DynamoDB API Lambda Function

A FastAPI-based Lambda function that provides a RESTful API interface to DynamoDB.

Setup and Deployment

Prerequisites

• Python 3.9
• AWS CLI configured with appropriate credentials
• A DynamoDB table named "Items" (or update the table name in the code)

Deployment Steps

1. Clone the repository

2. Install dependencies locally (if needed):

   pip install -r requirements_local.txt

3. Deploy to AWS Lambda:

   sh deploy.sh

The deploy script will:

• Create a clean package directory
• Install dependencies
• Package the Lambda function with dependencies
• Update the Lambda function code

IAM Permissions

The Lambda function needs permissions to access DynamoDB. Add this inline policy to your Lambda function's execution role:

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Action": [
        "dynamodb:GetItem",
        "dynamodb:PutItem",
        "dynamodb:DeleteItem",
        "dynamodb:Scan",
        "dynamodb:Query",
        "dynamodb:UpdateItem"
      ],
      "Resource": "arn:aws:dynamodb:*:*:table/Items"
    }
  ]
}

To add the policy:

1. Go to AWS Lambda console
2. Click on your function
3. Go to "Configuration" > "Permissions"
4. Click on the IAM role link
5. In IAM console, click "Add permissions" > "Create inline policy"
6. Switch to JSON editor and paste the policy above
7. Name it (e.g., "DynamoDBAccess") and create the policy

Testing

Test Events

The function can be tested using API Gateway v2 formatted test events. Here are examples for different operations:

GET All Items

{
  "version": "2.0",
  "routeKey": "GET /items",
  "rawPath": "/items",
  "rawQueryString": "",
  "headers": {
    "accept": "*/*",
    "content-length": "0",
    "host": "your-api-id.execute-api.region.amazonaws.com",
    "user-agent": "curl/7.64.1",
    "x-amzn-trace-id": "Root=1-5e6722a7-cc56xmpl46db7ae02d4da47dd",
    "x-forwarded-for": "1.2.3.4",
    "x-forwarded-port": "443",
    "x-forwarded-proto": "https"
  },
  "requestContext": {
    "accountId": "123456789012",
    "apiId": "api-id",
    "domainName": "your-api-id.execute-api.region.amazonaws.com",
    "domainPrefix": "your-api-id",
    "http": {
      "method": "GET",
      "path": "/items",
      "protocol": "HTTP/1.1",
      "sourceIp": "1.2.3.4",
      "userAgent": "curl/7.64.1"
    },
    "requestId": "JKJaXmPLvHcESHA=",
    "routeKey": "GET /items",
    "stage": "$default",
    "time": "10/Mar/2024:13:40:52 +0000",
    "timeEpoch": 1583856052000
  },
  "isBase64Encoded": false
}

POST New Item

{
  "version": "2.0",
  "routeKey": "POST /items",
  "rawPath": "/items",
  "rawQueryString": "",
  "headers": {
    "accept": "application/json",
    "content-type": "application/json",
    "content-length": "39",
    "host": "your-api-id.execute-api.region.amazonaws.com",
    "user-agent": "curl/7.64.1",
    "x-amzn-trace-id": "Root=1-5e6722a7-cc56xmpl46db7ae02d4da47dd",
    "x-forwarded-for": "1.2.3.4",
    "x-forwarded-port": "443",
    "x-forwarded-proto": "https"
  },
  "requestContext": {
    "accountId": "123456789012",
    "apiId": "api-id",
    "domainName": "your-api-id.execute-api.region.amazonaws.com",
    "domainPrefix": "your-api-id",
    "http": {
      "method": "POST",
      "path": "/items",
      "protocol": "HTTP/1.1",
      "sourceIp": "1.2.3.4",
      "userAgent": "curl/7.64.1"
    },
    "requestId": "JKJaXmPLvHcESHA=",
    "routeKey": "POST /items",
    "stage": "$default",
    "time": "10/Mar/2024:13:40:52 +0000",
    "timeEpoch": 1583856052000
  },
  "body": "{\"id\": \"test-item-1\", \"name\": \"Test Item\"}",
  "isBase64Encoded": false
}

To use these test events:

1. Go to AWS Lambda console
2. Select your function
3. Click the "Test" tab
4. Click "Create new event"
5. Give it a name (e.g., "GetItemsTest" or "CreateItemTest")
6. Paste the appropriate JSON
7. Click "Save" and "Test"

API Endpoints

The API supports both unversioned (default) and versioned endpoints. You can access the same functionality through either version:

Unversioned Endpoints (Default)

• GET /items - List all items
• GET /items/{item_id} - Get a specific item
• GET /items/{item_id}/{property_name} - Get a specific property of an item
• POST /items - Create a new item
• PUT /items/{item_id} - Update an item
• DELETE /items/{item_id} - Delete an item

V1 Endpoints

The v1 API introduces pagination for the items endpoint while maintaining the same functionality for other endpoints:

GET /v1/items (with pagination)

# Get first page
GET /v1/items?limit=5

Response:
{
    "items": [...],
    "next_cursor": "base64_encoded_cursor"
}

# Get next page using the cursor
GET /v1/items?limit=5&cursor=<next_cursor>

Response:
{
    "items": [...],
    "next_cursor": "base64_encoded_cursor_or_null"
}

Note: When next_cursor is null, there are no more items to retrieve.

Other v1 endpoints remain unchanged:

• GET /v1/items/{item_id} - Get a specific item
• GET /v1/items/{item_id}/{property_name} - Get a specific property of an item
• POST /v1/items - Create a new item
• PUT /v1/items/{item_id} - Update an item
• DELETE /v1/items/{item_id} - Delete an item

Note: In order for the API gateway to work, each of these routes (both unversioned and v1) needs to be added explicitly in the API Gateway console and attached to the Lambda function.

Logging

The function uses Loguru for logging, configured to:

• Write logs to CloudWatch
• Store rotating logs in /tmp/logs (Lambda's writable directory)
• Include timestamps, log levels, and detailed context

Dependencies

Key dependencies (see requirements.txt for versions):

• fastapi - Web framework
• pydantic - Data validation
• mangum - AWS Lambda/API Gateway integration
• boto3 - AWS SDK (included in Lambda runtime)