feat(pipeline): use stale snapshot when upstream fetch fails

При ошибке CDN/ASN/DoH ingest использует последний снимок префиксов
(или просроченный ASN-кэш), если EVOBGP_STALE_ON_UPSTREAM_ERROR не равен 0.

Co-authored-by: Cursor <[email protected]>

internal/pipeline/collect_stale.go

@@ -0,0 +1,86 @@
+package pipeline
+
+import (
+	"fmt"
+	"log"
+	"net/netip"
+	"os"
+	"strings"
+
+	"evobgp/internal/store"
+)
+
+// staleOnUpstreamError reports whether ingest should keep last-known prefixes when an upstream fetch fails.
+// Enabled by default; set EVOBGP_STALE_ON_UPSTREAM_ERROR=0 to restore fail-fast behavior.
+func staleOnUpstreamError() bool {
+	v := strings.TrimSpace(os.Getenv("EVOBGP_STALE_ON_UPSTREAM_ERROR"))
+	if v == "" || v == "1" || strings.EqualFold(v, "true") {
+		return true
+	}
+	return false
+}
+
+func logStaleUpstream(kind, detail string) {
+	log.Printf("pipeline: stale upstream fallback (%s): %s", kind, detail)
+}
+
+func staleASNPrefixes(st store.Backend, priorSnapshot []store.PrefixRow, asn int64) ([]store.PrefixRow, string, bool) {
+	sourceKey := fmt.Sprintf("as:%d", asn)
+	if cached := prefixRowsForSource(priorSnapshot, sourceKey); len(cached) > 0 {
+		return cached, "", true
+	}
+	if st == nil {
+		return nil, "", false
+	}
+	ent, ok, err := st.GetASNPrefixCache(asn)
+	if err != nil || !ok || ent == nil || len(ent.Prefixes) == 0 {
+		return nil, "", false
+	}
+	var rows []store.PrefixRow
+	for _, p := range ent.Prefixes {
+		pfx, perr := netip.ParsePrefix(strings.TrimSpace(p))
+		if perr != nil {
+			continue
+		}
+		rows = append(rows, store.PrefixRow{Prefix: pfx.Masked().String(), Source: sourceKey})
+	}
+	if len(rows) == 0 {
+		return nil, "", false
+	}
+	return rows, ent.Holder, true
+}
+
+func staleDomainPrefixes(priorSnapshot []store.PrefixRow, fqdn string) ([]store.PrefixRow, bool) {
+	sourceKey := "domain:" + strings.TrimSpace(fqdn)
+	cached := prefixRowsForSource(priorSnapshot, sourceKey)
+	return cached, len(cached) > 0
+}
+
+func staleCDNPrefixes(st store.Backend, tenantID, moduleID string, priorSnapshot []store.PrefixRow, sourceID string) ([]store.PrefixRow, bool) {
+	sourceKey := cdnSourceKey(sourceID)
+	cached := cachedCDNPrefixRows(st, tenantID, moduleID, priorSnapshot, sourceKey)
+	return cached, len(cached) > 0
+}
+
+// asnCacheExpired returns cached ASN prefixes even past TTL (for stale fallback only).
+func asnCacheExpired(st store.Backend, asn int64) ([]netip.Prefix, string, bool) {
+	if st == nil {
+		return nil, "", false
+	}
+	ent, ok, err := st.GetASNPrefixCache(asn)
+	if err != nil || !ok || ent == nil || len(ent.Prefixes) == 0 {
+		return nil, "", false
+	}
+	out := make([]netip.Prefix, 0, len(ent.Prefixes))
+	for _, p := range ent.Prefixes {
+		pfx, perr := netip.ParsePrefix(strings.TrimSpace(p))
+		if perr != nil {
+			continue
+		}
+		out = append(out, pfx.Masked())
+	}
+	if len(out) == 0 {
+		return nil, "", false
+	}
+	return out, ent.Holder, true
+}