Add documentation on how to build the layer zip, testing using python

Joris Vandermeersch · Joris Vandermeersch · commit fca8d2764e2d · 2024-11-06T23:32:17.000+01:00
diff --git a/README.MD b/README.MD
@@ -3,24 +3,46 @@
 A [layer](https://aws.amazon.com/about-aws/whats-new/2018/11/aws-lambda-now-supports-custom-runtimes-and-layers/)
 for AWS Lambda that allows your functions to use `openssl` binaries.
 
-## Getting Started
+This repository contains the code needed to create an AWS Lambda Layer that
+adds the OpenSSL binary and related files to a Lambda container.
 
-You can add this layer to any Lambda function you want.
-`PATH` already includes `/opt/bin` in Lambda, which is where it will be mounted.
+This is useful because Lambda Runtimes based on Amazon Linux 2 and newer do not
+include this binary.
 
-Click on Layers and choose "Add a layer", and "Provide a layer version
-ARN" and enter the following ARN (replace `us-east-1` with the region of your Lambda):
+## How to build
 
+To build the zip, just run
 ```
-arn:aws:lambda:us-east-1:034541671702:layer:openssl-lambda:1
+cd src
+./build.sh
 ```
 
+Then, log in to AWS Console, navigate to Lambda, and find the Layers subsection
+in the sidebar.
+
+There you can create a new layer, fill in the required details, and upload the
+zip you just created. After finishing this process, the new layer is available
+to be used in you lambda functions!
+
+## Using a Lambda Layer
+
+You can add this layer to any Lambda function you want.
+`PATH` already includes `/opt/bin` in Lambda, which is where it will be mounted.
+
+In some Runtimes, you may still need to alter the `LD_LIBRARY_PATH` environment
+variable, prepending /opt/lib64 to override the .so files already present in
+the image.
+
+In AWS Lambda console, find your function, then scroll down to Layers and
+choose "Add a layer", then select your layer.
+
 ![Provide layer ARN](https://raw.githubusercontent.com/alexandredavi/openssl-lambda-layer/master/img/provide.PNG "Provide layer ARN screenshot")
 
 Then click Add, save your lambda and test it out!
 
 ![Referenced layers](https://raw.githubusercontent.com/alexandredavi/openssl-lambda-layer/master/img/referenced.PNG "Referenced layer ARN screenshot")
 
+
 ## Simple example on Node.js
 
 ```js
@@ -30,3 +52,13 @@ exports.handler = async(event) => {
   execSync(' openssl genrsa -out testCert.key 2048', { encoding: 'utf8', stdio: 'inherit' })
 }
 ```
+
+## Simple example on Python
+
+```python
+import os
+import subprocess
+
+def handler(event, context):
+    subprocess.run("openssl genrsa 2048", env={'PATH': os.environ['PATH']})
+```
