Refs MW-252

- reverted from tracking donor servicing thread. With xtrabackup SST,
  xtrabackup thread will call FTWRL and node is desynced upfront
- Skipping desync in FTWRL if node is operating as donor

Author: sjaakola

sql/lock.cc

@@ -1071,7 +1071,7 @@ void Global_read_lock::unlock_global_read_lock(THD *thd)
 #ifdef WITH_WSREP
     wsrep_locked_seqno= WSREP_SEQNO_UNDEFINED;
     wsrep->resume(wsrep);
-    if (!wsrep_desync && !thd->wsrep_donor)
+    if (!wsrep_desync && !wsrep_node_is_donor())
     {
       int ret = wsrep->resync(wsrep);
       if (ret != WSREP_OK)
@@ -1141,13 +1141,13 @@ bool Global_read_lock::make_global_read_lock_block_commit(THD *thd)
      Donor servicing thread is an exception, it should pause provider but not desync,
      as it is already desynced in donor state
   */
-  if (!WSREP(thd) && !thd->wsrep_donor)
+  if (!WSREP(thd) && !wsrep_node_is_donor())
   {
     DBUG_RETURN(FALSE);
   }
 
   /* if already desynced or donor, avoid double desyncing */
-  if (wsrep_desync || thd->wsrep_donor)
+  if (wsrep_desync || wsrep_node_is_donor())
   {
     WSREP_DEBUG("desync set upfont, skipping implicit desync for FTWRL: %d",
                 wsrep_desync);

sql/sql_class.cc

@@ -1088,8 +1088,7 @@ THD::THD()
    wsrep_po_in_trans(FALSE),
    wsrep_apply_format(0),
    wsrep_apply_toi(false),
-   wsrep_skip_append_keys(false),
-   wsrep_donor(false)
+   wsrep_skip_append_keys(false)
 #endif
 {
   ulong tmp;

sql/sql_class.h

@@ -3880,7 +3880,6 @@ class THD :public Statement,
   bool                      wsrep_apply_toi; /* applier processing in TOI */
   bool                      wsrep_skip_append_keys;
   wsrep_gtid_t              wsrep_sync_wait_gtid;
-  my_bool                   wsrep_donor; /* true if thread is SST donor servicing */
   ulong                     wsrep_affected_rows;
 #endif /* WITH_WSREP */
 };

sql/wsrep_mysqld.cc

@@ -1587,3 +1587,8 @@ wsrep_grant_mdl_exception(MDL_context *requestor_ctx,
   }
   return ret;
 }
+
+bool wsrep_node_is_donor()
+{
+  return (WSREP_ON) ? (local_status.get() == 2) : false;
+}

sql/wsrep_mysqld.h

@@ -330,4 +330,5 @@ int wsrep_alter_event_query(THD *thd, uchar** buf, size_t* buf_len);
 void wsrep_init_sidno(const wsrep_uuid_t&);
 #endif /* GTID_SUPPORT */
 
+bool wsrep_node_is_donor();
 #endif /* WSREP_MYSQLD_H */

sql/wsrep_sst.cc

@@ -979,7 +979,6 @@ static void* sst_donor_thread (void* a)
 
   wsp::thd thd(FALSE); // we turn off wsrep_on for this THD so that it can
                        // operate with wsrep_ready == OFF
-  thd.ptr->wsrep_donor = true;
   wsp::process proc(arg->cmd, "r", arg->env);
 
   err= proc.error();