Ticket 47712 - betxn: retro changelog broken after cancelled transaction

Bug Description:  If a transaction is aborted (eg failing automember) and
			the retrocl is either broken (first txn after enabling rcl)
			or there are gaps in the changenumbers
			The reason that there are gaps in changenumbers is that
			if the txn is undone the entry is removed from the
			RCL database, but the last changnumer was incremented already
			The reason that the RCL seems to be broken is that
			the entry is removed from the database, but is still in
			the entry cache. For the first change the changenumber is
			always recreated and it detects the entry in the entrycache
			and returns "already exists". If the gaps would be avoided
			this would also happen for later failures.
Fix Description:   If the RCL postop function is called with an error set in the
			pblock, set a flag that next time a chnagenumber will be
			assigned it is recreated from the database.
		   It is not possible to remove the CL entry from the entry cache
			from the RCL plugin, cache functions are not available.
			The only solution is to avoid keeing RCL entries in the
			entry cache after their initial creation. Extend the
			operation flags to trigger a removal from cache in
			ldbm_back_add()

https://fedorahosted.org/389/ticket/47712

Reviewed by: richm, thanks

ldap/servers/plugins/retrocl/retrocl.h

@@ -159,6 +159,7 @@ extern void         retrocl_set_first_changenumber(changeNumber cn);
 extern changeNumber retrocl_get_last_changenumber(void);
 extern void         retrocl_commit_changenumber(void);
 extern void         retrocl_release_changenumber(void);
+extern void         retrocl_set_check_changenumber(void);
 extern changeNumber retrocl_assign_changenumber(void);
 extern int          retrocl_get_changenumbers(void);
 extern void         retrocl_forget_changenumbers(void);

ldap/servers/plugins/retrocl/retrocl_cn.c

@@ -45,6 +45,7 @@
 
 static changeNumber retrocl_internal_cn = 0;
 static changeNumber retrocl_first_cn = 0;
+static int check_last_changenumber = 0;
 
 /*
  * Function: a2changeNumber
@@ -408,15 +409,20 @@ changeNumber retrocl_assign_changenumber(void)
 
     slapi_rwlock_wrlock(retrocl_cn_lock);
 
-    if(retrocl_internal_cn <= retrocl_first_cn){ 
+    if((check_last_changenumber) || 
+	((retrocl_internal_cn <= retrocl_first_cn) &&
+	(retrocl_internal_cn > 1 ))){ 
         /* the numbers have become out of sync - retrocl_get_changenumbers
          * gets called only once during startup and it may have had a problem 
          * getting the last changenumber.         
          * If there was any problem then update the lastchangenumber from the changelog db.
          * This function is being called by only the thread that is actually writing
          * to the changelog.
+         *
+         * after the first change was applied both _cn numbers are 1, that's ok
          */                                                         
-        retrocl_update_lastchangenumber();                                   
+        retrocl_update_lastchangenumber(); 
+	check_last_changenumber = 0;                                  
     }                             
     retrocl_internal_cn++;
     cn = retrocl_internal_cn;
@@ -425,3 +431,10 @@ changeNumber retrocl_assign_changenumber(void)
 
     return cn;
 }
+
+void retrocl_set_check_changenumber(void)
+{
+	slapi_rwlock_wrlock(retrocl_cn_lock);
+	check_last_changenumber = 1;
+	slapi_rwlock_unlock(retrocl_cn_lock);
+}

ldap/servers/plugins/retrocl/retrocl_po.c

@@ -367,7 +367,8 @@ write_replog_db(
 	newPb = slapi_pblock_new ();
 	slapi_add_entry_internal_set_pb( newPb, e, NULL /* controls */, 
 					 g_plg_identity[PLUGIN_RETROCL], 
-					 0 /* actions */ );
+					/* dont leave entry in cache if main oparation is aborted */
+					 SLAPI_OP_FLAG_NEVER_CACHE);
 	slapi_add_internal_pb (newPb);
 	slapi_pblock_get( newPb, SLAPI_PLUGIN_INTOP_RESULT, &rc );
 	slapi_pblock_destroy(newPb);
@@ -607,6 +608,10 @@ int retrocl_postob (Slapi_PBlock *pb, int optype)
 
     if (rc != LDAP_SUCCESS) {
         LDAPDebug1Arg(LDAP_DEBUG_TRACE,"not applying change if op failed %d\n",rc);
+	/* this could also mean that the changenumber is no longer correct
+	 * set a flag to check at next assignment
+	 */
+	retrocl_set_check_changenumber();
         return SLAPI_PLUGIN_SUCCESS;
     }
 

ldap/servers/slapd/back-ldbm/ldbm_add.c

@@ -113,6 +113,7 @@ ldbm_back_add( Slapi_PBlock *pb )
 	int is_resurect_operation= 0;
 	int is_tombstone_operation= 0;
 	int is_fixup_operation= 0;
+	int is_remove_from_cache= 0;
 	int is_ruv = 0;				 /* True if the current entry is RUV */
 	CSN *opcsn = NULL;
 	entry_address addr = {0};
@@ -131,6 +132,7 @@ ldbm_back_add( Slapi_PBlock *pb )
 	is_tombstone_operation= operation_is_flag_set(operation,OP_FLAG_TOMBSTONE_ENTRY);
 	is_fixup_operation = operation_is_flag_set(operation, OP_FLAG_REPL_FIXUP);
 	is_ruv = operation_is_flag_set(operation, OP_FLAG_REPL_RUV);
+	is_remove_from_cache = operation_is_flag_set(operation, OP_FLAG_NEVER_CACHE);
 
 	inst = (ldbm_instance *) be->be_instance_info;
 	if (inst && inst->inst_ref_count) {
@@ -1166,6 +1168,8 @@ common_return:
 					}
 				}
 			}
+			if (is_remove_from_cache)
+				CACHE_REMOVE(&inst->inst_cache, addingentry);
 			CACHE_RETURN( &inst->inst_cache, &addingentry );
 		}
 		if (inst->inst_ref_count) {

ldap/servers/slapd/slapi-plugin.h

@@ -221,6 +221,7 @@ NSPR_API(PRUint32) PR_fprintf(struct PRFileDesc* fd, const char *fmt, ...)
 #define SLAPI_OP_FLAG_NEVER_CHAIN	0x000800 /* Do not chain the operation */
 #define SLAPI_OP_FLAG_NO_ACCESS_CHECK	0x10000 /* Do not check for access control - bypass them */
 #define SLAPI_OP_FLAG_BYPASS_REFERRALS	0x40000 /* Useful for performing internal operations on read-only replica */
+#define SLAPI_OP_FLAG_NEVER_CACHE	0x200000 /* added entry should not be kept in cache */
 
 #define SLAPI_OC_FLAG_REQUIRED	0x0001
 #define SLAPI_OC_FLAG_ALLOWED	0x0002

ldap/servers/slapd/slapi-private.h

@@ -442,6 +442,7 @@ char *slapi_filter_to_string_internal( const struct slapi_filter *f, char *buf,
 #define OP_FLAG_PAGED_RESULTS            0x040000 /* simple paged results */
 #define OP_FLAG_SERVER_SIDE_SORTING      0x080000 /* server side sorting  */
 #define OP_FLAG_REVERSE_CANDIDATE_ORDER  0x100000 /* reverse the search candidate list */
+#define OP_FLAG_NEVER_CACHE		 0x200000 /* never keep the entry in cache */
 
 /* reverse search states */
 #define REV_STARTED 1