API Gateway emulator

This is an experimental emulator for the API Gateway

The docker packaging in this repo will spin up a proxy listening on port 9000 which forwards requests to the URL pointed to by the GATEWAY_PROXY_DESTINATION_URL environment variable.

A proxy configuration UI is at port 9001.

Requests will be authenticated with a JWT. The issuer (iss), audience (aud) and authorised party (azp) claims of the JWT can be set via the GATEWAY_JWT_ISS, GATEWAY_JWT_AUD and GATEWAY_JWT_AZP environment variables. If not provided, they will default to http://localhost:9001/, https://audience.invalid/ and api-gateway@api-meta-2555105a.iam.gserviceaccount.com respectively.

The key id used to sign the JWTs can be set via GATEWAY_JWT_KEY_ID if necessary. If not provided, a random key id will be used.

A JSON document of the form {"[key id]": "[certificate]"} can be fetched from http://localhost:9001/certs. A standard JSON Web Key Set (JWKS) document can be fetched from http://localhost:9001/.well-known/jwks.json. Just enough of an OpenID discovery document to make the https://jwt.io/ debugger happy is available at http://localhost:9001/.well-known/openid-configuration. NOTE THE PORT NUMBER. THE CERTIFICATE AND JWKS DOCUMENTS ARE HOSTED FROM THE CONSOLE UI, NOT THE PROXY.

Initial proxy configuration can be influenced by other GATEWAY_... environment variables. See the definition of the Settings class.

Backend development

You can start a simple development instance via docker compose up --build. CHANGES ARE NOT HOT RELOADED. If you make a change, you will need to restart the server via docker compose down and docker compose up --build. The proxied application is a simple echo server which returns details of the incoming request as a JSON document.

The issuer for the JWT is set such that you should be able to copy the JWT passed to the backend and paste it into the https://jwt.io/ debugger and be able to validate the signature.

Backend development

Install pipx following the instructions on their site, then install the Python dependency manager and task runner:

$ pipx install poetry
$ pipx install poethepoet

The development environment can then be setup:

$ poetry install
$ poe setup

The pre-commit code checks (linting) should be performed automatically when committing to git (assuming poe setup has previously been run). To run the checks manually:

$ poe fix

Frontend development

You can install and start a development server as usual by running yarn install and yarn start in the frontend/ directory.

The application is available at http://localhost:3000/.

The development server automatically proxies API calls to http://localhost:9001/ so you can start an instance of the gateway emulator with default settings and it should Just Work (TM).