Serverless is an open source command line utility framework for building and deploying serverless applications. Serverless supports multiple cloud providers such as Amazon Web Services, Microsoft Azure, IBM OpenWhisk, Google Cloud Platform, Kubeless, Spotinst, Webtasks, and Fn.

In this recipe, we will use the Serverless framework to develop, deploy, invoke, check logs, and finally remove a simple hello world Lambda function on the AWS cloud platform.

Two dependencies are needed for the Serverless framework: node.js and AWS CLI. For installing AWS CLI, you may refer to the 'Deploying and Invoking Lambda with AWS CLI' recipe. You can install node using node packet as given at https://nodejs.org/en/download/package-manager.

You need to create a user for Serverless in AWS. It is a general practice to use the name serverless-admin and give administrator permission. It is not a very good practice to create users with administrator access, but currently that is the easiest way to work with Serverless. You should be careful about storing and using these credentials.

Let us create a simple Lambda using the Serverless framework:

1. Install Serverless in your machine using npm:

npm install -g serverless

2. Configure Serverless with user credentials:

serverless config credentials --provider aws --key <access key> --secret <secret access key> --profile serverless-admin

You should get a success message stating that keys were stored under the serverless-admin profile.

3. Create a Lambda function based on Java and Maven:

sls create --template aws-java-maven --path hello-world-java-maven

It creates a hello-world-java-maven folder, with pom.xml and serverless.yml files, and the src folder. You may open this Maven project in your IDE of choice. The auto-generated files looks as shown here in my IDE:

As you can see, Serverless has created a bit more than a simple hello world. Serverless takes care of most of the things we did manually, including creating a role, setting memory, setting timeout, and so on.

Add a user profile and region to serverless.yml. The region is optional if you are using the default region:

Build the jar file with:

mvn clean package

4. Deploy the jar file to AWS:

sls deploy -v

You can log in to the AWS console and verify the new Lambda service. From the log statements, you can see that Serverless framework internally makes use of CloudFormation. You can verify the same from AWS Management console.

5. Invoke the function from sls:

sls invoke -f hello -l

Option -f specifies the function name, and -l specifies that logs need to be printed to terminal. The function name to invoke is hello and is available in the serverless.yml file. You can see the output and logs on the terminal.

6. Checking logs from the CLI:

sls logs -f hello -t

Option -f specifies the function name and -t denotes to tail the logs. You can now run the invoke command from the other terminal and see the logs being printed.

7. Now, clean up everything:

sls remove

8. Log in to AWS Management console and verify that everything is cleaned up.

Serverless framework internally makes use of AWS CloudFormation for provisioning AWS resources. You can log in to Management console, go to CloudFormation service, select the stack named hello-world-java-maven-dev, and click on the Template tab for viewing the complete CloudFormation template.

You can further click on the View/Edit template in Designer option to see the template visually. The designer view of the CloudFormation template created for our example by the Serverless framework is shown here:

Serverless framework is part of the serverless.com Serverless Platform. The other two components of the serverless platform are Serverless dashboard and event gateway. Serverless framework also integrates well with other processes and tools, such as CI and CD.

• https://serverless.com/framework/docs.
• The last chapter, Chapter 10, Serverless Computing with Other Cloud Providers, Tools and Frameworks contains examples of other cloud providers.