.

bigfile/_file_zodb.pyx

@@ -101,7 +101,7 @@ cdef public class _ZBigFile(BigFile) [object _ZBigFile, type _ZBigFile_Type]:
             if zf.wfileh == nil:
                 zconn = zf.zself._p_jar
                 assert zconn is not None
-                # XXX locking? or rely on that ZODB objects for must be used from under 1 thread only?
+                # XXX locking? or rely on that ZODB objects for zconn must be used from under 1 thread only?
 
                 # join zconn to wconn; link to wconn from _ZBigFile
                 pywconn   = pywconnOf(zconn)
@@ -132,7 +132,34 @@ cdef wcfs.PyConn pywconnOf(zconn):
     wc    = pywcfs.join(zurl)
     wconn = wc.connect(zconn_at(zconn))
 
-    # XXX register zconn synchronizer to wconn.resync on zconn open
-    # XXX zconn goes away -> wconn close & free
     zconn._wcfs_wconn = wconn
+
+    # keep wconn view of the database in sync with zconn
+    zconn._wcfs_wconn_zsync = ZSync(zconn, wconn)
+
     return wconn
+
+
+# ZSync keeps wconn in sync with zconn.
+# XXX -> make generic and usefor _ZBigFileH too?
+# XXX naming?
+class ZSync:
+    # .zconn
+    # .wconn
+
+    def __init__(zsync, zconn, wconn):
+        print('ZSync %r %r' % (zconn, wconn))
+        assert zconn.open
+        zsync.zconn = zconn     # XXX -> weakref
+        zsync.wconn = wconn
+
+        # when connection will be reopened -> zsync.on_connection_open()
+        zconn.onOpenCallback(zsync)
+
+    # DB.open() pops .zconn from connection pool and "opens" for usage.
+    # -> resync .wconn to new database view of ZODB connection.
+    def on_connection_open(zsync):
+        print('ZSync.resync %r %r' % (zsync.zconn, zsync.wconn))
+        zsync.wconn.resync(zconn_at(zsync.zconn))
+
+    # TODO zconn dealloc -> wconn.close