.

wcfs/__init__.py

@@ -82,7 +82,9 @@ class WCFS(object):
 # maintain isolated database view while at the same time sharing most of data
 # cache in OS pagecache of /head/bigfile/*.
 #
+# Use WCFS.connect(at) to create Conn.
 # Use .mmap to create new Mappings.
+# Use .resync to resync Conn onto different database view.
 #
 # Conn logically mirrors ZODB.Connection .
 class Conn(object):
@@ -163,7 +165,6 @@ def close(wconn):
 
         wconn._filetab = None
 
-
 # _pinner receives pin messages from wcfs and adjusts wconn mappings.
 #
 # XXX must be running without GIL: access to wcfs mmaped memory could come from
@@ -227,7 +228,7 @@ def _pin1(wconn, req):
             if not (mmap.blk_start <= req.blk < mmap.blk_stop):
                 continue    # blk ∉ mmap
 
-            trace('\tremmapblk %d @%s' % (req.blk, h(req.at)))
+            trace('\tremmapblk %d @%s' % (req.blk, (h(req.at) if req.at else "head")))
             # FIXME check if virtmem did not mapped RW page into this block already
             mmap._remmapblk(req.blk, req.at)
             trace('\t-> remmaped')
@@ -239,6 +240,25 @@ def _pin1(wconn, req):
             f.pinned[req.blk] = req.at
 
 
+# resync resyncs connection onto different database view.
+# XXX place=?
+@func(Conn)
+def resync(wconn, at):
+    # XXX locking
+
+    for foid in wconn._filetab:
+        # XXX if file was has no mappings and was not used during whole prev
+        # cycle - forget and stop watching it
+        _ = wconn._wlink.sendReq(context.background(), b"watch %s @%s" % (h(foid), h(at)))
+        if _ != "ok":
+            # XXX unregister f from _filetab
+            # XXX vvv -> errctx?
+            raise RuntimeError("resync @%s -> @%s: f<%s>: %s" % (h(wconn.at), h(at), h(foid), _))
+
+    wconn.at = at
+
+
+
 # mmap creates file mapping representing file[blk_start +blk_len) data as of wconn.at database state.
 @func(Conn)
 def mmap(wconn, foid, blk_start, blk_len): # -> Mapping
@@ -261,7 +281,7 @@ def mmap(wconn, foid, blk_start, blk_len): # -> Mapping
             if _ != "ok":
                 # XXX unregister f from _filetab
                 # XXX vvv -> errctx?
-                raise RuntimeError("mmap f<%s>[%d +%d): %s" % (h(foid), blk_start, blk_len, _))
+                raise RuntimeError("@%s: mmap f<%s>[%d +%d): %s" % (h(wconn.at), h(foid), blk_start, blk_len, _))
 
         # XXX relock wconn -> f ?