Cron Jobs

Add a cron job to your SST app.

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Overview

SST makes it very easy to add serverless cron jobs to your app.

1. Add a construct and define the schedule
2. Create the function that'll get run

Let's look at how to do this in detail.

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Get started

Start by creating a new SST + Next.js app by running the following command in your terminal. We are using Next.js for this example but you can use your favorite frontend.

npx create-sst@latest --template standard/nextjs

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Add the construct

Add the construct to your stacks.

stacks/Default.ts

new Cron(stack, "cron", {
  schedule: "rate(1 minute)",
  job: "packages/functions/src/cron.handler",
});

This defines a cron job that'll run every minute and points to the function that will be invoked.

info

The fastest rate a cron job can be run is every minute.

Make sure to import the Cron construct.

stacks/Default.ts

- import { StackContext, NextjsSite } from "sst/constructs";
+ import { Cron, StackContext, NextjsSite } from "sst/constructs";

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Add the handler

Let's add the function that'll be invoked. Create a file in packages/functions/src/cron.ts.

packages/functions/src/cron.ts

export async function handler() {
  console.log("Running my cron job");
}

Once your app updates, you'll notice the logs being printed out every minute in your terminal.

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Cron schedule

There are a couple of ways to specify the schedule of a cron jon.

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Rate expressions

Rate expressions are the simplest way to do it. Here are some sample rate expressions:

• rate(1 minute)
• rate(5 minutes)
• rate(1 hour)
• rate(12 hours)
• rate(1 day)
• rate(7 days)

If the value is equal to 1, then the unit must be singular. If the value is greater than 1, the unit must be plural.

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Cron expressions

Alternatively, you can specify a cron expression to have it run at specific times, ie. every day at 12:00pm.

schedule: "cron(0 12 * * ? *)",

info

All cron expressions use the UTC+0 time zone.

Here are some example cron expressions:

Minutes	Hours	Day of month	Month	Day of week	Year	Description
0	10	*	*	?	*	Run at 10:00 am every day
15	12	*	*	?	*	Run at 12:15 pm every day
0	18	?	*	MON-FRI	*	Run at 6:00 pm every Monday through Friday
0	8	1	*	?	*	Run at 8:00 am every 1st day of the month
0/15	*	*	*	?	*	Run every 15 minutes
0/10	*	?	*	MON-FRI	*	Run every 10 minutes Monday through Friday
0/5	8-17	?	*	MON-FRI	*	Run every 5 minutes Monday through Friday between 8:00 am and 5:55 pm
0/30	20-2	?	*	MON-FRI	*	Run every 30 minutes Monday through Friday between 10:00 pm on the starting day to 2:00 am on the following day

You can read more about the cron expressions syntax.

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And that's it! You can now add cron jobs to your app. If your function needs to run for longer than the Lambda timeout, you can trigger a long running job.