Fellas, let's continue exploring serverless services now with Digital Ocean cloud provider. This is a more useful practice than the previous ones, we will deploy a function scheduled to run every X minutes to reach a Website/API via HTTP. In case the service is down or the response is not the expected one we will send an email to selected recipients to inform the downtime of the service.

Requirements:

• DigitalOcean account and a personal access token

• Install and configure the doctl (DO CLI) tool so we can authenticate and run commands

• Generate the function scaffolded template

• For the email sending you will need AWS SES API keys as well as an authorized sender (this may be optional, or you can adapt the code to use another mail provider).

Assuming you already met the requirements let's start coding.

1. Run npm init to generate a package.json file

2. Install the axios (required) and aws sdk (optional) packages

    npm install --save axios 
    npm install --save aws-sdk
   

3. index.js file

    const axios = require("axios");
    const aws = require("./aws_ses");
   
    async function main(args) {
      const response = await axios.get("https://google.com");
   
      if (response.status !== 200) {
        await aws.sendEmail(
          [
            "recipient-email@gmail.com",
          ],
          "Website Monitor"
        );
        return {success: false, message: "Service is down!"};
      }
   
      return {success: true, message: "Service is up and running"};
    }
   
    exports.main = main;
   

4. aws-ses.js file

    const aws_sdk = require("aws-sdk");
   
    const AWS_SES = new aws_sdk.SES({
      accessKeyId: process.env.SES_ACCESS_KEY,
      secretAccessKey: process.env.SES_SECRET_KEY,
      region: process.env.SES_REGION,
    });
   
    async function sendEmail(recipientEmails, serviceName) {
      let params = {
        Source: 'your-authorized-sending-email@gmail.com',
        Destination: {
          ToAddresses: [
            ...recipientEmails
          ],
        },
        ReplyToAddresses: [],
        Message: {
          Body: {
            Html: {
              Charset: 'UTF-8',
              Data: `<h3>Hello admin, the service ${serviceName} is not working as expected. <br> The monitor failed at 
                    ${new Date().toLocaleDateString()} ${new Date().toLocaleTimeString()}. Please check if everything is OK.</h3>`,
            },
          },
          Subject: {
            Charset: 'UTF-8',
            Data: `Website Monitor: Service not working properly`,
          }
        },
      };
      return AWS_SES.sendEmail(params).promise();
    }
   
    exports.sendEmail = sendEmail;
   

5. project.yml file

    parameters: {}
    environment:
      SES_ACCESS_KEY: "${SES_ACCESS_KEY}"
      SES_SECRET_KEY: "${SES_SECRET_KEY}"
      SES_REGION: "${SES_REGION}"
    packages:
        - name: sample
          shared: false
          environment: {}
          parameters: {}
          annotations: {}
          functions:
            - name: "hello"
              triggers:
                - name: "5 Minutes Trigger"
                  sourceType: scheduler
                  sourceDetails:
                    cron: "*/5 * * * *"
              binary: false
              main: ""
              runtime: nodejs:18
              web: true
              webSecure: false
              parameters: { }
              environment: { }
              annotations: { }
              limits:
                memory: 512
                timeout: 6000
   

   This file allows us to set more function configurations like the memory we need, the timeout, access via web, authentication with token, runtime, triggers and more. For this specific example, we are deploying a javascript function whose runtime is node v18, with 512 MB of memory and a timeout of 6s. Also, it has a scheduler for automatic execution running every 5 minutes. Here you have the full reference https://docs.digitalocean.com/products/functions/reference/project-configuration/

6. .env file

    SES_ACCESS_KEY=
    SES_SECRET_KEY=
    SES_REGION=
   

   It is important to place the .env file in the root of the project

7. Project structure

    example-project
    ├── project.yml
    └── .env
    └── packages
        └── example-package
            └── example-function.php
   

8. Up to this point with everything in place we are ready to deploy our function

     doctl serverless deploy <example-project>
   

   This command will deploy every function for every package you have in the <example-project>. You could use the flags --include or --exclude to specify packages/functions. Full reference here: https://docs.digitalocean.com/reference/doctl/reference/serverless/deploy/

9. After a successful deployment head to the DO console, and you should be able to see a list similar to this one under Functions page:

   

10. Click the function name to see details, once there you can run the function from here and pass parameters. You can also see the triggers if exist and the settings we defined in the project.yml file.

    

We did it! A basic HTTP monitor using Digital Ocean serverless functions! 💫

Feel free to leave your comments or suggestions.