TODO.md

@@ -33,6 +33,10 @@ tested.
 
 # Completed Steps
 
+- 2026-10-26: a write to a stored AS, peering or peer keeps the earlier of the
+  two first-seen times and the later of the two last-seen times. An old update
+  from a collector catching up on a backlog no longer moves last seen back
+  (closes #162)
 - 2026-10-26: the status page shows "Route Churn/min", the number of prefix
   announcements and withdrawals, from all peers, in the last full clock minute.
   `/api/v1/stats` reports it as `route_churn_per_min` in `stream`, which

internal/database/database.go

@@ -945,6 +945,26 @@ func (d *Database) UpdatePrefixesBatch(prefixes map[string]time.Time) error {
 	return nil
 }
 
+// These statements update a stored AS, peering or peer. Each keeps the earlier
+// of the stored and the new first_seen, and the later of the stored and the new
+// last_seen. Some collectors send updates days old while they catch up on a
+// backlog. MIN and MAX compare the times as text, which is time order here: the
+// driver writes every time in one format, and every time is UTC.
+const (
+	updateASNSQL = `UPDATE asns
+		SET first_seen = MIN(first_seen, ?), last_seen = MAX(last_seen, ?)
+		WHERE asn = ?`
+
+	updatePeeringSQL = `UPDATE peerings
+		SET first_seen = MIN(first_seen, ?), last_seen = MAX(last_seen, ?)
+		WHERE as_a = ? AND as_b = ?`
+
+	updatePeerSQL = `UPDATE bgp_peers
+		SET peer_asn = ?, last_message_type = ?,
+		first_seen = MIN(first_seen, ?), last_seen = MAX(last_seen, ?)
+		WHERE peer_ip = ?`
+)
+
 // newASN returns a new ASN record first seen at seen.First and last seen at
 // seen.Last, with the handle and description from the AS info lookup when it
 // knows the number.
@@ -964,9 +984,8 @@ func newASN(number int, seen SeenTimes) ASN {
 	return asn
 }
 
-// upsertASN sets the last_seen time of ASN number to seen.Last with the given
-// statements, inserting the ASN when it is new. It reports whether it inserted
-// it.
+// upsertASN stores the seen times of ASN number with the given statements,
+// inserting the ASN when it is new. It reports whether it inserted it.
 func upsertASN(
 	ctx context.Context, selectStmt, updateStmt, insertStmt *sql.Stmt,
 	number int, seen SeenTimes,
@@ -979,8 +998,8 @@ func upsertASN(
 	err := selectStmt.QueryRowContext(ctx, number).Scan(&asn.ASN, &handle,
 		&description, &asn.FirstSeen, &asn.LastSeen)
 	if err == nil {
-		// ASN exists, update last_seen
-		_, err = updateStmt.ExecContext(ctx, seen.Last, number)
+		// ASN exists, update its seen times
+		_, err = updateStmt.ExecContext(ctx, seen.First, seen.Last, number)
 		if err != nil {
 			return false, fmt.Errorf("failed to update ASN %d: %w", number, err)
 		}
@@ -1030,8 +1049,7 @@ func (d *Database) GetOrCreateASNBatch(asns map[int]SeenTimes) error {
 	}
 	defer func() { _ = selectStmt.Close() }()
 
-	updateStmt, err := tx.PrepareContext(ctx,
-		"UPDATE asns SET last_seen = ? WHERE asn = ?")
+	updateStmt, err := tx.PrepareContext(ctx, updateASNSQL)
 	if err != nil {
 		return fmt.Errorf("failed to prepare update statement: %w", err)
 	}
@@ -1090,17 +1108,19 @@ func (d *Database) GetOrCreateASN(number int, timestamp time.Time) (*ASN, error)
 		"FROM asns WHERE asn = ?", number).
 		Scan(&asn.ASN, &handle, &description, &asn.FirstSeen, &asn.LastSeen)
 	if err == nil {
-		// ASN exists, update last_seen
+		// ASN exists, update its seen times
 		asn.Handle = handle.String
 		asn.Description = description.String
 
-		_, err = tx.Exec("UPDATE asns SET last_seen = ? WHERE asn = ?",
-			timestamp, number)
+		_, err = tx.Exec(updateASNSQL, timestamp, timestamp, number)
 		if err != nil {
 			return nil, err
 		}
 
-		asn.LastSeen = timestamp
+		// Return the seen times the update stored.
+		seen := SeenTimes{First: asn.FirstSeen, Last: asn.LastSeen}
+		seen.Add(timestamp)
+		asn.FirstSeen, asn.LastSeen = seen.First, seen.Last
 
 		err = tx.Commit()
 		if err != nil {
@@ -1259,9 +1279,7 @@ func (d *Database) RecordPeering(asA, asB int, seen SeenTimes) error {
 	}
 
 	if exists {
-		_, err = tx.Exec(
-			"UPDATE peerings SET last_seen = ? WHERE as_a = ? AND as_b = ?",
-			seen.Last, asA, asB)
+		_, err = tx.Exec(updatePeeringSQL, seen.First, seen.Last, asA, asB)
 	} else {
 		_, err = tx.Exec(`
 			INSERT INTO peerings (id, as_a, as_b, first_seen, last_seen)
@@ -1316,9 +1334,7 @@ func (d *Database) UpdatePeerBatch(peers map[string]PeerUpdate) error {
 	}
 	defer func() { _ = checkStmt.Close() }()
 
-	updateStmt, err := tx.PrepareContext(ctx,
-		"UPDATE bgp_peers SET peer_asn = ?, last_seen = ?, "+
-			"last_message_type = ? WHERE peer_ip = ?")
+	updateStmt, err := tx.PrepareContext(ctx, updatePeerSQL)
 	if err != nil {
 		return fmt.Errorf("failed to prepare update statement: %w", err)
 	}
@@ -1344,7 +1360,8 @@ func (d *Database) UpdatePeerBatch(peers map[string]PeerUpdate) error {
 
 		if exists {
 			_, err = updateStmt.ExecContext(ctx, update.PeerASN,
-				update.Seen.Last, update.MessageType, update.PeerIP)
+				update.MessageType, update.Seen.First, update.Seen.Last,
+				update.PeerIP)
 		} else {
 			_, err = insertStmt.ExecContext(ctx,
 				generateUUID().String(), update.PeerIP, update.PeerASN,
@@ -1393,11 +1410,8 @@ func (d *Database) UpdatePeer(
 	}
 
 	if exists {
-		_, err = tx.Exec(
-			"UPDATE bgp_peers SET peer_asn = ?, last_seen = ?, "+
-				"last_message_type = ? WHERE peer_ip = ?",
-			peerASN, timestamp, messageType, peerIP,
-		)
+		_, err = tx.Exec(updatePeerSQL,
+			peerASN, messageType, timestamp, timestamp, peerIP)
 	} else {
 		_, err = tx.Exec(
 			"INSERT INTO bgp_peers (id, peer_ip, peer_asn, first_seen, "+

internal/database/database_internal_test.go

@@ -20,6 +20,7 @@ import (
 
 	"git.eeqj.de/sneak/routewatch/internal/config"
 	"git.eeqj.de/sneak/routewatch/internal/logger"
+	"git.eeqj.de/sneak/routewatch/internal/ristypes"
 	"git.eeqj.de/sneak/routewatch/pkg/asinfo"
 	"github.com/mattn/go-sqlite3"
 )
@@ -1960,6 +1961,158 @@ func TestUpdatePeerBatchStoresTheEarliestAndLatestTimesOfANewPeer(
 	}
 }
 
+// backlogAge is how much older one write is than the other in the tests of
+// first_seen and last_seen, as when a collector catches up on a backlog.
+const backlogAge = 24 * time.Hour
+
+// batchSpan is how much earlier a batch's First is than its Last in the tests
+// of first_seen and last_seen.
+const batchSpan = time.Hour
+
+// TestWritesKeepEarliestFirstSeenAndLatestLastSeen writes a row of each of
+// asns, peerings and bgp_peers through each function that writes one, at a
+// newer time and at an older one. Each row takes the older write's First as
+// first_seen and the newer write's Last as last_seen. The test writes in both
+// orders, each in a database of its own. Newer then older is a collector
+// catching up on a backlog; older then newer is a feed that arrives in order.
+// Each function writes a row of its own. A batch write's First is batchSpan
+// before its Last, so the test catches the two swapped. A single-row write
+// takes one time.
+func TestWritesKeepEarliestFirstSeenAndLatestLastSeen(t *testing.T) {
+	t.Parallel()
+
+	const (
+		batchASN, singleASN = 64500, 64501
+		peerASN             = 64502
+		asnQuery            = "SELECT first_seen, last_seen FROM asns WHERE asn = ?"
+		peeringQuery        = "SELECT first_seen, last_seen FROM peerings " +
+			"WHERE as_a = ? AND as_b = ?"
+		peerQuery = "SELECT first_seen, last_seen FROM bgp_peers " +
+			"WHERE peer_ip = ?"
+	)
+
+	for name, olderFirst := range map[string]bool{
+		"newer then older": false,
+		"older then newer": true,
+	} {
+		t.Run(name, func(t *testing.T) {
+			t.Parallel()
+
+			db, err := New(&config.Config{StateDir: t.TempDir()}, logger.New())
+			if err != nil {
+				t.Fatalf("failed to create database: %v", err)
+			}
+			defer func() { _ = db.Close() }()
+
+			checkSeenTimes(t, db, olderFirst, func(seen SeenTimes) error {
+				return db.GetOrCreateASNBatch(map[int]SeenTimes{batchASN: seen})
+			}, batchSpan, asnQuery, batchASN)
+
+			checkSeenTimes(t, db, olderFirst, func(seen SeenTimes) error {
+				_, err := db.GetOrCreateASN(singleASN, seen.Last)
+
+				return err
+			}, 0, asnQuery, singleASN)
+
+			checkSeenTimes(t, db, olderFirst, func(seen SeenTimes) error {
+				return db.RecordPeering(batchASN, singleASN, seen)
+			}, batchSpan, peeringQuery, batchASN, singleASN)
+
+			checkSeenTimes(t, db, olderFirst, func(seen SeenTimes) error {
+				return db.UpdatePeerBatch(map[string]PeerUpdate{
+					testV4PeerIP: {
+						PeerIP: testV4PeerIP, PeerASN: peerASN,
+						MessageType: ristypes.MessageTypeUpdate,
+						Seen:        seen,
+					},
+				})
+			}, batchSpan, peerQuery, testV4PeerIP)
+
+			checkSeenTimes(t, db, olderFirst, func(seen SeenTimes) error {
+				return db.UpdatePeer(testPeerIP, peerASN,
+					ristypes.MessageTypeUpdate, seen.Last)
+			}, 0, peerQuery, testPeerIP)
+		})
+	}
+}
+
+// checkSeenTimes calls write twice, each time with First span before Last: at
+// newer times and at times backlogAge older. It writes the older times first
+// when olderFirst is true. It checks that query, given args, reads the older
+// write's First as first_seen and the newer write's Last as last_seen.
+func checkSeenTimes(
+	t *testing.T, db *Database, olderFirst bool,
+	write func(seen SeenTimes) error,
+	span time.Duration, query string, args ...any,
+) {
+	t.Helper()
+
+	newerLast := time.Date(2026, 1, 2, 3, 4, 5, 0, time.UTC)
+	newer := SeenTimes{First: newerLast.Add(-span), Last: newerLast}
+	older := SeenTimes{
+		First: newer.First.Add(-backlogAge),
+		Last:  newer.Last.Add(-backlogAge),
+	}
+
+	writes := []SeenTimes{newer, older}
+	if olderFirst {
+		writes = []SeenTimes{older, newer}
+	}
+
+	for _, seen := range writes {
+		err := write(seen)
+		if err != nil {
+			t.Fatalf("writing first %s, last %s: %v", seen.First, seen.Last, err)
+		}
+	}
+
+	var firstSeen, lastSeen time.Time
+
+	err := db.db.QueryRowContext(t.Context(), query, args...).
+		Scan(&firstSeen, &lastSeen)
+	if err != nil {
+		t.Fatalf("reading the row: %v", err)
+	}
+
+	if !firstSeen.Equal(older.First) || !lastSeen.Equal(newer.Last) {
+		t.Errorf("first seen %s, last seen %s; want %s, %s",
+			firstSeen, lastSeen, older.First, newer.Last)
+	}
+}
+
+// TestGetOrCreateASNReturnsStoredSeenTimes stores an AS at a newer time, then
+// at an older one. The second call returns the times the row now holds: the
+// older first_seen and the newer last_seen.
+func TestGetOrCreateASNReturnsStoredSeenTimes(t *testing.T) {
+	t.Parallel()
+
+	db, err := New(&config.Config{StateDir: t.TempDir()}, logger.New())
+	if err != nil {
+		t.Fatalf("failed to create database: %v", err)
+	}
+	defer func() { _ = db.Close() }()
+
+	const asn = 64500
+
+	newer := time.Date(2026, 1, 2, 3, 4, 5, 0, time.UTC)
+	older := newer.Add(-backlogAge)
+
+	_, err = db.GetOrCreateASN(asn, newer)
+	if err != nil {
+		t.Fatalf("GetOrCreateASN at %s: %v", newer, err)
+	}
+
+	got, err := db.GetOrCreateASN(asn, older)
+	if err != nil {
+		t.Fatalf("GetOrCreateASN at %s: %v", older, err)
+	}
+
+	if !got.FirstSeen.Equal(older) || !got.LastSeen.Equal(newer) {
+		t.Errorf("first seen %s, last seen %s; want %s, %s",
+			got.FirstSeen, got.LastSeen, older, newer)
+	}
+}
+
 // TestUpsertLiveRouteBatchWritesInKeyOrder writes new routes of two peers out
 // of key order, the last one a second announcement of the first, and checks
 // that the rows were inserted in key order, peer then prefix (each new row's id

internal/database/models.go

@@ -125,8 +125,8 @@ type LiveRouteDeletion struct {
 
 // SeenTimes is the earliest and the latest time one batch of updates saw an AS,
 // a peer or a peering. A row the batch adds is stored first seen at First and
-// last seen at Last; a row already stored keeps its first_seen and has its
-// last_seen set to Last.
+// last seen at Last. A row already stored takes First as its first_seen only
+// when First is earlier, and Last as its last_seen only when Last is later.
 type SeenTimes struct {
 	First time.Time
 	Last  time.Time