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In this hands-on tutorial, we automate AWS Lambda deployments with Jenkins. By customizing our Lambda function code, packaging artifacts, uploading to Amazon S3, and triggering updates via the AWS CLI, we’ll achieve a seamless CI/CD pipeline.

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1. Clearing Existing Environment Variables

First, in the AWS Lambda console, navigate to your function named solar-system-function. Under Configuration, click Edit, remove all environment variables, and hit Save. We’ll inject these values dynamically in Jenkins.
The image shows an AWS Lambda console page for a function named "solar-system-function," displaying its overview, configuration options, and function details.
Removing environment variables here ensures that Jenkins controls all runtime settings securely.

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2. Preparing the Local Workspace

On your build VM or local machine, clean up any existing sandbox and checkout the latest code from the solar-system repository:
The image shows a Visual Studio Code interface with a Jenkinsfile open, displaying stages for a CI/CD pipeline. Below, there's a terminal session connected to a remote server.
cd ~
rm -rf sandbox
cd ~/solar-system
git fetch origin
git checkout main
git pull
You should see the new Jenkinsfile and updated files ready:
FileChanges
Jenkinsfile+328 insertions, updated pipeline
index.html+30 additions
integration-testing-ec2.shminor revision
package-lock.json, package.jsondependency updates
zap_ignore_rulesnew rules

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3. Adding the Lambda Deployment Stage

In Jenkinsfile, add a new stage under stages called Lambda - S3 Upload & Deploy. This stage triggers only on the main branch, modifies app.js to work in Lambda, creates a zip package, uploads it to S3, and then updates the Lambda function code: 
stage('Lambda - S3 Upload & Deploy') {
    when { branch 'main' }
    steps {
        withAWS(credentials: 'aws-s3-ec2-lambda-creds', region: 'us-east-2') {
            sh '''
                echo "----- Before Modification -----"
                tail -5 app.js

                echo "----- Modifying app.js for Lambda -----"
                sed -i "/app\\.listen(3000/s/^\\/\\///" app.js
                sed -i "s|module.exports = app;|//module.exports = app;|g" app.js
                sed -i "s|//module.exports.handler|module.exports.handler|g" app.js

                echo "----- After Modification -----"
                tail -5 app.js
            '''

            sh '''
                echo "----- Creating deployment package -----"
                zip -qr solar-system-lambda-${BUILD_ID}.zip app* package* index.html node*
                ls -ltr solar-system-lambda-${BUILD_ID}.zip
            '''

            s3Upload(
                file: "solar-system-lambda-${BUILD_ID}.zip",
                bucket: 'solar-system-lambda-bucket'
            )
        }

        sh '''
            echo "----- Updating Lambda function code -----"
            aws lambda update-function-code \
                --function-name solar-system-function \
                --s3-bucket solar-system-lambda-bucket \
                --s3-key solar-system-lambda-${BUILD_ID}.zip
        '''
    }
}
Ensure the AWS credentials you reference (aws-s3-ec2-lambda-creds) have s3:PutObject and lambda:UpdateFunctionCode permissions.

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4. Bumping the Frontend Version

Increment the frontend version number in index.html (near line 66) to v5.0 to reflect new changes:
The image shows a code editor with HTML and CSS code for styling a button and an input field. The editor interface includes a file explorer on the left and a terminal at the bottom.
After updating, save the file.

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5. AWS CLI Reference

For more details on the update-function-code command, consult the AWS CLI reference: Lambda update-function-code
The image shows a webpage from the AWS CLI Command Reference, specifically detailing the "update-function-code" command for AWS Lambda, including its description and usage instructions.
ParameterDescriptionExample
—function-nameName of the Lambda functionsolar-system-function
—s3-bucketS3 bucket holding deployment packagesolar-system-lambda-bucket
—s3-keyKey (path) to the zip in the S3 bucketsolar-system-lambda-123.zip

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6. Committing and Pushing Changes

Stage and commit your updates, then push to the main branch. This action triggers the Jenkins pipeline automatically:
The image shows a Jenkins pipeline interface with various stages of a deployment process, including building a Docker image, vulnerability scanning, and deploying to AWS. It prompts the user to decide whether to deploy to production.
git add Jenkinsfile index.html
git commit -m "Add Lambda deployment stage and bump frontend version"
git push origin main
Follow any manual approval prompts in Jenkins to proceed.

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7. Validating the Deployment in S3

After the build completes, verify that the new ZIP artifact appears in your S3 bucket:
The image shows an Amazon S3 bucket interface with two zip files named "solar-system-lambda-2.zip" and "solar-system-lambda.zip," both 9.9 MB in size. The files are listed with details such as last modified date and storage class.

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8. Troubleshooting: Missing Environment Variables

If you encounter an Internal Server Error, it often indicates missing environment variables. Check CloudWatch logs to debug:
The image shows an AWS CloudWatch log screen displaying an error message related to a Mongoose connection issue, indicating that the URI parameter must be a string but received "undefined".
In app.js you’ll find: 
// app.js (excerpt)
const mongoose = require('mongoose');
// ...
mongoose.connect(process.env.MONGO_URI, {
  user: process.env.MONGO_USERNAME,
  pass: process.env.MONGO_PASSWORD,
  useNewUrlParser: true,
  useUnifiedTopology: true
}, (err) => {
  if (err) {
    console.error("MongoDB Connection Error:", err);
  } else {
    console.log("MongoDB Connection Successful");
  }
});
Here, process.env.MONGO_URI, MONGO_USERNAME, and MONGO_PASSWORD must be supplied by Jenkins.
Without proper environment variables, your Lambda function will fail to connect to MongoDB.

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9. Next Steps: Injecting Environment Variables via Jenkins

To address missing credentials, update your pipeline block in Jenkinsfile. Add an environment section with secure credential bindings: 
pipeline {
    agent any

    environment {
        MONGO_URI          = credentials('mongo-db-uri')
        MONGO_USERNAME     = credentials('mongo-db-username')
        MONGO_PASSWORD     = credentials('mongo-db-password')
        SONAR_SCANNER_HOME = tool 'sonarqube-scanner-610'
        GITEA_TOKEN        = credentials('gitea-api-token')
    }

    stages {
        // … existing stages … 
        stage('Lambda - S3 Upload & Deploy') { … }
    }
}
By following these steps, you’ll ensure your AWS Lambda deployments are automated, secure, and maintainable.

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