What is AWS Lambda Link to heading

AWS Lambda is a revolutionary new way to build and run applications without the need for dedicated servers or infrastructure. With Lambda, you can simply upload your code, and AWS takes care of everything else.

At its core, Lambda is a computing service that lets you run your code in response to events and automatically manages the compute resources for you. This means you don’t need to worry about setting up servers, scaling, or even patching operating systems. AWS handles all of that for you.

For example, I want to build a service that automatically runs every 9:00 am each day. Using a server probably is not cost-effective for such a simple task. Instead of renting a real server, Lambda is a great choice in this use case cause I only pay for the time I actually use it, which might be less than 1~2 seconds each day.

But for now, let’s try to start with something simple. Let’s build a serverless function that will say “Hello world!” when it is triggered.

How to use AWS Lambda Link to heading

Here’s a step-by-step guide on how to build a Lambda function using Node.js and the Serverless Framework and deploy it to AWS:

Step 1: Install Serverless Framework Link to heading

To get started, you’ll need to install the Serverless Framework. Run the following command to install it globally:

npm install -g serverless

Step 2: Create a new Serverless service Link to heading

Create a new directory for your Serverless service and navigate to it. Then, run the following command to create a new Serverless service:

serverless create --template aws-nodejs --path mrcongliu

This will create a new directory called mrcongliu with some boilerplate code for a Serverless service using Node.js.

Step 3: Write your Lambda function Link to heading

Open the handler.js file in the mrcongliu directory and write your Lambda function code in it. Here’s an example that simply returns a string:

module.exports.hello = async (event, context) => {
  return {
    statusCode: 200,
    body: JSON.stringify({ message: "Hello, world!" })
  };
};

Step 4: Configure Serverless service Link to heading

Open the serverless.yml file in the mrcongliu directory and configure your Serverless service. Here’s an example configuration that sets the function name, runtime, and handler:

service: mrcongliu

provider:
  name: aws
  runtime: nodejs14.x

functions:
  hello:
    handler: handler.hello

Step 5: Test locally Link to heading

There are two ways to test a Lambda function, either passing in a data object to it or sending a event.json to it.

First Approach - Passing A Data Object Link to heading

If your data is small in size or you just don’t want to get too complicated into the configuration, use a data object. The syntax of passing a —data {object}looks like below.

serverless invoke local -f hello --data '{\"name\":\"mrcongliu\"}'

The reason you have to add those backslashes is because it will throw an error if you don’t.

serverless invoke local -f hello --data '{"name":"mrcongliu"}'

Second Approach - Passing An EVENT.JSON Link to heading

I would prefer this way cause I don’t need care about my input format. I simplely put everything inside event.json.

serverless invoke local -f hello -p event.json

Step 6: Deploy to dev Link to heading

Run sls deploy from the root of a service which you want to deploy.

Step 7: Test on the dev Link to heading

Three ways to test a deployed AWS Lambda function: the previous two ways plus dashboard triggering.

1. (Same as 1st for local) —data {object} Link to heading

serverless invoke -f hello -s dev -l --data '{\"name\":\"mrcongliu\"}'

In the serverless invoke command, the -l option stands for “logs”. When this option is used, it tells the Serverless Framework to stream the logs of the invoked function to the console, so that you can see the output of the function as it runs.

Here’s what the other options in the command do:

• -f hello: specifies the name of the function to invoke. In this case, the function is called “hello”.

• -s dev: specifies the name of the stage to invoke the function in. In this case, the stage is called “dev”.

• -p event.json: specifies the path to a JSON file containing the input event data for the function. The event data is passed to the function as an argument when it is invoked.

2. (Same as 2nd for local) —path event.json Link to heading

serverless invoke -f hello -s dev -l -p event.json

3. (Only for deployed functions) Dashboard Triggering Link to heading

1. Log in to the AWS Management Console and navigate to the Lambda service.
2. Click on the name of the function you want to invoke.
3. In the “Function overview” section, click on the “Test” button.
4. In the “Configure test event” dialog box, select the “Hello World” template or create a custom test event with the desired input.
5. Click on the “Create” button to create the test event.
6. Click on the “Test” button to invoke the function with the test event you just created.
7. The result of the function invocation will be displayed in the “Execution result” section at the bottom of the page.