zalando / skipper / 22872236893

78%

Build Type

push

github

Committed by web-flow

Commit Message

feature: expose invalid routes via support listener API (#3897)

Fixes #3488

### Context

Operators in multitenant ingress setups currently have no programmatic
way to discover which routes failed validation — the only option is
grepping logs for `"failed to process route"` messages. The `routeTable`
already tracks `invalidRoutes []*eskip.Route` alongside `validRoutes`,
but `Routing.ServeHTTP` unconditionally serves only the valid set.
Invalid routes are silently dropped from the routing table with no API
visibility into what broke or why.

### Approach

This extends the existing `/routes` handler with a `?invalid=true` query
parameter rather than adding a separate endpoint. The query param
approach follows @szuecs's guidance in the issue — invalid routes are a
filtered view of the same data, not a distinct resource, and this avoids
new mux registrations or a parallel `ServeHTTP` implementation.

The harder design decision was how to expose error messages (per
@AlexanderYastrebov's suggestion). The validation errors are computed in
`processRouteDefs` and `newMatcher` but were previously only sent to
metrics and discarded. Rather than adding an error field to
`eskip.Route` (a core type used across the entire codebase for parsing,
serialization, and matching), the errors are stored in a separate
`invalidRouteErrors map[string]string` on `routeTable` and merged into
the JSON response via a custom `MarshalJSON` on `InvalidRouteResponse`.

### Changes

- `processRouteDefs` returns a third value — error messages keyed by
route ID — collected from filter, predicate, backend, and matcher
validation failures
- `routeTable` gains an `invalidRouteErrors` field, populated from both
`processRouteDefs` and `newMatcher` error paths in `receiveRouteMatcher`
- `Routing.ServeHTTP` switches between `validRoutes` and `invalidRoutes`
based on the `invalid` query param; all existing behavior (pagination,
content negotiation, `X-Count`/`X-Timestamp` headers) works identica... (continued)

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