cron-async

Javascript library for executing tasks on a schedule, using cron syntax, with async/await support. It is inspired by node-cron.

It's smart at handling async jobs. All executions are wrapped in a try-catch clause and errors are caught and logged. It also waits until the current iteration of a job has finished executing before starting the next iteration, regardless of the job's schedule.

Features:

• Works in both Node.js and Browsers.
• Performant: uses a single interval timer for all created jobs.
• Customizable logger.
• Typesript support / fully typed.
• Auto-generated API documentation.

Installation

• NPM: npm i cron-async
• Yarn: yarn add cron-async
• PNPM: pnpm add cron-async

Usage

First create a Cron instance:

import { Cron } from 'cron-async'

const cron = new Cron()
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Now add a job:

cron.createJob('job1', {
  cron: "*/1 * * * * *", // every second
  onTick: async () => {
    // do stuff in here on every iteration
  },
})
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The above job will run automatically every second. You can start and stop the job at any time:

cron.getJob('job1').stop() // stop the job

// ...

cron.getJob('job1').start() // resume the job
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You can also delete the job from the cron instance entirely in two ways:

// the following statements do the same thing...
cron.deleteJob('job1')
cron.getJob('job1').destroy()
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By defualt, the logger is the built-in console object. You can customize this by overriding the log config option:

cron.createJob('job1', {
  cron: "*/1 * * * * *", // every second
  onTick: async () => { /* do stuff */ },
  log: {
    trace: (msg) => { /* do something */ },
    debug: (msg) => { /* do something */ },
    error: (msg) => { /* do something */ },
  }
})
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You can also specify the job to NOT automatically run when created:

cron.createJob('job1', {
  cron: "*/1 * * * * *", // every second
  onTick: async () => { /* do stuff */ },
  dontAutoRun: true,
})

// later on, we can start the job
cron.getJob('job1').start()
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Each job keeps track of the number of iterations it has run:

cron.createJob('job1', {
  cron: "*/1 * * * * *", // every second
  onTick: async () => { /* do stuff */ },
  dontAutoRun: true,
})

// after some time....

const n = cron.getJob('job1').getNumIterations()

console.log( `Job has run ${n} times` )
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The onTick() function you provide is automatically wrapped in a try-catch clause by the scheduler. If you wish to process any thrown errors you can supply an onError handler:

cron.createJob('job1', {
  cron: "*/1 * * * * *", // every second
  onTick: async () => { /* do stuff */ },
  onError: (err: Error) => {
    // do something with the error
  }
})
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Finally, you can shutdown the Cron instance and its internal timer at any point using:

cron.shutdown()
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For other available methods and properties please see the API documentation.

Developer guide

To build both ESM and CommonJS output:

pnpm build
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To re-build the CommonJS output on chnage:

pnpm dev
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To test:

pnpm test
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To build the docs:

pnpm build-docs
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To publish a new release (this will create a tag, publish to NPM and publish the latest docs):

pnpm release
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License

Copyright (C) 2023 Ramesh Nair

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice (including the next paragraph) shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.