Release 0.5.1: auto-unexclude, merge excluded_host into auth DB0.5.1

- /metrics: auto-remove exclusion when records mtime > excluded_at so
  hosts that resume uploading unexclude themselves on next scrape
- Consolidate excluded_host table into the auth DB (goprecords-auth.db)
  instead of a separate file — removes -db daemon flag and GOPRECORDS_DB env
- README: add host exclusion section with kubectl exec examples

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

1 files changed, 57 insertions, 26 deletions

diff --git a/internal/daemon/metrics.go b/internal/daemon/metrics.go
index 192db77..21701db 100644
--- a/internal/daemon/metrics.go
+++ b/internal/daemon/metrics.go
@@ -35,7 +35,11 @@ func buildMetrics(ctx context.Context, statsDir, dbPath string) ([]byte, error)
 	if err != nil {
 		return nil, fmt.Errorf("list records: %w", err)
 	}
-	excluded, err := loadExcludedSet(ctx, dbPath)
+	db := openMetricsDB(ctx, dbPath)
+	if db != nil {
+		defer db.Close()
+	}
+	excluded, err := loadExcludedMap(ctx, db)
 	if err != nil {
 		return nil, fmt.Errorf("load excluded hosts: %w", err)
 	}
@@ -46,12 +50,63 @@ func buildMetrics(ctx context.Context, statsDir, dbPath string) ([]byte, error)
 		if err != nil {
 			continue
 		}
-		isExcluded := excluded[e.Host]
+		isExcluded := resolveExcluded(ctx, db, e.Host, mtime, excluded)
 		writeHostMetric(&sb, e.Host, mtime, isExcluded)
 	}
 	return []byte(sb.String()), nil
 }
 
+// openMetricsDB opens (and schema-initialises) the SQLite DB at dbPath.
+// Returns nil silently on empty path or any open/schema error so the metrics
+// endpoint degrades gracefully when no DB is configured.
+func openMetricsDB(ctx context.Context, dbPath string) *sql.DB {
+	if dbPath == "" {
+		return nil
+	}
+	db, err := storage.Open(ctx, dbPath)
+	if err != nil {
+		return nil
+	}
+	if err := storage.CreateSchema(ctx, db); err != nil {
+		db.Close()
+		return nil
+	}
+	return db
+}
+
+// loadExcludedMap returns a map of host→excluded_at for all excluded hosts.
+func loadExcludedMap(ctx context.Context, db *sql.DB) (map[string]int64, error) {
+	if db == nil {
+		return map[string]int64{}, nil
+	}
+	hosts, err := storage.LoadExcludedHosts(ctx, db)
+	if err != nil {
+		return nil, err
+	}
+	m := make(map[string]int64, len(hosts))
+	for _, h := range hosts {
+		m[h.Host] = h.ExcludedAt
+	}
+	return m, nil
+}
+
+// resolveExcluded returns true if the host is currently excluded.
+// If the records file mtime is newer than excluded_at the exclusion is
+// automatically lifted in the DB and the host is treated as active again.
+func resolveExcluded(ctx context.Context, db *sql.DB, host string, mtime int64, excluded map[string]int64) bool {
+	excludedAt, isExcluded := excluded[host]
+	if !isExcluded {
+		return false
+	}
+	if mtime > excludedAt {
+		if db != nil {
+			_ = storage.RemoveExcludedHost(ctx, db, host)
+		}
+		return false
+	}
+	return true
+}
+
 func writeMetricHeader(sb *strings.Builder) {
 	sb.WriteString("# HELP goprecords_host_records_last_update_timestamp_seconds Unix timestamp of the last records file update for each host.\n")
 	sb.WriteString("# TYPE goprecords_host_records_last_update_timestamp_seconds gauge\n")
@@ -74,27 +129,3 @@ func recordsMtime(statsDir, host string) (int64, error) {
 	}
 	return fi.ModTime().Unix(), nil
 }
-
-func loadExcludedSet(ctx context.Context, dbPath string) (map[string]bool, error) {
-	if dbPath == "" {
-		return map[string]bool{}, nil
-	}
-	db, err := storage.Open(ctx, dbPath)
-	if err != nil {
-		return map[string]bool{}, nil
-	}
-	defer db.Close()
-	return loadExcludedHosts(ctx, db)
-}
-
-func loadExcludedHosts(ctx context.Context, db *sql.DB) (map[string]bool, error) {
-	hosts, err := storage.LoadExcludedHosts(ctx, db)
-	if err != nil {
-		return nil, err
-	}
-	set := make(map[string]bool, len(hosts))
-	for _, h := range hosts {
-		set[h.Host] = true
-	}
-	return set, nil
-}