How to Override and Add Configuration Values in the Serverless Framework

This is a summary of the points I got stuck on when overriding settings in the Serverless Framework.

Basically, I referred to the official documentation below while testing a few implementation patterns.

Let’s try configuring things using environment variables as an example.

Environment Variables

Common Setting Across Stages

provider:
  environment:
    key: 'hello,world'

With the configuration above, the environment variable is set as follows.

• key: hello,world

Overriding a Single Value

Reference: Overwriting Variables

provider:
  name: openwhisk
  stage: dev

custom:
  myStage: ${opt:stage, self:provider.stage}

functions:
  trigger:
    environment:
      key: ${self:custom.myStage}

With the configuration above, the environment variable settings after deployment are as follows.

• When deployed with sls deploy
  • key: dev
• When deployed with sls deploy --stage hoge
  • key: hoge

Adding and Overriding the environment per Stage

The default settings are specified in provider.environment, and the per-stage settings can be added or overridden via self:custom.${self:provider.stage}.environment.

provider:
  environment:
    project: ${self:custom.${self:provider.stage}.project}
    slackChannel: ${self:custom.${self:provider.stage}.slack.channel}
    key: 'hello,world'

custom:
  hoge:
    project: hoge
    slack:
      channel: '#hoge'
  moge:
    project: moge
    slack:
      channel: '#moge'
    environment:
      key: 'moge-key'
      key2: 'moge-key2'

functions:
  trigger:
    environment: ${self:custom.${self:provider.stage}.environment, self:provider.environment}

With the configuration above, the environment variable settings after deployment are as follows.

• When deployed with sls deploy --stage hoge
  • project: hogeproject
  • slackChannel: #hoge
  • key: hello,world
• When deployed with sls deploy --stage moge
  • project: hogeproject
  • slackChannel: #hoge
  • key: moge-key <-- updated
  • key2: moge-key2 <-- added

The reason for overriding functions.trigger.environment is that if you write it as follows,

functions:
  trigger:
    # environment: ${self:custom.${self:provider.stage}.environment, self:provider.environment}
    environment: ${self:custom.${self:provider.stage}.environment}

there is no self:custom.hoge.environment setting, which causes a Warning.

Serverless Warning --------------------------------------

 A valid service attribute to satisfy the declaration 'self:custom.hoge.environment' could not be found.

That’s all.
I hope this helps.