AWS SAM 简介

Hello! Today we'll explore AWS SAM, the Serverless Application Model. It's an open-source framework designed to help you build serverless applications on AWS more efficiently.

Think of SAM as a powerful extension to AWS CloudFormation, specifically tailored for serverless resources.

AWS CloudFormation is a robust service for defining infrastructure as code. However, building serverless applications directly with CloudFormation can be quite verbose.

• A simple AWS Lambda function often requires defining the Lambda resource itself, an IAM role with permissions, and possibly an API Gateway endpoint.
• This can lead to many lines of configuration for even basic setups.

AWS SAM aims to simplify this complexity. It provides a shorthand syntax to define common serverless resources.

Instead of defining multiple CloudFormation resources for a single serverless component, SAM lets you define it with just one simplified resource type.

Using AWS SAM brings several advantages to your serverless development workflow:

• Reduced Boilerplate: Define serverless functions, APIs, and databases with fewer lines of code.
• Local Testing: Test your Lambda functions and API Gateway locally before deploying to AWS.
• Simplified Deployments: The SAM CLI handles packaging, uploading, and deploying your application seamlessly.
• CloudFormation Power: It's built on CloudFormation, so you still get its reliability and features.

Your serverless application's infrastructure is defined in a SAM template, which is typically a YAML or JSON file. The most crucial part that tells CloudFormation to use SAM's simplified syntax is the Transform section.

This Transform line instructs CloudFormation to expand SAM's shorthand into full CloudFormation resources before deployment.

Let's look at a very basic SAM template. This YAML defines a simple 'Hello World' Lambda function. Notice how concise it is compared to what raw CloudFormation would require for the same setup!

Let's break down that template:

• Transform: AWS::Serverless-2016-10-31: This tells CloudFormation to process the SAM specific syntax.
• Type: AWS::Serverless::Function: This is a SAM resource type. It automatically creates the Lambda function, an execution IAM role, and necessary permissions.
• Handler, Runtime, CodeUri: These are standard AWS Lambda properties, specifying where your code is, its language, and the entry point.

While SAM templates define your resources, the SAM Command Line Interface (CLI) is your primary tool for interacting with your serverless application.

The SAM CLI allows you to:

• Build your application (e.g., package dependencies).
• Test your Lambda functions locally.
• Deploy your application to AWS.

A typical SAM development workflow involves these high-level steps:

1. Write your Lambda function code (e.g., Python, Node.js).
2. Define your application's resources in a SAM template (YAML/JSON).
3. Use sam build to prepare your application for deployment.
4. Use sam deploy to push your application to AWS.

The SAM CLI handles all the underlying CloudFormation magic!

Based on what we've learned, what is the primary purpose of AWS SAM?

You've just been introduced to AWS SAM! We learned that SAM simplifies serverless development by providing a concise way to define resources, building on top of CloudFormation.

You also saw a basic SAM template and learned about the powerful SAM CLI.

Next, we'll dive deeper into defining various serverless resources within your SAM templates, including functions, APIs, and databases!