Services

A serverless service is a group of one or multiple functions and any resources they require. By grouping related functions together, it's easier to share code and resources between those functions. Services are also designed to be completely independent, which helps teams develop more quickly, without waiting for others.

Each serverless service contains two configuration files which describe it:

serverless.yaml
- Declares a serverless service
- Defines one or multiple functions in the service
- Defines the provider the service will be deployed to
- Defines events that trigger each function to execute (e.g. HTTP requests)
- Defines one set of resources (e.g. 1 AWS CloudFormation stack) required by the functions in this service
- Events listed in the events section may automatically create the resources required for the event upon deployment
- Re-usable and publicly shareable
- Contains no author-specific information
serverless.env.yaml
- Contains author-specific information (not intended for version control)
- Defines stages for this service
- Defines stage-specific variables, which allows adding dynamic values to serverless.yaml, and helps keep out sensitive information
- Provides a way to define and use environment variables

Examples

Let's take a look at a very minimal service example to see how everything works together.

Service Structure

users
  |__ lib                   // contains logic
  |__ users.js              // single handler file, requires lib
  |__ serverless.yaml
  |__ serverless.env.yaml
  |__ node_modules
  |__ package.json

serverless.yaml

service: users
provider: aws
functions:
    create:
        handler: users.create

serverless.env.yaml

vars: {}
stages:
    dev:
        vars: {}
        regions:
            us-east-1:
                vars: {}

Deployment

These deployment steps always occur first:

The serverless.yaml and serverless.env.yaml files are loaded into memory
If YAML is used, it's converted to JSON
References using Serverless variable syntax ${} or Serverless template syntax $${} are loaded
Loop through the resources property if available and collect resources for the targeted provider

Deployment On Amazon Web Services

These additional steps occur if the targeted provider is AWS:

A default AWS CloudFormation template is loaded
All of the resources in the resources property are added to that template
The AWS related plugins will run and compile the defined functions and their events to corresponding resources which will be added to the template

Deployment on Microsoft Azure

Work in progress *

Deployment on Google Cloud Platform

Work in progress *

Deployment on IBM OpenWhisk

Work in progress *

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