Refs codership/mysql-wsrep#113

Protecting non replicated FLUSH session from brute force aborts

sql/sql_class.cc

@@ -861,6 +861,7 @@ extern "C" const char *wsrep_thd_exec_mode_str(THD *thd)
   return 
     (!thd) ? "void" :
     (thd->wsrep_exec_mode == LOCAL_STATE)  ? "local"         :
+    (thd->wsrep_exec_mode == LOCAL_FLUSH)  ? "flush"         :
     (thd->wsrep_exec_mode == REPL_RECV)    ? "applier"       :
     (thd->wsrep_exec_mode == TOTAL_ORDER)  ? "total order"   : 
     (thd->wsrep_exec_mode == LOCAL_COMMIT) ? "local commit"  : "void";

sql/sql_parse.cc

@@ -4165,6 +4165,11 @@ case SQLCOM_PREPARE:
   }
 
   case SQLCOM_UNLOCK_TABLES:
+#ifdef WITH_WSREP
+    mysql_mutex_lock(&thd->LOCK_wsrep_thd);
+    if (thd->wsrep_exec_mode == LOCAL_FLUSH) thd->wsrep_exec_mode = LOCAL_STATE;
+    mysql_mutex_unlock(&thd->LOCK_wsrep_thd);
+#endif /* WITH_WSREP */
     /*
       It is critical for mysqldump --single-transaction --master-data that
       UNLOCK TABLES does not implicitely commit a connection which has only
@@ -4667,6 +4672,12 @@ case SQLCOM_PREPARE:
                              FALSE, UINT_MAX, FALSE))
         goto error;
 
+#ifdef WITH_WSREP
+      mysql_mutex_lock(&thd->LOCK_wsrep_thd);
+      thd->wsrep_exec_mode = LOCAL_FLUSH;
+      mysql_mutex_unlock(&thd->LOCK_wsrep_thd);
+#endif /* WITH_WSREP */
+
       if (flush_tables_with_read_lock(thd, all_tables))
         goto error;
 
@@ -4687,6 +4698,12 @@ case SQLCOM_PREPARE:
     {
       WSREP_TO_ISOLATION_BEGIN(WSREP_MYSQL_DB, NULL, NULL)
     }
+    else
+    {
+      mysql_mutex_lock(&thd->LOCK_wsrep_thd);
+      thd->wsrep_exec_mode = LOCAL_FLUSH;
+      mysql_mutex_unlock(&thd->LOCK_wsrep_thd);
+    }
 #endif /* WITH_WSREP*/
 
     /*

sql/wsrep_hton.cc

@@ -40,7 +40,7 @@ void wsrep_cleanup_transaction(THD *thd)
   thd->wsrep_ws_handle.trx_id= WSREP_UNDEFINED_TRX_ID;
   thd->wsrep_trx_meta.gtid= WSREP_GTID_UNDEFINED;
   thd->wsrep_trx_meta.depends_on= WSREP_SEQNO_UNDEFINED;
-  thd->wsrep_exec_mode= LOCAL_STATE;
+  if (thd->wsrep_exec_mode != LOCAL_FLUSH) thd->wsrep_exec_mode= LOCAL_STATE;
   return;
 }
 

sql/wsrep_mysqld.cc

@@ -1499,12 +1499,13 @@ wsrep_grant_mdl_exception(MDL_context *requestor_ctx,
       mysql_mutex_unlock(&granted_thd->LOCK_wsrep_thd);
       ret = TRUE;
     }
-    else if (granted_thd->lex->sql_command == SQLCOM_FLUSH)
+    else if (granted_thd->lex->sql_command == SQLCOM_FLUSH ||
+             granted_thd->wsrep_exec_mode == LOCAL_FLUSH)
     {
-      WSREP_DEBUG("mdl granted over FLUSH BF");
+      WSREP_DEBUG("BF thread waiting for FLUSH");
       ticket->wsrep_report(wsrep_debug);
       mysql_mutex_unlock(&granted_thd->LOCK_wsrep_thd);
-      ret = TRUE;
+      ret = FALSE;
     }
     else if (request_thd->lex->sql_command == SQLCOM_DROP_TABLE)
     {

sql/wsrep_mysqld.h

@@ -30,6 +30,8 @@ class THD;
 enum wsrep_exec_mode {
   /* Transaction processing before replication. */
   LOCAL_STATE,
+  /* Local flush. */
+  LOCAL_FLUSH,
   /* Slave thread applying write sets from other nodes or replaying thread. */
   REPL_RECV,
   /* Total-order-isolation mode */