AWS Lambda is Unable to find app.handler (Custom Docker Image)

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I want to deploy machine learning related code on AWS Lambda function as Docker image. Base Images provided by AWS for Python, don't allow to install using apt-get command. So I created custom docker image for AWS Lambda. Below is the code of my Dockerfile.

ref: Create an image from an alternative base image

ARG FUNCTION_DIR="/function"

FROM python:3.7-buster as build-image

# Install aws-lambda-cpp build dependencies
RUN apt-get update && \
  apt-get install -y \
  g++ \
  make \
  cmake \
  unzip \
  libcurl4-openssl-dev

RUN apt-get install -y python-opencv

# Include global arg in this stage of the build
ARG FUNCTION_DIR
# Create function directory
RUN mkdir -p ${FUNCTION_DIR}

# Install the runtime interface client
RUN pip install \
        --target ${FUNCTION_DIR} \
        awslambdaric

FROM python:3.7-buster

ARG FUNCTION_DIR
# Set working directory to function root directory
WORKDIR ${FUNCTION_DIR}

# Copy in the build image dependencies
COPY --from=build-image ${FUNCTION_DIR} ${FUNCTION_DIR}

COPY requirements.txt /
#RUN pip install -r /requirements.txt

COPY .  /function
ENV AWS_LAMBDA_RUNTIME_API=python3.7
ENTRYPOINT [ "/usr/local/bin/python", "-m", "awslambdaric" ]
CMD [ "app.handler" ]

My Folder structure is as below:

aws_lambda (Folder)
- Dockerfile
- app.py
- function (Folder)
  - app.py
- requirements.txt

When I run docker image, it shows error as below:

[ERROR] [1614258613176] LAMBDA_RUNTIME Failed to get next invocation. No Response from endpoint
Traceback (most recent call last):
  File "/usr/local/lib/python3.7/runpy.py", line 193, in _run_module_as_main
    "__main__", mod_spec)
  File "/usr/local/lib/python3.7/runpy.py", line 85, in _run_code
    exec(code, run_globals)
  File "/function/awslambdaric/__main__.py", line 21, in <module>
    main(sys.argv)
  File "/function/awslambdaric/__main__.py", line 17, in main
    bootstrap.run(app_root, handler, lambda_runtime_api_addr)
  File "/function/awslambdaric/bootstrap.py", line 416, in run
    event_request = lambda_runtime_client.wait_next_invocation()
  File "/function/awslambdaric/lambda_runtime_client.py", line 76, in wait_next_invocation
    response_body, headers = runtime_client.next()
RuntimeError: Failed to get next
Executing 'app.handler' in function directory '/function'

It seems it is unable to find /function directory but it is already there.

aws-lambda docker amazon-web-services python-3.x
1 Answers

I've run into this thing recently and this is what works for me.

My dockerfile:

ARG FUNCTION_DIR="/opt/myapp"

FROM ubuntu:16.04

RUN apt update \
    && apt upgrade \
    && apt-get install -y software-properties-common python-software-properties \
    && apt-add-repository -y ppa:deadsnakes/ppa \
    && apt update \
    && apt-get install -y python3.6 python3.6-dev python3-pip

RUN python3.6 -m pip --no-cache-dir install awslambdaric
ADD https://github.com/aws/aws-lambda-runtime-interface-emulator/releases/latest/download/aws-lambda-rie /usr/bin/aws-lambda-rie

ARG FUNCTION_DIR
RUN mkdir -p ${FUNCTION_DIR}
WORKDIR /opt
ADD myapp myapp
COPY entry.sh /opt/myapp/entry.sh
RUN chmod 755 /usr/bin/aws-lambda-rie /opt/myapp/entry.sh
WORKDIR /tmp
ENTRYPOINT [ "/opt/myapp/entry.sh" ]
CMD [ "/opt/myapp/app.handler" ]

My entrypoint

#!/bin/sh

if [ -z "${AWS_LAMBDA_RUNTIME_API}" ]; then
    exec /usr/bin/aws-lambda-rie /usr/bin/python3.6 -m awslambdaric $1
else
    exec /usr/bin/python3.6 -m awslambdaric $1
fi

Then I built my image with:

docker build --rm -t myimage .

And tested locally running with:

docker run -p 9000:8080 --rm -it myimage:latest

In another terminal I run:

curl -XPOST "http://localhost:9000/2015-03-31/functions/function/invocations" -d '{"field1":"..", "field2":".."}'

Elaboration starts. My app.py contain a method handler, which parse the argument event and retrieve the fields (you can see them in the curl call), then starts the elaboration. I set my workdir in /tmp because it's the only read/write folder in AWS Lambda so I can put there some intermediate files of my elaboration.

user_42674390
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