hvt-geolocation

A Serverless Node lambda (GeolocationFunction) for querying, sorting (nearest-first) and paginating ATFs based on a supplied postcode.

Requirements

• node v18.16.0
• Docker
• SAM CLI

Run Locally

1. Follow build steps in hvt-data to prepare local dataset
2. hvt-read-api must be running
3. npm i
4. cp .env.development .env
5. npm run build:dev
6. npm run start:dev
7. To ensure that the lambdas have been successfully served, run the following command in a separate terminal:
   • curl --request GET http://localhost:3008/<POSTCODE-HERE>?page=1&limit=5
   • the response should be in the following format: { "Items": [ <ATF-1>, <ATF-2>, ... ] }

Run and watch Locally

As steps above but instead of build:dev

• npm run watch:dev

and in a separate terminal, run

• npm run start:dev

Debug Locally (VS Code only)

1. Run lambdas in debug mode: npm run start:dev -- -d 5858
2. Add a breakpoint to the lambda being tested (src/handler/index.ts)
3. Run the debug config from VS Code that corresponds to lambda being tested (GeolocationFunction)
4. Send an HTTP request to the lambda's URI (curl --request GET http://localhost:3008/<POSTCODE-HERE>?page=1&limit=5)

Tests

• The Jest framework is used to run tests and collect code coverage
• To run the tests, run the following command within the root directory of the project: npm test
• Coverage results will be displayed on terminal and stored in the coverage directory
  • The coverage requirements can be set in jest.config.js

Build for Production

1. npm i
2. add environment variables to .env
3. npm run build:prod
4. Zip file can be found in ./dist/

Logging

By using a utility wrapper (src/utility/logger) surrounding console.log, the awsRequestId and a "correlation ID" is output with every debug/info/warn/error message.

For this pattern to work, every service/lambda must forward their correlation ID to subsequent services via a header e.g. X-Correlation-Id.

In practice, the first lambda invoked by an initial request will not have received the X-Correlation-Id header, so its correlationId gets defaulted to its lambdaRequestId. This correlationId should then be used when invoking subsequent lambdas via the X-Correlation-Id header. Every lambda called subsequently will then check for that X-Correlation-Id header and inject it into their logs.

This shows an example of what the log looks like from the first invoked lambda:

2020-09-10T17:03:04.891Z	5ff37fce-5ace-114c-9120-a1406cc8d11d	INFO	{"apiRequestId":"c6af9ac6-7b61-11e6-9a41-93e8deadbeef","correlationId":"5ff37fce-5ace-114c-9120-a1406cc8d11d","message":"Here's a gnarly info message from lambda 1 - notice how my correlationId has been set to my lambdaRequestId?"}

This shows an example of what the logs look like from the second invoked lambda (called via the first lambda):

2020-09-10T17:05:31.627Z	32ff455b-057d-1dd7-98b8-7034bf182dc8	INFO	{"apiRequestId":"d9222e0a-6bd9-49e0-84dd-ffe0680bd141","correlationId":"5ff37fce-5ace-114c-9120-a1406cc8d11d","message":"Here's a gnarly info message from lambda 2 - notice how my correlationId is the same as the lambda 1"}