.

go/zodb/db.go

@@ -190,13 +190,13 @@ func (opt *ConnOptions) String() string {
 
 	s += ", "
 	if opt.NoSync {
-		s += "no"
+		s += "!"
 	}
 	s += "sync"
 
 	s += ", "
 	if opt.NoPool {
-		s += "no"
+		s += "!"
 	}
 	s += "pool"
 
@@ -286,11 +286,16 @@ type hwaiter struct {
 //
 // Must be called db.mu released.
 //
-// XXX -> waitHead?
+// XXX -> waitHead? needHead? waitHeadAfter? ensureAt?
 func (db *DB) headWait(ctx context.Context, at Tid) (err error) {
 	db.mu.Lock()
 
 	// XXX check if db is already down -> error even if at is under coverage?
+	// XXX under mu - ok?
+	// XXX err ctx
+	if ready(db.down) {
+		return db.downErr
+	}
 
 	if at <= db.δtail.Head() {
 		db.mu.Unlock()
@@ -343,12 +348,6 @@ func (db *DB) Open(ctx context.Context, opt *ConnOptions) (_ *Connection, err er
 		}
 	}()
 
-	// check db is already down/closed
-	// XXX -> headWait?
-	if ready(db.down) {
-		return nil, db.downErr
-	}
-
 	// find out db state we should open at
 	at := opt.At
 	if at == 0 {
@@ -357,6 +356,11 @@ func (db *DB) Open(ctx context.Context, opt *ConnOptions) (_ *Connection, err er
 			at = db.δtail.Head()
 			db.mu.Unlock()
 		} else {
+			// don't bother to sync to storage if db is down
+			if ready(db.down) {
+				return nil, db.downErr
+			}
+
 			// sync storage for lastTid
 			var err error
 
@@ -370,14 +374,13 @@ func (db *DB) Open(ctx context.Context, opt *ConnOptions) (_ *Connection, err er
 		}
 	}
 
-	// proceed to open(at)
-
 	// wait for db.Head ≥ at
 	err = db.headWait(ctx, at)
 	if err != nil {
 		return nil, err
 	}
 
+	// open(at)
 	conn := db.open(at, opt.NoPool)
 	conn.resync(ctx, at)
 	return conn, nil
@@ -462,13 +465,8 @@ func (conn *Connection) Resync(ctx context.Context, at Tid) error {
 
 	// XXX err ctx?	("resync @at -> @at")
 
-	db := conn.db
-
-	// XXX check db is already down/closed
-	// XXX or -> headWait?
-
 	// wait for db.Head ≥ at
-	err := db.headWait(ctx, at)
+	err := conn.db.headWait(ctx, at)
 	if err != nil {
 		return err
 	}
@@ -483,7 +481,6 @@ func (conn *Connection) Resync(ctx context.Context, at Tid) error {
 // Must be called with conn.db released.
 func (conn *Connection) resync(ctx context.Context, at Tid) {
 	txn := transaction.Current(ctx)
-
 	conn.resync1(at)
 
 	// upon exit, with all locks released, register conn to txn.
@@ -493,6 +490,8 @@ func (conn *Connection) resync(ctx context.Context, at Tid) {
 }
 
 // resync1 serves resync.
+//
+// it computes δ(conn.at, at) and invalidates objects ∈ δ in conn cache.
 func (conn *Connection) resync1(at Tid) {
 	if conn.txn != nil {
 		panic("Conn.resync: previous transaction is not yet complete")
@@ -551,7 +550,6 @@ func (conn *Connection) resync1(at Tid) {
 	if δall {
 		// XXX keep synced with LiveCache details
 		// XXX -> conn.cache.forEach?
-		//     or leave this wait till .Load() time?
 		for _, wobj := range conn.cache.objtab {
 			obj, _ := wobj.Get().(IPersistent)
 			if obj != nil {
@@ -575,8 +573,8 @@ func (conn *Connection) resync1(at Tid) {
 //
 // XXX recheck [atMin    or   (atMin	-- see "= δtail.Tail" in resync.
 //
-// if there is no such connection in the pool - nil is returned.
-// must be called with db.mu locked.
+// If there is no such connection in the pool - nil is returned.
+// Must be called with db.mu locked.
 func (db *DB) get(atMin, at Tid) *Connection {
 	l := len(db.pool)