Add the plumbing that lets a checker receive (at evaluation, report
rendering, and metrics extraction) observations produced by other
checkers on DiscoveryEntry records it originally published.
Surface changes:
- RelatedObservation struct: one downstream observation, tagged with
the producing CheckerID and the Ref matching the DiscoveryEntry
it covers.
- ObservationGetter gains GetRelated(ctx, key), so rules can opt in
to cross-checker composition. mapObservationGetter (remote
/evaluate path) returns empty; the host owns lineage resolution.
- ReportContext interface: Data() + Related(key). Reporters consume
it instead of a raw json.RawMessage, which collapses the former
legacy/Ctx duplicate and gives one uniform signature:
GetHTMLReport(ctx ReportContext) (string, error)
ExtractMetrics(ctx ReportContext, t time.Time) ([]CheckMetric, error)
- NewReportContext(data, related) and StaticReportContext(data) build
fixed-payload contexts for entry points without an ObservationContext.
- ExternalReportRequest gains a Related map so the host can ship
pre-composed lineage to a remote checker over /report. The SDK's
/report handler threads it through to the reporter via
NewReportContext, closing the wire gap that previously forced
remote reports to a StaticReportContext with no related data.
Tests cover the Related map round-trip end-to-end via a peeking provider.
Introduce a DiscoveryEntry struct and an optional DiscoveryPublisher
interface that providers can co-implement to declare things worth
probing by other checkers (TLS endpoints, HTTP probes, ACME challenges,
DNSSEC keys, ...) without having to re-parse raw observations.
DiscoveryEntry carries an opaque Payload: the SDK does not interpret
it. Producers and consumers agree on the Payload schema through a
separate contract (eg. a small shared Go package imported by
both) identified by the free-form Type string. This keeps the SDK
free of protocol-specific concepts; new entry families can appear
without touching it.
The /collect HTTP handler type-asserts the provider against
DiscoveryPublisher immediately after Collect and forwards the
resulting entries in ExternalCollectResponse.Entries.
Adds HealthResponse carrying inflight count, total requests, 1/5/15-min
EWMA load averages, uptime, and NumCPU so a scheduler can pick the least
busy worker. A background sampler updates the load averages every 5s,
stopped by a new idempotent Close method. Work endpoints (/collect,
/evaluate, /report) are wrapped with a trackWork middleware; /health
and /definition are excluded so polling traffic does not pollute the
signal.
The previous implementation skipped empty fields, which meant targets
differing only in which fields were populated could produce the same
string (e.g. {UserId:"A"} and {DomainId:"A"} both gave "A"). This
caused key collisions when the string was used in storage index keys.
Keep Status as a plain integer on the wire so that OpenAPI/swaggo
can generate correct enum definitions without needing to handle
the custom string encoding. The String() method is preserved for
logging and debugging.
Make StatusUnknown the zero value (0) so an uninitialized CheckState
reads as "no signal yet" rather than as healthy. Push StatusOK and
StatusInfo to negative values so the natural int ordering matches
severity ordering: aggregators can simply take max() to compute the
worst status, and Unknown correctly sits above OK/Info but below Warn.
Status now (un)marshals as its string name ("OK", "WARN", ...) so the
wire format is stable across any future renumbering. UnmarshalJSON
still accepts raw ints for backward compatibility with older snapshots
and clients.
