egg-schedule

A schedule plugin for egg. It supports two scheduler types, worker and all, and can be extended by other plugins.

Installation

$ npm i egg-schedule --save

Usage

egg-schedule is a plugin that has been built-in for egg. It is enabled by default.

// {app_root}/config/plugin.js
exports.schedule = {
  package: 'egg-schedule'
};
 
// {app_root}/app/schedule/cleandb.js
/**
* @property {Object} schedule
*  - {String} type - schedule type, `worker` or `all`
*  - {String} [cron] - cron expression, [see below](#cron-style-scheduling)
*  - {String | Number} [interval] - interval expression in millisecond or express explicitly like '1h'. [see below](#interval-style-scheduling)
*  - {Boolean} [immediate] - To run a scheduler at startup
*  - {Boolean} [disable] - whether to disable a scheduler, usually use in dynamic schedule
*/
exports.schedule = {
  type: 'worker',
  cron: '0 0 3 * * *',
  // interval: '1h',
  // immediate: true,
};
 
exports.task = function* (ctx) {
  yield ctx.service.db.cleandb();
};

Overview

egg-schedule supports both time-based scheduling and interval-based scheduling.

Schedule decision is being made by agent process. agent triggers a task and sends message to worker process. Then, one or all worker process(es) execute the task based on schedule type.

To setup a schedule task, simply create a job file in {app_root}/app/schedule. A file contains one job and export schedule and task properties.

The rule of thumbs is one job per file.

Task

Task is a generator function, and accept one parameter, ctx. The syntax is, exports.task = function* (ctx) { ... };

When the scheduled task runs, the scheduled job information will be logged and written to a local file in a folder called /logs. The log file contains many useful information, for example,

• ctx.method: SCHEDULE
• ctx.path: /__schedule/${schedulePath}. example path: /__schedule?path=/FULL_PATH_TO/cleandb.js&type=worker&interval=3h
• ctx.query: scheule config(type=worker&cron=*%2F5%20*%20*%20*%20*%20*)

To create a task, it is as simple as write a generator function. For example:

// A simple logger example
exports.task = function* (ctx) {
  ctx.logger.info('Info about your task');
};

// A real world example: wipe out your database.
// Use it with caution. :)
exports.task = function* (ctx) {
  yield ctx.service.db.cleandb();
};

Scheduling

schedule is an object that contains one required property, type, four optional properties, { cron, interval, immediate, disable }.

Cron-style Scheduling

Use cron-parser.

Note: cron-parser support second as optional that is not supported by linux crontab.

@hourly / @daily / @weekly / @monthly / @yearly is also supported.

*    *    *    *    *    *
┬    ┬    ┬    ┬    ┬    ┬
│    │    │    │    │    |
│    │    │    │    │    └ day of week (0 - 7) (0 or 7 is Sun)
│    │    │    │    └───── month (1 - 12)
│    │    │    └────────── day of month (1 - 31)
│    │    └─────────────── hour (0 - 23)
│    └──────────────────── minute (0 - 59)
└───────────────────────── second (0 - 59, optional)

Example:

// To execute task every 3 hours
exports.schedule = {
  type: 'worker',
  cron: '0 0 */3 * * *'
};

Interval-style Scheduling

To use setInterval, and support ms conversion style

Example:

// To execute task every 3 hours
exports.schedule = {
  type: 'worker',
  interval: '3h'
};

Schedule Type

Build-in support is:

• worker: will be executed in one random worker when schedule run.
• all: will be executed in all workers when schedule run.

Custom schedule

To create a custom schedule, simply create a schedule with a type custom and its corresponding method. Inside your custom method, you can schedule the task to be executed by one random worker or all workers with the built-in method sender.one() or sender.all().

// {app_root}/agent.js
const SCHEDULE_HANDLER = Symbol.for('egg#scheduleHandler');
 
module.exports = agent => {
  // sender.one() - will notify one random worker to execute task
  // sender.all() - will notify all workers
  agent[SCHEDULE_HANDLER].custom = (schedule, sender) =>
    setInterval(sender.one, schedule.interval);
};
 
// {app_root}/app/schedule/other.js
exports.schedule = {
  type: 'custom'
};

Dynamic schedule

// {app_root}/app/schedule/sync.js
module.exports = app => {
  exports.schedule = {
    interval: 10000,
    type: 'worker',
    // only start task when hostname match
    disable: require('os').hostname() !== app.config.sync.hostname
  };
 
  exports.task = function* (ctx) {
    yield ctx.sync();
  };
 
  return exports;
};

Testing

app.runSchedule(scheduleName) is provided by egg-schedule plugin only for test purpose.

Example:

it('test a schedule task', function* () {
  // get app instance
  yield app.runSchedule('clean_cache');
});

Questions & Suggestions

Please open an issue here.

License

MIT