'Using AWS SAM-CLI requires rebuild every time I update the code

I am using SAM CLI to develop an API Gateway Lambda proxy integration. According to the docs, I should be able to use sam local start-api to test my endpoint locally. The start-api command allows for "hot reloading" as described in the AWS SAM documentation. However, I am not seeing this behavior.

My template.yaml file looks like:

Resources:
  HelloWorldFunction:
    Type: AWS::Serverless::Function
    Properties:
      PackageType: Image
      Architectures:
        - x86_64
      Events:
        HelloWorld:
          Type: Api
          Properties:
            Path: /hello
            Method: get
    Metadata:
      Dockerfile: Dockerfile
      DockerContext: ./hello_world
      DockerTag: python3.9-v1

When I run:

> sam build && sam local start-api

I can see that the endpoint is working:

Mounting HelloWorldFunction at http://127.0.0.1:3000/hello
You can now browse to the above endpoints to invoke your functions. You do not need to restart/reload SAM CLI while working on your functions, changes will be reflected instantly/automatically.

However, when I make changes to the lambda_handler function inside of ./hello_world/app.py, the response to curl http://localhost:3000 remains the same. No hot reloading occurs.

The only solution I have found was to run sam build for each code change. This dramatically slows down development time -- because of some dependencies inside of requirements.txt, I have to wait 1-2 minutes for the build for each code change. I could just work on the file in the .aws-sam/build directory -- as suggested here -- but this seems like a bad solution because I would have to maintain two copies of the handler simultaneously.

aws-serverless aws-sam aws-sam-cli

Solution 1:^[1]

A great solution to this problem is here. Essentially run:

sam local start-api -t template.yaml --skip-pull-image

This got hot reloading working for me.

Solution 2:^[2]

According to https://github.com/aws/aws-sam-cli/issues/920 & https://github.com/aws/aws-sam-cli/issues/901, you are expected to have two consoles/terminals open. One where you run sam local start-api and leave it alone. And another where you run sam build repeatedly (whenever you need to update).

If you find this > slightly annoying,

Solution 3:^[3]

I used to find it quite annoying to be running two terminals and having to repeatedly build. Hence I ended up writing a boilerplate that bundles my source code and dependencies into a dist directory, runs sam local start-api in parallel, and watches for changes to update the dist directory.

Here's the repo: https://github.com/zishanneno/aws-typescript-lambda-boilerplate

Developing and debugging with this is much faster compared to building manually on every little code update.

Sources

This article follows the attribution requirements of Stack Overflow and is licensed under CC BY-SA 3.0.

Source: Stack Overflow

Solution	Source
Solution 1	Ian-B
Solution 2
Solution 3	Zishan Neno

'Using AWS SAM-CLI requires rebuild every time I update the code

Solution 1:[1]

Solution 2:[2]

Solution 3:[3]

Sources

Related Questions

Solution 1:^[1]

Solution 2:^[2]

Solution 3:^[3]