#OpenWhisk - Introduction

The Serverless Framework helps you develop and deploy serverless applications using Apache OpenWhisk. 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 than other application frameworks because:

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

#Core Concepts

Here are the Framework's main concepts and how they pertain to Apache OpenWhisk…

#Functions

A Function is an Apache OpenWhisk Action. It's an independent unit of deployment, like a microservice. It's 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

You can perform multiple jobs in your code, but we don't recommend doing that without good reason. Separation of concerns is best and the Framework is designed to help you easily develop and deploy Functions, as well as manage lots of them.

#Events

Anything that triggers an Apache OpenWhisk Action to execute is regarded by the Framework as an Event. Events are platform events on Apache OpenWhisk such as:

• An API Gateway HTTP endpoint (e.g., for a REST API)
• A NoSQL database update (e.g., for a user profile)
• A scheduled timer (e.g., run every 5 minutes)
• A Kafka queue message (e.g., a message)
• A Webhook fires (e.g., Github project update)
• And more...

When you define an event for your Apache OpenWhisk Action in the Serverless Framework, the Framework will automatically translate this into Triggers and Rules needed for that event and configure your functions to listen to it.

#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. It's where you define your Functions, the Events that trigger them, and the Resources your Functions use, all in one file by default entitled serverless.yml (or serverless.json or serverless.js). It looks like this:

# serverless.yml

service: users

functions: # Your "Functions"
  usersCreate:
    events: # The "Events" that trigger this function
      - http: post /users/create
  usersDelete:
    events:
      - http: delete /users/delete

When you deploy with the Framework by running serverless deploy, everything in serverless.yml (or the file specified with the --config option) is deployed at once.

#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-plugin-identifier
  - serverless-another-plugin