Log in to your AWS account and navigate to Lambda. Create a new function with "Use a blueprint":
- Blueprint name: Python version of "Create a microservice that interacts with a DDB table"
- Function name:
weatherLookup - Execution role: Create a new role with basic Lambda permissions
- Lambda function code: Replace with the contents of function01.py in this repo
- API Gateway trigger > Intent: Create a new API
- API type: HTTP API
Once you're in the function editor, click the API Gateway box in the Function overview section. This will display the API endpoint URL for your function. Open this in a new tab and verify that you see "Hello, World!". If so, your Lambda function is working!
function01.py has a simple "Hello, World!" response and takes no input.
function02.py receives a URL query parameter called zip and
echoes it back in the response. Add this to your testing URL to try it:
?zip=78758.
function03.py ignores (for now) the zip parameter and
hardcodes a latitude/longitude. Then it uses that to call an open-source weather
API (Open-Meteo) to get the forecast high temperature
for today at that location.
Before we continue, we need to set up a DynamoDB table and give our Lambda function access to it.
Go to DynamoDB in your AWS Console and click Create table:
- Table name:
zipCodeToLatLong - Partition key:
zipCode - Table settings: Default settings
Now open up the table and click Explore table items. Click Create item and set
zipCode to 78758. Then click Add new attribute, select number, and set the
attribute name to latitude with a value of 30.2672. Add another number
attribute with name longitude and value -97.7431. Click Create item to save
it.
Now go back to Lambda and open up your weatherLookup function so we can use
this data there.
function04.py uses the zip parameter to look up the
latitude/longitude in the DynamoDB table and pass that to the Open-Meteo API.
If you get the following error, you need to grant access to the Lambda function to access DynamoDB:
An error occurred (AccessDeniedException) when calling the GetItem operation: User: arn:aws:sts::000000000000:assumed-role/weatherLookup-role-ryvomkio/weatherLookup is not authorized to perform: dynamodb:GetItem on resource: arn:aws:dynamodb:us-east-2:000000000000:table/zipCodeToLatLong because no identity-based policy allows the dynamodb:GetItem action
In the function editor, click the Configuration tab and select Permissions.
Click the link under Role name to open the role in a new tab. There, under the
Permissions > Permission policies section, click Add permissions > Attach
policies. Search for "dynamo", check the box next to AmazonDynamoDBFullAccess,
and click Add permissions.
Adding things to DynamoDB by hand is tedious. Let's write some code to do it!
Go to Lambda in your AWS Console and click Create function and choose "Author from scratch":
- Function name:
batchLoader - Runtime: Python (latest version)
- Change default execution role > Use an existing role and select the same role as your
weatherLookupfunction (this will allow the function to access DynamoDB)
batchloader.py is a separate Lambda function that loads a small set of ZIP code mappings into your DynamoDB table. Run it directly from the Lambda console (use the Test button) and then verify that the entries got added to your table.
After loading these entries, you can request weather for the following ZIP codes: 10001, 22202, 30354, 60606, 90210, and 94111. You can add any others you like either directly to the table or by editing this file.
If you need help troubleshooting or want to dive deeper into any of these topics, refer to the following:
- DynamoDB SDK for Python (Boto3)
- Open-Meteo API documentation (also includes a lat/long lookup tool)
- AWS CDK Workshop - Cloud Development Kit is an Infrastructure-as-Code framework. This workshop walks you through defining Lambda functons and DynamoDB tables as code, which you can modify and deploy to provision and modify AWS resources programmatically.