How do I specify a path in CMD in Dockerfile - docker

Question

I am trying to deploy an app in AWS Lambda. I am having issue accessing the handler that is deep inside the directory structure. Here is a simplified version of the issue.
My dir structure looks something like:
.
├── app.py
├── Dockerfile
├── events
│   ├── event.json
├── requirements.txt
├── template.yaml
And, here the contents of the files:
app.py
from fastapi import FastAPI
from mangum import Mangum
from pydantic import BaseModel
app = FastAPI(title='Serverless Lambda FastAPI', root_path="/Prod/")
class BodyModelAdd(BaseModel):
num1: int
num2: int
#app.post("/add", tags=["Add Two Numbers"])
def add(item: BodyModelAdd):
return {'result': {'num1': item.num1, 'num2': item.num2, 'sum': item.num1 + item.num2}}
handler = Mangum(app=app)
Dockerfile
FROM amazon/aws-lambda-python:3.9
COPY ./requirements.txt .
RUN pip3 install --no-cache-dir --upgrade -r requirements.txt --target "${LAMBDA_TASK_ROOT}"
COPY . ${LAMBDA_TASK_ROOT}
CMD ["app.handler"]
event.json
{
"body": "{\"num1\": 1, \"num2\": 2}",
"resource": "/add",
"path": "/add",
"httpMethod": "POST",
"requestContext": {
"path": "/add",
"resourcePath": "add",
"httpMethod": "POST"
}
}
requirements.txt
fastapi==0.85.1
uvicorn==0.19.0
mangum==0.16.0
pydantic==1.10.2
template.yaml
Note: I am very very new to Docker and AWS Lambda, and do not really have a good grasp of the contents of the yaml, but I grabbed this from a tutorial and it seems to work.
AWSTemplateFormatVersion: '2010-09-09'
Transform: AWS::Serverless-2016-10-31
Description: >
python3.9
Sample SAM Template for api_qna
Globals:
Function:
Timeout: 600
MemorySize: 1024
Resources:
PracticeFunction:
Type: AWS::Serverless::Function
Properties:
PackageType: Image
Architectures:
- x86_64
Events:
Root:
Type: Api
Properties:
Path: /
Method: ANY
NonRoot:
Type: Api
Properties:
Path: /{proxy+}
Method: ANY
Metadata:
Dockerfile: Dockerfile
DockerContext: ./
DockerTag: python3.9-v1
Outputs:
PracticeApi:
Description: "API Gateway endpoint URL for Prod stage"
Value: !Sub "https://${ServerlessRestApi}.execute-api.${AWS::Region}.amazonaws.com/Prod"
PracticeFunction:
Description: "Practice Tab Lambda Function ARN"
Value: !GetAtt PracticeFunction.Arn
PracticeFunctionIamRole:
Description: "Implicit IAM Role created"
Value: !GetAtt PracticeFunctionRole.Arn
To test it locally:
Once I have all these files, I first run sam build and then sam local invoke PracticeFunction --event events/event.json, and it gives the expected result as follows:
<some details deleted>
...
{"statusCode": 200, ..., "body": "{\"result\":{\"num1\":1,\"num2\":2,\"sum\":3}}", ...}%
So far so good. However, let me move the app.py to inside a dir as given below:
.
├── ... <-- app.py was here earlier
├── Dockerfile
├── events
│   ├── event.json
├── requirements.txt
├── src
│   ├── dir1
│      ├── __init__.py
│      ├── app.py <-- app.py moved here inside src/dir1/
├── template.yaml
The content of all the files are still the same (as given above). Now if I run sam build and then sam local invoke PracticeFunction --event events/event.json, it gives me an error as follows:
<some details deleted>
...
{"errorMessage": "Unable to import module 'app': No module named 'app'", "errorType": "Runtime.ImportModuleError", "requestId": "6cad0c02-73f4-4484-98fd-86c851d13548", "stackTrace": []}%
So it was expecting the app.py in the root dir and it could not find. Now my question is how do I handle this case when my app.py is not in the root project directory? Where do I specify the path to the app.py?
If I simply replace CMD ["app.handler"] with CMD ["./src/dir1/app.handler"] in the Dockerfile it gives an error saying {"errorMessage": "the 'package' argument is required to perform a relative import for '..src.dir1.app'", "errorType": "TypeError", .... I have also done some search but no luck yet (I must be missing something very trivial).
Sorry about the rather long post, but wanted to include all the details. Thank you so much for any help.