Add README for Lambda layer (#258)

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*Description of changes:*


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Author: wangzlei

lambda-layer/README.md

@@ -0,0 +1,49 @@
+# AWS Lambda Application Signals Support
+
+This package provides support for **Application Signals** in AWS Lambda environment.
+
+## Features
+
+- Supports Application Signals, including traces and metrics, for AWS Lambda Python Runtimes.
+- Automates the deployment process, including the creation of the Application Python Lambda Layer and a sample Lambda function.
+
+## Prerequisites
+
+Before you begin, make sure you have installed and configured the following tools:
+
+- [Docker](https://www.docker.com/get-started)
+- [Terraform](https://www.terraform.io/downloads)
+- [AWS CLI](https://aws.amazon.com/cli/) (to configure AWS credentials)
+
+### Configure AWS Credentials
+
+Ensure that your AWS credentials are properly configured in your local environment. You can use the following command with the AWS CLI:
+
+```bash
+aws configure
+```
+This will prompt you to enter your `AWS Access Key ID`, `AWS Secret Access Key`, `Default region name`, and `Default output format`.
+
+## Installation and Deployment
+
+### 1. Clone the Repository
+
+First, clone this repository to your local machine:
+
+```bash
+git clone https://github.com/yourusername/your-repo.git
+```
+
+### 2. Run the Build Script
+
+Navigate to the `lambda-layer` folder and run the `build.sh` script. This will create the Application Python Lambda Layer and a Lambda sample app in your AWS account:
+
+```bash
+cd lambda-layer
+./build.sh
+```
+
+## Lambda Sample App
+
+Once the script has successfully run, you will see the deployed Lambda sample app in your AWS account. You can trigger the 
+Lambda function and view the traces and metrics through the AWS CloudWatch Console.

lambda-layer/src/Dockerfile

@@ -1,6 +1,4 @@
-ARG runtime=python3.12
-
-FROM public.ecr.aws/sam/build-${runtime}
+FROM public.ecr.aws/sam/build-python3.12 AS python312
 
 ADD . /workspace
 
@@ -14,10 +12,20 @@ RUN mkdir -p /build && \
   python3 -m pip install aws-opentelemetry-distro/ -t /build/python && \
   mv otel_wrapper.py /build/python && \
   mv otel-instrument /build && \
+  python3 -m compileall /build/python && \
   chmod 755 /build/otel-instrument && \
-  rm -rf /build/python/boto* && \
-  rm -rf /build/python/urllib3* && \
-  cd /build && \
+  rm -rf /build/python/urllib3*
+
+
+FROM public.ecr.aws/sam/build-python3.11 AS python311
+
+WORKDIR /workspace
+
+COPY --from=python312 /build /build
+
+RUN python3 -m compileall /build/python
+
+RUN cd /build && \
   zip -r aws-opentelemetry-python-layer.zip otel-instrument python
 
 CMD ["cp", "/build/aws-opentelemetry-python-layer.zip", "/out/aws-opentelemetry-python-layer.zip"]

lambda-layer/src/otel-instrument

@@ -84,27 +84,13 @@ export PYTHONPATH="$LAMBDA_LAYER_PKGS_DIR:$PYTHONPATH";
 
 export PYTHONPATH="$LAMBDA_RUNTIME_DIR:$PYTHONPATH";
 
-# Configure OpenTelemetry Python with environment variables
-
-# - We leave `OTEL_EXPORTER_OTLP_TRACES_ENDPOINT` to its default. This is
-#   `http://localhost:4318/v1/traces` because we are using the HTTP exporter
-
-# - If OTEL_EXPORTER_OTLP_PROTOCOL is not set by user, the default exporting protocol is http/protobuf.
-if [ -z "${OTEL_EXPORTER_OTLP_PROTOCOL}" ]; then
-    export OTEL_EXPORTER_OTLP_PROTOCOL=http/protobuf
-fi
 
 # - Set the service name
 
 if [ -z "${OTEL_SERVICE_NAME}" ]; then
     export OTEL_SERVICE_NAME=$AWS_LAMBDA_FUNCTION_NAME;
 fi
 
-# - Set the propagators
-
-if [[ -z "$OTEL_PROPAGATORS" ]]; then
-  export OTEL_PROPAGATORS="tracecontext,baggage,xray"
-fi
 
 export LAMBDA_RESOURCE_ATTRIBUTES="cloud.region=$AWS_REGION,cloud.provider=aws,faas.name=$AWS_LAMBDA_FUNCTION_NAME,faas.version=$AWS_LAMBDA_FUNCTION_VERSION,faas.instance=$AWS_LAMBDA_LOG_STREAM_NAME,aws.log.group.names=$AWS_LAMBDA_LOG_GROUP_NAME";