Merge pull request #174 from CloudBytes-Academy/article

ART: Lambda deps using Python Function

content/aws/50001000-cdk-fn-create-lambda.md

@@ -206,6 +206,8 @@ Or learn some advanced methods on how to create lambda functions:
 
 1. [Import an existing lambda function]({filename}50001010-cdk-fn-import-lambda.md)
 2. [Using lambda layers]({filename}50001020-cdk-fn-lambda_layers.md)
+3. [Using Lambda PythonFunction to create lambda functions]({filename}50001030-cdk-fn-lambda-python-deps.md)
+4. [Running Lambda using AWS provided Docker image]({filename}50001030-cdk-fn-lambda-aws-docker.md)
 
 
 

content/aws/50001030-cdk-fn-lambda-python-deps.md

@@ -0,0 +1,98 @@
+Title: Manage Python dependencies in AWS Lambda using AWS CDK
+Date: 2023-11-05
+Category: AWS Academy
+Series: AWS CDK
+series_index: 1030
+Tags: aws, cdk, python
+Author: Rehan Haider
+Summary: We look at how to package, install and manage Python dependencies in AWS Lambda using AWS CDK
+Keywords: lambda, cdk, docker, dependencies
+
+
+We looked at how we can [install Python packages beyond the ones available by default in AWS Lambda]({filename}50001020-cdk-fn-lambda_layers.md#create-a-lambda-layer-in-aws-cdk-using-python-to-handle-dependencies). 
+
+But I have always found it a bit cumbersome and unelegant to use Lambda layers to handle dependencies. Intead, I will show you an alternative way to handle Python dependencies in AWS Lambda using AWS CDK using an L2 construct called `PythonFunction`.
+
+This is not availble in the `aws_cdk.aws_lambda` module, so we will have to install it using pip:
+
+```bash
+pip install aws-cdk.aws-lambda-python-alpha
+```
+
+## Create a lambda function using PythonFunction
+
+```python
+# filename: cdk_app/lambda_stack.py
+from aws_cdk import (
+    Stack,
+)
+# 👇🏽 import the python_alpha module
+from aws_cdk import aws_lambda_python_alpha as _lambda
+
+from constructs import Construct
+
+
+class LambdaStack(Stack):
+    def __init__(self, scope: Construct, construct_id: str, **kwargs) -> None:
+        super().__init__(scope, construct_id, **kwargs)
+
+        # 👇🏽 create a python lambda function
+        my_lambda = _lambda.PythonFunction(
+            self,
+            id="MyLambda",
+            entry="cdk_app/lambda", # 👈🏽 Required
+            runtime=_lambda.Runtime.PYTHON_3_10, # 👈🏽 Required
+            index="index.py", # 👈🏽 Optional, defaults to index.py
+            handler="handler", # 👈🏽 Optional, defaults to handler
+        )
+```
+
+In the above code we use `PythonFunction` to define a lambda function. It takes the following parameters:
+
+1. `scope`: The scope of the construct. In our case, it is the `LambdaStack` class.
+2. `id`: The id of the construct. In our case, it is `MyLambda`, this will be used to refer to the function in CloudFormation templates
+3. `entry`: The path to the directory where the lambda function is located. In our case, it is `lambda`
+4. `index`: The name of the file that contains the lambda function. In our case, it is `index.py`
+5. `handler`: The name of the handler function. In our case, it is `handler`
+
+By default, the Construct will look for a `requirements.txt` file within the `entry` directory and install the dependencies listed in it. 
+
+Let's create the `cdk_app/lambda/index.py` file:
+
+```python
+# filename: cdk_app/lambda/index.py
+
+import requests
+
+def handler(event, context):
+    response = requests.get("https://jsonplaceholder.typicode.com/todos/1")
+    return {
+        "statusCode": 200,
+        "body": response.json()
+    }
+```
+
+We put a `requirements.txt` file in the same directory as our `index.py` file with the following contents:
+
+```text
+requests
+```
+
+Now let's create the `app.py` file:
+
+```python
+# filename: app.py
+
+import aws_cdk as cdk
+from cdk_app.lambda_stack import LambdaStack
+
+app = cdk.App()
+
+lambda_stack = LambdaStack(app, "LambdaStack")
+
+app.synth()
+```
+
+Run `cdk deploy` to deploy the stack. 
+
+Using this method, you just need to capture your dependencies in a `requirements.txt` file and the construct will take care of the rest.