Record poll failures as rows: the row is the failure state (#165)

backend/internal/latest/poller.go

@@ -287,6 +287,24 @@ const (
 	outcomeError
 	outcomeNotFound
 )
+// word returns the wire spelling this outcome stores in poll_failures — the
+// same strings the pass log's columns use (C1, issue #164). Success, refusal
+// and browser loss return "" so recordFailure's "no statement" case is one
+// return: a challenge or a lost sidecar is no evidence about any particular
+// Series (ADR-0016).
+func (o readOutcome) word() string {
+	switch o {
+	case outcomeNotFound:
+		return "not_found"
+	case outcomeNoChapter:
+		return "no_chapter"
+	case outcomeUnfetchable:
+		return "unfetchable"
+	case outcomeError:
+		return "errors"
+	}
+	return ""
+}
 
 // outcomeCounts are the six named outcome counts of one pass. A success
 // count is derived, never stored: checked minus the five named failures,
@@ -456,6 +474,7 @@ func (p *Poller) runLanePass(ctx context.Context, name string, paced bool) time.
 			}
 		}
 		outcome := p.checkOne(ctx, sr)
+		p.recordFailure(sr, outcome)
 		if outcome == outcomeUnreachable {
 			// The mid-loop browser loss writes an empty skip on purpose: the
 			// pass returns before the checked counter increments, so its row
@@ -613,6 +632,28 @@ func maxSeriesWait(due []store.Series, now time.Time, rest time.Duration) time.D
 	}
 	return oldest
 }
+// recordFailure keeps one Series' failure row in step with its read
+// (ADR-0016): a failure word is upserted, a successful read deletes the row,
+// and refused or unreachable issue no statement at all. Called for every
+// outcome from the pass loop, so the four failure words and the success path
+// share one write point, and a forced Poll that reads the page clears through
+// the ordinary success path — no branch of its own. Log a store failure and
+// carry on: this is best-effort, and no single bad Series may stall a Lane.
+func (p *Poller) recordFailure(sr store.Series, outcome readOutcome) {
+	if outcome == outcomeSuccess {
+		if err := p.Store.ClearSeriesFailure(sr.Site, sr.SeriesID); err != nil {
+			log.Printf("latest poll %q: clear failure: %v", sr.Key(), err)
+		}
+		return
+	}
+	word := outcome.word()
+	if word == "" {
+		return
+	}
+	if err := p.Store.RecordSeriesFailure(sr.Site, sr.SeriesID, word, p.Now().UnixMilli()); err != nil {
+		log.Printf("latest poll %q: record failure: %v", sr.Key(), err)
+	}
+}
 
 // checkOne re-checks one series. Every failure path here is "log and move on":
 // the poller is a best-effort enhancement, and no single bad series may stall a