multi: migrate towers to use RangeIndex for AckedUpdates

In this commit, a migration is done that takes all the AckedUpdates of
all sessions and stores them in the RangeIndex pattern instead and
deletes the session's old AckedUpdates bucket. All the logic in the code
is also updates in order to write and read from this new structure.

watchtower/wtdb/client_db_test.go

@@ -221,6 +221,26 @@ func (h *clientDBHarness) fetchSessionCommittedUpdates(id *wtdb.SessionID,
 	return updates
 }
 
+func (h *clientDBHarness) isAcked(id *wtdb.SessionID, backupID *wtdb.BackupID,
+	expErr error) bool {
+
+	h.t.Helper()
+
+	isAcked, err := h.db.IsAcked(id, backupID)
+	require.ErrorIs(h.t, err, expErr)
+
+	return isAcked
+}
+
+func (h *clientDBHarness) numAcked(id *wtdb.SessionID, expErr error) uint64 {
+	h.t.Helper()
+
+	numAcked, err := h.db.NumAckedUpdates(id)
+	require.ErrorIs(h.t, err, expErr)
+
+	return numAcked
+}
+
 // testCreateClientSession asserts various conditions regarding the creation of
 // a new ClientSession. The test asserts:
 //   - client sessions can only be created if a session key index is reserved.
@@ -453,6 +473,7 @@ func testRemoveTower(h *clientDBHarness) {
 	}
 	h.insertSession(session, nil)
 	update := randCommittedUpdate(h.t, 1)
+	h.registerChan(update.BackupID.ChanID, nil, nil)
 	h.commitUpdate(&session.ID, update, nil)
 
 	// We should not be able to fully remove it from the database since
@@ -583,16 +604,6 @@ func testCommitUpdate(h *clientDBHarness) {
 	}, nil)
 }
 
-func perAckedUpdate(updates map[uint16]wtdb.BackupID) func(
-	_ *wtdb.ClientSession, seq uint16, id wtdb.BackupID) {
-
-	return func(_ *wtdb.ClientSession, seq uint16,
-		id wtdb.BackupID) {
-
-		updates[seq] = id
-	}
-}
-
 // testAckUpdate asserts the behavior of AckUpdate.
 func testAckUpdate(h *clientDBHarness) {
 	const blobType = blob.TypeAltruistCommit
@@ -628,6 +639,8 @@ func testAckUpdate(h *clientDBHarness) {
 
 	// Commit to a random update at seqnum 1.
 	update1 := randCommittedUpdate(h.t, 1)
+
+	h.registerChan(update1.BackupID.ChanID, nil, nil)
 	lastApplied := h.commitUpdate(&session.ID, update1, nil)
 	require.Zero(h.t, lastApplied)
 
@@ -654,6 +667,7 @@ func testAckUpdate(h *clientDBHarness) {
 	// value is 1, since this was what was provided in the last successful
 	// ack.
 	update2 := randCommittedUpdate(h.t, 2)
+	h.registerChan(update2.BackupID.ChanID, nil, nil)
 	lastApplied = h.commitUpdate(&session.ID, update2, nil)
 	require.EqualValues(h.t, 1, lastApplied)
 
@@ -681,13 +695,16 @@ func (h *clientDBHarness) assertUpdates(id wtdb.SessionID,
 	expectedPending []wtdb.CommittedUpdate,
 	expectedAcked map[uint16]wtdb.BackupID) {
 
-	ackedUpdates := make(map[uint16]wtdb.BackupID)
-	_ = h.listSessions(
-		nil, wtdb.WithPerAckedUpdate(perAckedUpdate(ackedUpdates)),
-	)
-	committedUpates := h.fetchSessionCommittedUpdates(&id, nil)
-	checkCommittedUpdates(h.t, committedUpates, expectedPending)
-	checkAckedUpdates(h.t, ackedUpdates, expectedAcked)
+	committedUpdates := h.fetchSessionCommittedUpdates(&id, nil)
+	checkCommittedUpdates(h.t, committedUpdates, expectedPending)
+
+	// Check acked updates.
+	numAcked := h.numAcked(&id, nil)
+	require.EqualValues(h.t, len(expectedAcked), numAcked)
+	for _, backupID := range expectedAcked {
+		isAcked := h.isAcked(&id, &backupID, nil)
+		require.True(h.t, isAcked)
+	}
 }
 
 // checkCommittedUpdates asserts that the CommittedUpdates on session match the
@@ -707,21 +724,6 @@ func checkCommittedUpdates(t *testing.T, actualUpdates,
 	require.Equal(t, expUpdates, actualUpdates)
 }
 
-// checkAckedUpdates asserts that the AckedUpdates on a session match the
-// expUpdates provided.
-func checkAckedUpdates(t *testing.T, actualUpdates,
-	expUpdates map[uint16]wtdb.BackupID) {
-
-	// We promote nil expUpdates to an initialized map since the database
-	// should never return a nil map. This promotion is done purely out of
-	// convenience for the testing framework.
-	if expUpdates == nil {
-		expUpdates = make(map[uint16]wtdb.BackupID)
-	}
-
-	require.Equal(t, expUpdates, actualUpdates)
-}
-
 // TestClientDB asserts the behavior of a fresh client db, a reopened client db,
 // and the mock implementation. This ensures that all databases function
 // identically, especially in the negative paths.