SAM/Serverless/CodeBuild clarification

Question

I am hoping for some clarification around some terms I have been seeing on the web as it pertains to AWS and specifically lambdas. For starters, I would like the know how the commands sam build/deploy work versus setting up a CodeBuild job. Do I need a CodeBuild job to run those commands? What files specifically does the sam deploy command look for? Does it look for serverless.yml or template.yml or both? What is a sam.yml file or are they antiquated?

I have an app with a CodeBuild pipeline for a lambda, but I am expanding my repo to contain multiple lambdas and thinking about putting a serverless.yml file in each lambda directory, but I don't want to create a CodeBuild job and buildspec for each one. I assume sam deploy searches for all template.yml and serverless.yml files and constructs your stack as a whole (and updates only what needs to be updated?)

App is in Node if curious using API Gateway. Any insight would be appreciated.

Answer 1

I will try to give brief answers:

• What does sam deploy do : It will zip the code and create cloudformation yaml file into .aws-sam folder and run cloudformation deploy.
• Do we need CodeBuild to run same deploy : We still need some server to run sam deploy or build with node installed, which could be a local machine or remote server or a CodeBuild environment.
• Do we need multiple templates? All Lambdas can be created in single template. But there is limit of 150 resources in cloudformation. if we have too many functions and APIs in single template, we will easily hit that limit. Each api might get converted into multiple cloud-formation resources. ex: 1 lambda function can be iam roles, cloudwatch logs, api routes, methods, integration, event source, etc.
• Does sam deploy always looks for template.yaml By default yes, but can be easily overridden by passing --template-file sam deploy --template-file template-x.yml
• Only changed resources are updated? Cloudformation update-stack updates only the resources that are changed.