Bug 621008 - parsing purge RUV from changelog at startup fails

The purge RUV contains a single CSN per vector representing the
last change trimmed from the changelog from each master.  At
shutdown this RUV is flushed to the changelog to a special entry
and it's read and deleted from the changelog at startup.
_cl5ReadRUV() calls ruv_init_from_bervals() which uses
get_ruvelement_from_berval() on each berval that was read from the
changelog's purge RUV.

The problem is that get_ruvelement_from_berval() rejects any
vector that doesn't have two CSNs, a minimum and a maximum.  Thus,
a replica that starts up is always missing a purge vector until
the next time trimming occurs and the in-memory purge vector is
updated.  This can cause replication to continue when changes that
still need to be sent to a consumer have been trimmed from the
changelog.

This patch sets a dummy CSN in the purge RUV, which is parsed
correctly.  This will cause replication to halt instead of skipping
changes that have been trimmed from the changelog, which is the
proper thing to do.  Thanks to Ulf for contributing this patch!

ldap/servers/plugins/replication/cl5_api.c

@@ -33,6 +33,7 @@
  * 
  * Copyright (C) 2001 Sun Microsystems, Inc. Used by permission.
  * Copyright (C) 2005 Red Hat, Inc.
+ * Copyright (C) 2010 Hewlett-Packard Development Company, L.P.
  * All rights reserved.
  * END COPYRIGHT BLOCK **/
 
@@ -3425,6 +3426,13 @@ static int _cl5WriteRUV (CL5DBFile *file, PRBool purge)
 
 	if (purge)
 	{
+		/* Set the minimum CSN of each vector to a dummy CSN that contains
+		 * just a replica ID, e.g. 00000000000000010000.
+		 * The minimum CSN in a purge RUV is not used so the value doesn't
+		 * matter, but it needs to be set to something so that it can be
+		 * flushed to changelog at shutdown and parsed at startup with the
+		 * regular string-to-RUV parsing routines. */
+		ruv_insert_dummy_min_csn(file->purgeRUV);
 		key.data = _cl5GetHelperEntryKey (PURGE_RUV_TIME, csnStr);
 		rc = ruv_to_bervals(file->purgeRUV, &vals);
 	}

ldap/servers/plugins/replication/repl5_ruv.c

@@ -33,6 +33,7 @@
  * 
  * Copyright (C) 2001 Sun Microsystems, Inc. Used by permission.
  * Copyright (C) 2005 Red Hat, Inc.
+ * Copyright (C) 2010 Hewlett-Packard Development Company, L.P.
  * All rights reserved.
  * END COPYRIGHT BLOCK **/
 
@@ -1946,6 +1947,26 @@ ruv_force_csn_update (RUV *ruv, CSN *csn)
 	}	
 }
 
+/* This routine is used to iterate the elements in a RUV and set each vector's
++ * minimal CSN to a dummy with just the rid set, e.g. 00000000000000010000 */
+void
+ruv_insert_dummy_min_csn (RUV *ruv)
+{
+	RUVElement *r;
+	int cookie;
+
+	for (r = dl_get_first (ruv->elements, &cookie); r;
+		r = dl_get_next (ruv->elements, &cookie)) {
+		if (r->csn && !r->min_csn) {
+			CSN *dummycsn = csn_new();
+			csn_init(dummycsn);
+			csn_set_replicaid(dummycsn, csn_get_replicaid(r->csn));
+			r->min_csn = dummycsn;
+		}
+	}
+}
+
+
 #ifdef TESTING /* Some unit tests for code in this file */
 
 static void

ldap/servers/plugins/replication/repl5_ruv.h

@@ -33,6 +33,7 @@
  * 
  * Copyright (C) 2001 Sun Microsystems, Inc. Used by permission.
  * Copyright (C) 2005 Red Hat, Inc.
+ * Copyright (C) 2010 Hewlett-Packard Development Company, L.P.
  * All rights reserved.
  * END COPYRIGHT BLOCK **/
 
@@ -120,6 +121,7 @@ PRBool ruv_has_csns(const RUV *ruv);
 PRBool ruv_has_both_csns(const RUV *ruv);
 PRBool ruv_is_newer (Object *sruv, Object *cruv);
 void ruv_force_csn_update (RUV *ruv, CSN *csn);
+void ruv_insert_dummy_min_csn (RUV *ruv);
 #ifdef __cplusplus
 }
 #endif