Best Practices for Working with Strapi Cron Jobs

Strapi - Apr 10 '23 - - Dev Community

Strapi Cron Jobs are automated tasks that can be scheduled to run at specific intervals. Cron jobs can be used for a variety of tasks such as cleaning up old data, sending emails, generating reports, and more.

This article will cover the required steps to set up a Cron Job natively in Strapi and then also how to set up a Cron that is external to Strapi using both GitHub actions and Linux Crontab.

While Strapi's Cron feature works well for setting up a Cron Job in a simple Strapi project, it falls short when needing to scale Strapi horizontally. When scaling Strapi horizontally but still using the built-in Strapi Cron, Strapi will fire a Cron Job on every instance simultaneously. This can cause race conditions and unintended side effects.

Read on to learn how to set up a Cron Jon in Strapi and avoid issues with Cron Jobs when horizontally scaling.

Prerequisites

Before you can jump into this content, you need to have a basic understanding of the following.

  1. Basic knowledge of JavaScript
  2. A Node.js ready environment
  3. Basic understanding of Strapi - get started here.

What is Strapi?

Strapi is an open-source headless CMS based on Node.js used to develop and manage content using a Restful API and/or GraphQL.

With Strapi, we can scaffold our API faster and consume the content via APIs using any HTTP client or GraphQL enabled frontend.

Scaffolding a Strapi project

Scaffolding a new Strapi project is very simple and works precisely as installing a new frontend framework.

We are going to start by running the following commands and testing them out in our default browser.

npx create-strapi-app strapi-api --quickstart
# OR
yarn create strapi-app strapi-api --quick start
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The command above will scaffold a new Strapi project in your specified directory.

Next, run yarn build to build your app and yarn develop to run the new project if it doesn't start automatically.

The last command will open a new tab with a page to register your new admin of the system. Fill out the form and click the submit button to create a new Admin.

Creating a Cron Job in Strapi

To create a Cron Job in Strapi there are two files that we need to add/modify. First, we will create a cron-task.js file and then enable the cron job by editing the server.js file. If you need more information on using Cron jobs in Strapi you can find the Cron Job documentation here.

For this demonstration of Strapi Cron Jobs, we will assume that we have a blog set up in Strapi, the code for the demonstration is here. What we want to achieve is to receive a notification daily (or at a certain cadence) to let us know how many articles have been published. This could be useful if you have a writer that is writing articles and you want to keep track of how many they have produced and published.

The code below illustrates what should be in the cron-task.js file that you create in your config folder. This file has two important properties, one is the task that gets run by the Cron and the other is the timer for the Cron (how often the task should be run). The logic in the task gets the count of all published posts and then logs that out and sends an email. The schedule property is set so that this Cron runs once every minute (in this case for demo purposes) but in our real world application we would want to adjust this to a daily frequency.

module.exports = {
  postCountEmail: {
    task: async ({ strapi }) => {
      const count = await strapi.entityService.count("api::article.article", {
        publicationState: "live",
      });

      console.log(
        `Sending email with published article count ${count} (run by Strapi cron)`
      );

      try {
        await strapi.plugins.email.services.email.send({
          to: "brayden@gmail.com",
          from: "noreply@strapi.com",
          subject: "Post count",
          text: `You have ${count} published articles`,
          html: `You have ${count} published articles`,
        });
      } catch (err) {
        // Commented out for demo purposes
        //console.error(err);
      }
    },
    options: {
      // Every minute
      rule: "*/1 * * * *",
    },
  },
};
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Now to activate the Cron we just created we have to edit the server.js file to add the cron property. The code snippet for this is below.

const crontTasks = require("./cron-tasks");

module.exports = ({ env }) => ({
  host: env("HOST", "0.0.0.0"),
  port: env.int("PORT", 1337),
  cron: {
    enabled: env.bool("CRON_ENABLED", true),
    tasks: crontTasks,
  },
  app: {
    keys: env.array("APP_KEYS"),
  },
  webhooks: {
    populateRelations: env.bool("WEBHOOKS_POPULATE_RELATIONS", false),
  },
});
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To test out this Cron, we can run the following: npm run strapi develop

Once the Cron runs, we will see the output in the console, as shown below.
Cron Job console output

So far, we have learned how to set up Cron jobs natively in Strapi. The only issue with running Cron jobs in Strapi like this is if we decide to scale our Strapi instances horizontally.

When horizontally scaling, typically, several instances of Strapi will be running on different servers, all behind a load balancer. While the load balancer distributes the incoming requests to one instance at a time, the Strapi Cron will run on all instances at once. When this happens, each of the running Strapi instances will race to run the same Cron at the same time. This can cause all kinds of problems.

In our demonstration scenario, this would cause our server to send out several emails for each run of the Cron job. We definitely don't want to receive 12 emails just because we have 12 Strapi instances running. So how can we ensure that this does not happen?

Horizontally Scaling Strapi with External Cron Jobs

Since we can not use built-in Strapi Cron jobs while horizontally scaling Strapi, we will move this Cron job outside of Strapi. An external service will trigger on a Cron schedule which will then need a way to call an endpoint in Strapi. We can create our custom route that when called will then trigger a custom controller to be run. This custom controller will replace the logic we use in our cron-task.js file above.

First, let's create the custom route in Strapi. To do this we need to create a new file under the src/api/article/routes folder. We will name this file 0-custom-article.js. The reason we prefix the file name with a 0 so that this route gets loaded before the built-in routes. The code required in this file to create a custom route in Strapi is shown below.

module.exports = {
  routes: [
    {
      method: "GET",
      path: "/articles/cron/published-count",
      handler: "api::article.article.cronPublishedCount",
    },
  ],
};
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The above custom route points to the cronPublishedCount method in our custom controller. Next, we will create this custom controller by adding it to the existing article.js controller file which is located in the src/api/article/controller folder. The logic we will add to this file basically does the exact same thing that our built-in Strapi Cron task did.

"use strict";

/**
 *  article controller
 */

const { createCoreController } = require("@strapi/strapi").factories;

module.exports = createCoreController("api::article.article", ({ strapi }) => ({
  async cronPublishedCount(ctx) {
    const count = await strapi.entityService.count("api::article.article", {
      publicationState: "live",
    });

    console.log(
      `Sending email with published article count ${count} (run by external cron)`
    );

    try {
      await strapi.plugins.email.services.email.send({
        to: "brayden@notarealemail123.com",
        from: "noreply@strapi.com",
        subject: "Post count",
        text: `You have ${count} published articles`,
        html: `You have ${count} published articles`,
      });
    } catch (err) {
      // Commented out for demo purposes
      // console.error(err);
    }
    ctx.status = 200;
  },
}));
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Now that we have our custom route and controller built in Strapi, we have to call this route externally from Strapi. There are many ways to accomplish this but we will look at two popular options.

Using Crontab

The first simple way to schedule a Cron, which will call an endpoint, is to use Crontab. If you're on a Linux machine or you have a Linux VPS, Crontab is already built in. All you have to do is run the command crontab -e to open the Crontab file for editing. In this file, we want to make a curl request to that custom route in Strapi in order to trigger our custom controller. See the snippet below for what this would look like.

*/1 * * * * curl -s https://your-publi-url.com/api/articles/cron/published-count
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Don’t forget to make your Strapi custom route available to the public in the Strapi Admin. Showing the picture below.
Strapi permission settings

You should now have a running Cron that is external to Strapi. If you run your Strapi project in development mode and then forward a tunnel with something like Ngrok to your local development machine, you should be seeing your Cron working and logging.

Using GitHub Actions

Another option for setting up a Cron job external to Strapi is using GitHub actions. GitHub actions can be set up to be triggered on a Cron schedule. Since GitHub is a job run on a Linux machine, you can have that job run Linux commands. We simply need to run the curl command to call our custom Strapi route. If your code is hosted on GitHub, you simply need to create a file with contents similar to the snippet below that is in the following path: .github/workflows/cron.yml

name: post-count-cron
on:
  schedule:
    - cron: ‘*/5 * * * *'
  workflow_dispatch:
jobs:
  cron:
    runs-on: ubuntu-latest
    steps:
      - name: Get request to the custom Strapi route
        run: |
          curl -s https://your-publi-url.com/api/articles/cron/published-count
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Since GitHub actions only allow you to run at a minimum interval of 5 minutes, we have used 5 minutes as the example above.

Wrap Up

This article provided information on the best practices for working with Cron Jobs in Strapi. If you need to run a single instance of Strapi, you can easily set up the built-in Strapi Cron Jobs. When you need to scale your Strapi instances horizontally, you now have a couple of available options.

If you prefer to follow a video tutorial for setting up Strapi Cron jobs, check our YouTube channel.

Thanks for reading through this article and if you have any other questions, please comment below!

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