Respect path prefix when matching paths

[kevinmcconnell]

There are a couple places where behviour is dependent on whether a request path matches a configured value: identifying incoming health check requests; and identifying paths for which metrics should not be tracked.

In both of these cases, if an app is deployed under a path prefix (and strips the prefix) then the expected behaviour is that we match that path against what the upstream sees. So we need to factor in any prefix-stripping before paths are matched.

[Copilot]

Pull request overview

This PR updates path-dependent behaviors (health check request detection, excluded-metrics path matching, and proxy path rewriting) to account for services deployed under a stripped path prefix, so comparisons are made against the upstream/target’s view of the request path.

Changes:

• Introduces RoutedTargetPath and uses it for health check matching, metrics exclusion matching, and reverse-proxy path rewriting when a matched prefix is stripped.
• Adds test coverage for health check and excluded-metrics behavior when a matched prefix is present and StripPrefix is enabled.
• Documents that excluded paths should be specified as the upstream receives them (i.e., un-prefixed when prefixes are stripped).

Tip

If you aren't ready for review, convert to a draft PR.
Click "Convert to draft" or run gh pr ready --undo.
Click "Ready for review" or run gh pr ready to reengage.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
README.md	Clarifies how to specify excluded paths when prefixes are stripped.
internal/server/testing.go	Adds a test helper to attach a matched-prefix routing context to requests.
internal/server/target.go	Uses routed/stripped target path for health-check detection and proxy rewriting.
internal/server/target_test.go	Adds assertions covering health check matching under a stripped prefix.
internal/server/service.go	Uses routed/stripped target path for metrics-exclusion matching.
internal/server/service_test.go	Adds assertions covering metrics exclusion under a stripped prefix.
internal/server/router.go	Adds RoutedTargetPath helper used across path-dependent decisions.
internal/server/router_test.go	Adds integration coverage for paused health checks with path prefixes.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[Copilot]

Pull request overview

Copilot reviewed 8 out of 8 changed files in this pull request and generated no new comments.