Node.jsによるサーバーレス入門

Welcome to the world of Serverless Computing! This isn't about running code without servers; it's about not managing them yourself.

In a serverless architecture, a cloud provider (like AWS, Azure, or Google Cloud) handles all the server management, scaling, and infrastructure for you. You just focus on writing your code.

The core of serverless is often Function as a Service (FaaS). You deploy individual functions, not entire applications.

• Event-Driven: Functions run only when triggered by an event (e.g., an HTTP request, a file upload, a database change).
• Stateless: Each execution is independent; functions don't maintain state between invocations.
• Ephemeral: Functions only exist while they are executing, then they shut down.

Serverless offers compelling advantages for many applications:

• Reduced Operational Overhead: No servers to provision, patch, or scale.
• Automatic Scalability: Your functions automatically scale up or down based on demand.
• Cost Efficiency: You only pay for the compute time your code actually runs, often measured in milliseconds.
• Faster Development: Focus on business logic, not infrastructure.

Node.js is incredibly popular for serverless functions, and for good reason!

Its event-driven, non-blocking I/O model aligns perfectly with the ephemeral, event-driven nature of serverless functions. Node.js functions also tend to have very fast 'cold start' times, meaning they're ready to execute quickly.

AWS Lambda is Amazon Web Services' leading FaaS offering and one of the most widely used serverless platforms.

Lambda allows you to run code without provisioning or managing servers. You upload your code, and Lambda takes care of everything required to run and scale it with high availability.

A Node.js Lambda function typically exports a single handler function. This function receives two main arguments:

• event: An object containing data about the trigger event.
• context: An object providing runtime information about the invocation, function, and execution environment.

The function can be async or return a Promise for asynchronous operations.

Let's look at a simple "Hello World" Lambda function in Node.js. This function responds with a greeting.

Notice the statusCode and body which are common for HTTP responses via Lambda.

The event object is crucial as it contains all the input data for your function. Its structure varies based on the trigger.

If triggered by an API Gateway, it might include:

• httpMethod (e.g., 'GET', 'POST')
• path (e.g., '/hello')
• queryStringParameters
• body (for POST requests)

Lambda functions can be invoked by a wide array of AWS services. Here are some common triggers:

• API Gateway: For building RESTful APIs.
• S3 (Simple Storage Service): When objects are created or deleted in a bucket.
• DynamoDB Streams: When items in a DynamoDB table are modified.
• SNS (Simple Notification Service): For notifications and fan-out messaging.
• CloudWatch Events/EventBridge: For scheduled tasks or reacting to AWS service events.

Test your understanding of serverless computing!

Great job! You've taken your first steps into serverless computing.

• We defined serverless as focusing on code, not server management.
• Learned about FaaS (Function as a Service) as its core concept.
• Explored benefits like cost efficiency and automatic scalability.
• Understood why Node.js is a great fit for serverless.
• Got an introduction to AWS Lambda and its basic function structure.

Next, we'll dive into GraphQL API design principles!