How do you reference serverless outputs from one app or service to another?-CodePudding

I want to be able to reference outputs or function-level information (ARN or name) that is in one app/service, in another app/service using Serverless Framework. I am specifically interested in referencing a function's ARN, and if it changes for any reason, I am able to have a decoupled reference in the other service/app.

For example, I have this serverless.yml in App A:

org: myOrg
app: appA
service: serviceA

...
myFunction:
  handler: src/index.handler
  name: ${self:app}-${self:service}-myFunction-${sls:stage}
  events:
    - httpApi:
        method: 'POST'
        path: /my-path

I want to be able to use the ARN of myFunction in appA and serviceA, in appB and serviceB. Something like this:

org: myOrg
app: appB
service: serviceB

...
custom:
  myFunctionArn: ${app:A-service:A-myFunctionArn} # <- here I want to be able to reference the ARN of the other deployed service

CodePudding user response：

You can achieve this by using serverless's outputs and then reference that in the other Serverless App or Service.

Using your example, in appA, serviceA, do this:

org: myOrg
app: appA
service: serviceA

...
myFunction:
  handler: src/index.handler
  name: ${self:app}-${self:service}-myFunction-${sls:stage}
  events:
    - httpApi:
        method: 'POST'
        path: /my-path

outputs:
  myFunctionArn:
    'Fn::GetAtt': [MyFunctionLambdaFunction, Arn]

Note, you have to use CloudFormation's generated resource names (see this great StackOverflow answer here). CloudFormation always outputs lambda function names as {titleCasedFunctionName}LambdaFunction, so myFunction becomes MyFunctionLambdaFunction

Then, in appB, serviceB, you can reference the output by following ${output:appname:stagename:regionname:my-service.var-key} mentioned in the Serverless docs linked above. This makes your appB, serviceB serverless.yml as:

org: myOrg
app: appB
service: serviceB

...
custom:
  myFunctionArn: ${output:appA:${self:provider.stage}:${self:provider.region}:serviceA.myFunctionArn}

I added variables for stage and region assuming this is a multi-stage deployment, and assuming that it is in the same region. If it is in a different region, then change ${self:provider.region} to the region of appA/serviceA.