Serverless Framework Concepts

The Serverless Framework helps you develop and deploy AWS Lambda functions, along with the AWS infrastructure resources they require. It's a CLI that offers structure, automation and best practices out-of-the-box, allowing you to focus on building sophisticated, event-driven, serverless architectures, comprised of Functions and Events.

The Serverless Framework is different from other application frameworks because:

  • It manages your code as well as your infrastructure
  • It supports multiple languages (Node.js, Python, Java, and more)

Here are the Framework's main concepts and how they pertain to AWS and Lambda.

Functions

The code of a serverless application is deployed and executed in AWS Lambda functions.

Each function is an independent unit of execution and deployment, like a microservice. A function is merely code, deployed in the cloud, that is most often written to perform a single job such as:

  • Saving a user to the database
  • Processing a file in a database
  • Performing a scheduled task

Learn more on defining functions

Events

Functions are triggered by events. Events come from other AWS resources, for example:

  • An HTTP request on an API Gateway URL (e.g. for a REST API)
  • A new file uploaded in an S3 bucket (e.g. for an image upload)
  • A CloudWatch schedule (e.g. run every 5 minutes)
  • A message in an SNS topic
  • A CloudWatch alert
  • And more...

When you configure an event on a Lambda function, Serverless Framework will automatically create the infrastructure needed for that event (e.g. an API Gateway endpoint) and configure your functions to listen to it.

Learn more on defining function events

Resources

Resources are AWS infrastructure components which your functions use such as:

  • A DynamoDB table (e.g. for saving users/posts/comments data)
  • An S3 bucket (e.g. for saving images or files)
  • An SNS topic (e.g. for sending messages asynchronously)
  • Anything that can be defined in CloudFormation is supported by the Serverless Framework

Serverless Framework can deploy functions and their events, but also AWS resources.

Learn more on defining AWS resources

Services

A service is the Framework's unit of organization. You can think of it as a project file, though you can have multiple services for a single application.

A service is configured via a serverless.yml file where you define your functions, events and AWS resources to deploy. It looks like this:

service: users

functions: # Your "Functions"
  usersCreate:
    events: # The "Events" that trigger this function
      - httpApi: 'POST /users/create'
  usersDelete:
    events:
      - httpApi: 'DELETE /users/delete'

resources: # The "Resources" your "Functions" use. Raw AWS CloudFormation goes in here.

When deploying with the Framework via serverless deploy, everything in the configuration file is deployed at once.

Learn more on configuring a service

Alternative configuration format

In case you need more flexibility, you can also define the service configuration in JSON (serverless.json), JavaScript (serverless.js) or TypeScript (serverless.ts).

While Serverless Framework is language-agnostic, projects written in Node.js can benefit from using the same language all around. When using JavaScript or TypeScript, the file must export the configuration as a JS object, for example:

'use strict'

// serverless.js

module.exports = {
  service: 'users',
  functions: {
    usersCreate: {
      events: [
        {
          httpApi: 'POST /users/create',
        },
      ],
    },
    // ...
  },
  resources: {},
}
// Requiring @types/serverless in your project package.json
import type { Serverless } from 'serverless/aws'

// serverless.ts

const serverlessConfiguration: Serverless = {
  service: 'users',
  functions: {
    usersCreate: {
      events: [
        {
          httpApi: 'POST /users/create',
        },
      ],
    },
    // ...
  },
  resources: {},
}

module.exports = serverlessConfiguration

Note: when deploying using a serverless.ts file, ts-node needs to be installed separately as a dev dependency.

For the sake of simplicity, most examples in the documentation refer to the serverless.yml format. However, all functionalities work with the other available service file formats.

Plugins

You can overwrite or extend the functionality of the Framework using plugins. Every serverless.yml can contain a plugins: property, which features multiple plugins.

# serverless.yml

plugins:
  - serverless-offline
  - serverless-secrets

Learn more about plugins

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Serverless Framework Concepts

The Serverless Framework helps you develop and deploy AWS Lambda functions, along with the AWS infrastructure resources they require. It's a CLI that offers structure, automation and best practices out-of-the-box, allowing you to focus on building sophisticated, event-driven, serverless architectures, comprised of Functions and Events.

The Serverless Framework is different from other application frameworks because:

  • It manages your code as well as your infrastructure
  • It supports multiple languages (Node.js, Python, Java, and more)

Here are the Framework's main concepts and how they pertain to AWS and Lambda.

Functions

The code of a serverless application is deployed and executed in AWS Lambda functions.

Each function is an independent unit of execution and deployment, like a microservice. A function is merely code, deployed in the cloud, that is most often written to perform a single job such as:

  • Saving a user to the database
  • Processing a file in a database
  • Performing a scheduled task

Learn more on defining functions

Events

Functions are triggered by events. Events come from other AWS resources, for example:

  • An HTTP request on an API Gateway URL (e.g. for a REST API)
  • A new file uploaded in an S3 bucket (e.g. for an image upload)
  • A CloudWatch schedule (e.g. run every 5 minutes)
  • A message in an SNS topic
  • A CloudWatch alert
  • And more...

When you configure an event on a Lambda function, Serverless Framework will automatically create the infrastructure needed for that event (e.g. an API Gateway endpoint) and configure your functions to listen to it.

Learn more on defining function events

Resources

Resources are AWS infrastructure components which your functions use such as:

  • A DynamoDB table (e.g. for saving users/posts/comments data)
  • An S3 bucket (e.g. for saving images or files)
  • An SNS topic (e.g. for sending messages asynchronously)
  • Anything that can be defined in CloudFormation is supported by the Serverless Framework

Serverless Framework can deploy functions and their events, but also AWS resources.

Learn more on defining AWS resources

Services

A service is the Framework's unit of organization. You can think of it as a project file, though you can have multiple services for a single application.

A service is configured via a serverless.yml file where you define your functions, events and AWS resources to deploy. It looks like this:

service: users

functions: # Your "Functions"
  usersCreate:
    events: # The "Events" that trigger this function
      - httpApi: 'POST /users/create'
  usersDelete:
    events:
      - httpApi: 'DELETE /users/delete'

resources: # The "Resources" your "Functions" use. Raw AWS CloudFormation goes in here.

When deploying with the Framework via serverless deploy, everything in the configuration file is deployed at once.

Learn more on configuring a service

Alternative configuration format

In case you need more flexibility, you can also define the service configuration in JSON (serverless.json), JavaScript (serverless.js) or TypeScript (serverless.ts).

While Serverless Framework is language-agnostic, projects written in Node.js can benefit from using the same language all around. When using JavaScript or TypeScript, the file must export the configuration as a JS object, for example:

'use strict'

// serverless.js

module.exports = {
  service: 'users',
  functions: {
    usersCreate: {
      events: [
        {
          httpApi: 'POST /users/create',
        },
      ],
    },
    // ...
  },
  resources: {},
}
// Requiring @types/serverless in your project package.json
import type { Serverless } from 'serverless/aws'

// serverless.ts

const serverlessConfiguration: Serverless = {
  service: 'users',
  functions: {
    usersCreate: {
      events: [
        {
          httpApi: 'POST /users/create',
        },
      ],
    },
    // ...
  },
  resources: {},
}

module.exports = serverlessConfiguration

Note: when deploying using a serverless.ts file, ts-node needs to be installed separately as a dev dependency.

For the sake of simplicity, most examples in the documentation refer to the serverless.yml format. However, all functionalities work with the other available service file formats.

Plugins

You can overwrite or extend the functionality of the Framework using plugins. Every serverless.yml can contain a plugins: property, which features multiple plugins.

# serverless.yml

plugins:
  - serverless-offline
  - serverless-secrets

Learn more about plugins