal
);
if (++count >= maxCount) {
clearInterval(interval);
setTimeout(()=> { // after last job has finished
debug('journal:', util.inspect(queue.journal, {depth:3}));
}, 1500);
}
}, 500);
// execute jobs
queue.on('process', function(job, jobDone) {
debug(`queue.on('process'): [${job.id}]: status: ${job.status}, journalEntry: ${JSON.stringify(job.journalEntry)}`);
// Here the job starts
//
// It is also possible to do the processing inside job.on('process'), just be careful
// to call jobDone() callback once and only once.
//
// Value of job.data is set to value passed to queue.createJob()
//
// Imitate job processing which takes 1 second to be finished
setTimeout(function() {
// Call the callback to signal to the queue that the job has finished
// and the next one may be started
jobDone();
// Now on Node's next tick the next job (if any) will be started
}, 1000);
});
// Signal about jobs rejected due to queueLimit
queue.on('reject', function(job) {
debug(`queue.on('reject'): [${job.id}]: status: ${job.status}, journalEntry: ${JSON.stringify(job.journalEntry)}`);
});
```
## Credits
[Alexander](https://github.com/alykoshin/)
# Links to package pages:
[github.com](https://github.com/alykoshin/mini-queue) [npmjs.com](https://www.npmjs.com/package/mini-queue) [travis-ci.org](https://travis-ci.org/alykoshin/mini-queue) [coveralls.io](https://coveralls.io/github/alykoshin/mini-queue) [inch-ci.org](https://inch-ci.org/github/alykoshin/mini-queue)
## License
MIT