README

async-cron

Simple cron job runner for Node that handles async functions and uses a Mutex that keeps the same job from running more than once simultaneously.

Installation

npm install @simpleview/async-cron

Example

const { Job } = require("@simpleview/async-cron");

const job = new Job({
    schedule : "*/5 * * * * *"
}, async function() {
    const results = await doSomething();
    return someResult;
});

// Required: Handle errors, or they will be black-holed resulting in not knowing that your crons are failing
job.on("error", function(e) {
    console.log("Cron Error", e);
});

// Not required: if you care about the returned result from a cronJob, you can do something with it here
job.on("result", function(result) {
    
});

// Starts the job running the background
job.start();

Error Handling

If your job errors, the error will be blackholed unless you subscribe to the error handler.

job.on("error", function(e) {
    // do something with the error
});

If you want to differentiate errors from the job running from code errors, you can check the error code.

const { Job, E_RUNNING } = require("@simpleview/async-cron");

const job = new Job(...args...);

job.on("error", function(e) {
    if (e.code === E_RUNNING) {
        console.log("Still running!");
    } else {
        console.log("An actual code problem!");
    }
});

Package API

Job

Job represents a single cron job.

args
- schedule - string - The schedule in cron-parser syntax.
fn - function or async function - The function that will execute your job. It should either run fully synchronously, or be an async method/promise-based method. Do not utilize callbacks here, or else the async locking mechanism will not function properly. When this function returns, the job must be complete.

Job.start()

Starts the job running in the background.

Job.stop()

Stops the job. This will not halt functions that are currently executing at this very moment, but it will present new runs from queuing up.

Job.run()

Manually executes the job. If the job errors, then this will throw, this includes throwing if the job is currently executing.

const result = await job.run();

Job.isRunning()

Check if the job is currently running.

const isRunning = job.isRunning();

E_RUNNING

Symbol reference for error.code when an Error is thrown due to an a job already running. See error handling.

Usage no npm install needed!