Bug + Patch (Intersync 0.9.5)

Peter and all,

After debugging for a while (really hard with 6+
processes talking to each other), I finally found
the problem I had identified in December.

In a few words:
  - send_kmlsize was not called from the right place
  - rc handling in IZO_UPC_PERMIT was confusing
    but may not have caused real problems

See bug & comments in patch for more info.
Note that I am not yet familiar with SourceForge cvs,
so I would prefer to leave it to more experience people
for now.

Hope this helps,

Francois Gagnon.


BUG:
-----------------------------------------------
I seem to have found a bug in intersync-0.9.5.
I understand what happens, and it seems that
the code did not account for this specific case.

Scenario:

- 1 server, 2 clients
- Start server, start client A, start client B
- Client A: mkdir a
- Client B: mkdir b
- Client A: Abort, reintegration failed (directory exists)

What happens is:

- When client A does "mkdir a",
  it builds a kml locally that the server fetches.
  Since client A did not fetch anything
  from server, last received on client A = 0

- When client B does "mkdir b",
  server tells client A to fetch kml from server.
  However, client A starts reintegration based
  on last received which is 0.
  It then replays "mkdir a, mkdir b" instead of
  just "mkdir b" because rec->lr_remote_offset = 0

  CDEBUG(D_KML, "remote kmlsize: %Lu, local kmlsize:
  %Lu, already: %d\n", kmlsize, rec->lr_remote_offset, already);


SOLUTION:
----------------


--- ../source/intersync-0.9.5/intersync/upcall.c        2002-09-26
15:23:26.000000000 -0400
+++ intersync/upcall.c  2003-01-27 18:57:50.000000000 -0500
@@ -298,18 +298,31 @@
                         break;  /* this dramatic enough? */
                 }

-                if (fset->fset_server == NULL) {
-                        /* If we're the server, tell the permit holder
what the
-                         * new local KML size is so that it knows to skip
KML
-                         * that was generated as a result of records that
were
-                         * reintegrated while it held the permit. */
-                        rc = is_run_job(is, CONTEXT_JOB_SEND_KMLSIZE,
NULL, rep,
-                                        NULL);
-                }
                 if (rc == 0) {
                         is_wait_for_kml(fset);
                         fset->fset_permit_holder = NULL;
                 }
+
+                if (fset->fset_server == NULL) {
+                       /* This could happen if the server is initiating
permit revocation,
+                        * but in most cases (maybe all cases today ?),
clients will initiate request.
+                        * Note that IZO_UPC_PERMIT is only invoked by the
entity
+                        * asking permit revocation. See also
IZO_UPC_REVOKE_PERMIT below.
+
+                         * If we're the server, tell the permit holder
what the
+                         * new local KML size is so that it knows to skip
KML
+                         * that was generated as a result of records that
were
+                         * reintegrated while it held the permit. */
+                        rc = is_run_job(is, CONTEXT_JOB_SEND_KMLSIZE,
NULL, rep,
+                                        NULL);
+                        if (rc == -ENOTCONN) {
+                                CERROR("Disconnected from old permit
holder, this client will probably have reintegration conflicts.\n");
+                        } else  if (rc) {
+                                /* FIXME */
+                                CERROR("Failed, not sure what to do ?\n");
+                        }
+                }
+
                 upc_reply(pfd, &upc, rc);
                 break;
         }
@@ -360,6 +373,19 @@
                         } else {
                                 fset->fset_permit_holder = NULL;
                         }
+
+                       /* We are the server, tell the permit holder what
the
+                        * new local KML size is so that it knows to skip
KML
+                        * that was generated as a result of records that
were
+                        * reintegrated while it held the permit. */
+                       rc = is_run_job(is, CONTEXT_JOB_SEND_KMLSIZE, NULL,
rep,NULL);
+                        if (rc == -ENOTCONN) {
+                                CERROR("Disconnected from old permit
holder, this client will probably have reintegration conflicts.\n");
+                        } else  if (rc) {
+                                /* FIXME */
+                                CERROR("Failed, not sure what to do ?\n");
+                        }
+
                 }

                 /* Get the peer of the new permit holder. */





Francois Gagnon
Equant, CS&N, Strategic Technology Planning
Heraklion, 1041 route des Dolines, BP347
06906 Sophia Antipolis, Cedex, France
Phone: +33-(0)4-92-96-6325 (7-223-6325)




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