Router

GOV.UK Router is an HTTP reverse proxy built on top of triemux. It loads a routing table into memory from a MongoDB database and:

• forwards requests to backend application servers according to the path in the request URL
• serves HTTP 301 and 302 redirects for moved content and short URLs
• serves 410 Gone responses for resources that no longer exist

The sister project router-api provides a read/write interface to the underlying database.

Technical documentation

Recommended reading: How to Write Go Code

Run the test suite

Checks run automatically on GitHub on PR and push. For faster feedback, you can run the tests locally.

The lint check uses golangci-lint, which you can install via Homebrew or your favourite package manager:

brew install golangci-lint

You can run all tests (some of which need Docker installed) by running:

make test

You can also run just the unit tests or just the integration tests, using the unit_tests and integration_tests targets. The unit tests don't need Docker.

The trie and triemux packages have unit tests. To run these on their own:

go test -bench=. ./trie ./triemux

The integration tests need Docker in order to run MongoDB. They are intended to cover Router's overall request handling, error reporting and performance.

You can use --ginkgo.focus <partial regex> to run a subset of the integration tests, for example:

go test ./integration_tests -v --ginkgo.focus 'redirect should preserve the query string'

Debug output

To see debug messages when running tests, set both the ROUTER_DEBUG and ROUTER_DEBUG_TESTS environment variables:

ROUTER_DEBUG=1 ROUTER_DEBUG_TESTS=1 make test

Update the dependencies

This project uses Go Modules to vendor its dependencies. To update the dependencies:

1. Update all the dependencies, including test dependencies, in your working copy:

   make update_deps

2. Check for any errors and commit.

   git commit -- go.{mod,sum} vendor

3. Run the Router test suite. If you need to fix a failing test, keep your changes in separate commits to the go get / go mod commit.

4. Run the tests for all dependencies:

   go test all

   • If there are failures, look into each one and determine whether it needs fixing.
   • If anything under vendor/ needs changing then either raise a PR with the upstream project or revert to a set of versions that work together. Only go get and go mod should touch files in vendor/.

5. Raise a PR.

Further documentation

• Data structure
• Original thinking behind the router
• Example of adding a metric using the Go prometheus client library

Team

GOV.UK Platform Engineering team looks after this repo. If you're inside GDS, you can find us in #govuk-platform-engineering or view our kanban board.

Licence

MIT License