Stages in Serverless Framework

Serverless Framework allows you to create stages for your project to deploy to. Stages are useful for creating environments for testing and development. Typically you create a staging environment that is an independent clone of your production environment. This allows you to test and ensure that the version of code that you are about to deploy is good to go.

In this chapter we will take a look at how to configure stages in serverless. Let’s first start by looking at how stages can be implemented.

How Is Staging Implemented?

There are a couple of ways to set up stages for your project:

Using the API Gateway built-in stages

You can create multiple stages within a single API Gateway project. Stages within the same project share the same endpoint host, but have a different path. For example, say you have a stage called prod with the endpoint:
```
https://abc12345.execute-api.us-east-1.amazonaws.com/prod
```
If you were to add a stage called dev to the same API Gateway API, the new stage will have the endpoint:
```
https://abc12345.execute-api.us-east-1.amazonaws.com/dev
```
The downside is that both stages are part of the same project. You don’t have the same level of flexibility to fine tune the IAM policies for stages of the same API, when compared to tuning different APIs. This leads to the next setup, each stage being its own API.
Separate APIs for each stage

You create an API Gateway project for each stage. Let’s take the same example, your prod stage has the endpoint:
```
https://abc12345.execute-api.us-east-1.amazonaws.com/prod
```
To create the dev stage, you create a new API Gateway project and add the dev stage to the new project. The new endpoint will look something like:
```
https://xyz67890.execute-api.us-east-1.amazonaws.com/dev
```
Note that the dev stage carries a different endpoint host since it belongs to a different project. This is the approach Serverless Framework takes when configuring stages for your Serverless project. We will look at this in detail below.
Separate AWS account for each stage

Just like how having each stage being separate APIs give us more flexibility to fine tune the IAM policy. We can take it a step further and create the API project in a different AWS account. Most companies don’t keep their production infrastructure in the same account as their development infrastructure. This helps reduce any cases where developers accidentally edit/delete production resources. We go in to more detail on how to deploy to multiple AWS accounts using different AWS profiles in the Configure Multiple AWS Profiles chapter.

Deploying to a Stage

Let’s look at how the Serverless Framework helps us work with stages. As mentioned above, a new stage is a new API Gateway project. To deploy to a specific stage, you can either specify the stage in the serverless.yml.

service: service-name

provider:
  name: aws
  stage: dev

Or you can specify the stage by passing the --stage option to the serverless deploy command.

$ serverless deploy --stage dev

Stage Variables in Serverless Framework

Deploying to stages can be pretty simple but now let’s look at how to configure our environment variables so that they work with our various stages. We went over the concept of environment variables in the chapter on Serverless Environment Variables. Let’s extend that to specify variables based on the stage we are deploying to.

Let’s take a look at a sample serverless.yml below.

service: service-name

custom:
  myStage: ${opt:stage, self:provider.stage}
  myEnvironment:
    MESSAGE:
      prod: "This is production environment"
      dev: "This is development environment"

provider:
  name: aws
  stage: dev
  environment:
    MESSAGE: ${self:custom.myEnvironment.MESSAGE.${self:custom.myStage}}

There are a couple of things happening here. We first defined the custom.myStage variable as ${opt:stage, self:provider.stage}. This is telling Serverless Framework to use the --stage CLI option if it exists. And if it does not, then use the default stage specified by provider.stage. We also define the custom.myEnvironment section. This contains the value for MESSAGE defined for each stage. Finally, we set the environment variable MESSAGE as ${self:custom.myEnvironment.MESSAGE.${self:custom.myStage}}. This sets the variable to pick the value of self:custom.myEnvironment depending on the current stage defined in custom.myStage.

You can easily extend this format to create separate sets of environment variables for the stages you are deploying to.

And we can access the MESSAGE in our Lambda functions via process.env object like so.

export function main(event, context, callback) {
  callback(null, { body: process.env.MESSAGE });
}

Hopefully, this chapter gives you a quick idea on how to set up stages in your Serverless project.

How Is Staging Implemented?

Deploying to a Stage

Stage Variables in Serverless Framework

SST Guide