Docker build occurs when instantiating my stack 😢 (aws_lambda_python_alpha.PythonFunction)

[anentropic]

I have a python cdk codebase

I added a aws_lambda_python_alpha.PythonFunction to my stack... now when I instantiate the stack containing that Lambda a docker build gets triggered

Surely this should happen at synth/deploy time and not import time?

a) it's annoyingly slow, e.g. my unit tests now do this docker build multiple times 😢
b) it's also noisy - it prints a bunch of output to stderr:

#0 building with "desktop-linux" instance using docker driver

#1 [internal] load .dockerignore
#1 transferring context: 2B done
#1 DONE 0.0s

#2 [internal] load build definition from Dockerfile
#2 transferring dockerfile: 1.35kB done
#2 DONE 0.0s

#3 [internal] load metadata for public.ecr.aws/sam/build-python3.11:latest
#3 DONE 1.2s

#4 [1/2] FROM public.ecr.aws/sam/build-python3.11@sha256:1468e6000e3d406ab5b32e82ba3358440faf75398eef30aa997e2c8e4ad85b07
#4 DONE 0.0s

#5 [2/2] RUN     python -m venv /usr/app/venv &&     mkdir /tmp/pip-cache &&     chmod -R 777 /tmp/pip-cache &&     pip install --upgrade pip &&     mkdir /tmp/poetry-cache &&     chmod -R 777 /tmp/poetry-cache &&     pip install pipenv==2022.4.8 poetry==1.5.1 &&     rm -rf /tmp/pip-cache/* /tmp/poetry-cache/*
#5 CACHED

#6 exporting to image
#6 exporting layers done
#6 writing image sha256:e1b922db4e93213d2e2d81648a4527a255153724fb3bee8c5d60b52414d89c12 done
#6 naming to docker.io/library/cdk-5b8c97dd7abcdda0315d77958a20f1916e747f40b6a90a6c535051e0b9a80308 done
#6 DONE 0.0s

What's Next?
  View a summary of image vulnerabilities and recommendations → docker scout quickview
Bundling asset Website-test/Database/DBInitializer/ResourceInitializer Lambda/Code/Stage...
WARNING: The requested image's platform (linux/amd64) does not match the detected host platform (linux/arm64/v8) and no specific platform was requested
sending incremental file list
index.py
requirements.txt
...
(then installs the pip requirements)

this occurs at the point in the code where the PythonFunction is instantiated

I have something like:

from collections.abc import Sequence
from typing import Any, cast

from aws_cdk import (
    Duration,
    Stack,
    aws_ec2 as ec2,
    aws_lambda_python_alpha as python_lambda,
    aws_lambda,
    aws_logs,
)

class Group(Construct):
    def __init__(
        self,
        scope: Construct,
        construct_id: str,
        vpc: ec2.IVpc,
        subnet_selection: ec2.SubnetSelection,
        lambda_context: dict[str, Any],
        lambda_security_groups: Sequence[ec2.ISecurityGroup],
        lambda_timeout: Duration,
        lambda_src_path: str,
        lambda_log_retention_days: aws_logs.RetentionDays,
        lambda_memory_size: int | None = None,
    ):
        stack = Stack.of(self)

        # docker build occurs here:
        fn = python_lambda.PythonFunction(
            self,
            "The Lambda",
            entry=lambda_src_path,
            runtime=aws_lambda.Runtime.PYTHON_3_11,
            layers=[
                aws_lambda.LayerVersion.from_layer_version_arn(
                    self,
                    "Powertools",
                    layer_version_arn=f"arn:aws:lambda:{stack.region}:017000801446:layer:AWSLambdaPowertoolsPythonV2-Arm64:46",
                ),
            ],
            memory_size=lambda_memory_size or 128,  # MB
            architecture=aws_lambda.Architecture.ARM_64,
            function_name=f"{construct_id}-{fn_name_suffix}",
            vpc=vpc,
            vpc_subnets=subnet_selection,
            security_groups=lambda_security_groups,
            timeout=lambda_timeout,
            log_retention=lambda_log_retention_days,
        )

Is this a bug? Have I done something wrong? Or it just works like that?

[anentropic]

created as issue #27991

[github-actions[bot]]

Hello! Reopening this discussion to make it searchable.