.

wcfs/wcfs.go

@@ -1353,26 +1353,40 @@ func (w *Watch) pin(ctx context.Context, blk int64, rev zodb.Tid) (err error) {
 // XXX called synchronously - only 1 setupWatch call at a time?
 func (wlink *WatchLink) setupWatch(ctx context.Context, foid zodb.Oid, at zodb.Tid) (err error) {
 	defer xerr.Contextf(&err, "setup watch f<%s> @%s", foid, at)
+	head := wlink.head
+	bfdir := head.bfdir
+
 	// XXX locking
 
 	// XXX at = zobd.InvalidTid - remove watch
 
 	// XXX if watch was already established - we need to update it
 	w := wlink.byfile[foid]
-	if w != nil {
-		panic("TODO")	// XXX update the watch
-	}
-
+	if w == nil {
 		// watch was not previously established - set it up anew
 		// XXX locking
-	head := wlink.head
-	bfdir := head.bfdir
 		f := bfdir.fileTab[foid]
 		if f == nil {
 			// by "invalidation protocol" watch is setup after data file was opened
 			return fmt.Errorf("file not yet known or is not a ZBigFile")
 		}
 
+		w = &Watch{
+			link:   wlink,
+			file:   f,
+			at:     at,
+			//pinned: make(SetI64),
+			pinned: make(map[int64]zodb.Tid),
+		}
+
+	}
+
+	// XXX check at >= w.at
+	if !(at >= w.at) {
+		panic("TODO")
+	}
+
+
 	headAt := head.zconn.At()
 
 	// XXX wait head.zconn.At() ≥ at
@@ -1382,14 +1396,6 @@ func (wlink *WatchLink) setupWatch(ctx context.Context, foid zodb.Oid, at zodb.T
 		return fmt.Errorf("at is too far away back from head/at (%s)", headAt)
 	}
 
-	w = &Watch{
-		link:   wlink,
-		file:   f,
-		at:     at,
-		//pinned: make(SetI64),
-		pinned: make(map[int64]zodb.Tid),
-	}
-
 	// TODO register w to f here early, so that READs going in parallel to
 	// us preparing and processing initial pins, also send pins for read
 	// blocks. If we don't, we can miss to send pin for a freshly read
@@ -1400,6 +1406,7 @@ func (wlink *WatchLink) setupWatch(ctx context.Context, foid zodb.Oid, at zodb.T
 	// XXX locking
 
 	// pin all tracked file blocks that were changed in (at, head] range
+	f := w.file
 	for _, δfile := range bfdir.δFtail.SliceByFileRev(f, at, headAt) {
 		for blk := range δfile.Blocks {
 			_, already := toPin[blk]

wcfs/wcfs_test.py

@@ -671,6 +671,7 @@ def watch(w, zf, at):   # XXX -> ?
 
     # send watch request and check that we receive pins for in-cache blocks
     # changed > at.
+    # XXX use timeout to detect wcfs replying less pins.
     ctx, cancel = context.with_cancel(context.background())
     wg = sync.WorkGroup(ctx)