MDEV-10161: wsrep_sync_wait not enabled when set to 1 in config file

Since wsrep_sync_wait & wsrep_causal_reads variables are related,
they are always kept in sync whenever one of them changes.
Same is tried on server start, where wsrep_sync_wait get updated
based on wsrep_causal_reads' value. But, since wsrep_causal_reads
is OFF by default, wsrep_sync_wait's value gets modified and loses
its WSREP_SYNC_WAIT_BEFORE_READ bit.

Fixed by syncing wsrep_sync_wait & wsrep_causal_reads values
individually on server start in mysqld_get_one_option() based
on command line arguments used.

mysql-test/suite/galera/galera_2nodes.cnf

@@ -9,7 +9,6 @@ default-storage-engine=innodb
 wsrep-provider=@ENV.WSREP_PROVIDER
 wsrep_node_address=127.0.0.1
 # enforce read-committed characteristics across the cluster
-wsrep-causal-reads=ON
 wsrep-sync-wait=7
 
 [mysqld.1]

mysql-test/suite/galera/r/galera_var_sync_wait.result

@@ -1,3 +1,12 @@
+#
+# MDEV-10161: wsrep_sync_wait not enabled when set to 1 in config file
+#
+SELECT @@global.wsrep_sync_wait;
+@@global.wsrep_sync_wait
+7
+SELECT @@global.wsrep_causal_reads;
+@@global.wsrep_causal_reads
+1
 CREATE TABLE t1 (f1 INT PRIMARY KEY) Engine=InnoDB;
 SET GLOBAL wsrep_sync_wait = 1;
 SHOW TABLES LIKE '%t1';

mysql-test/suite/galera/t/galera_var_sync_wait.test

@@ -5,6 +5,13 @@
 --source include/galera_cluster.inc
 --source include/have_innodb.inc
 
+--echo #
+--echo # MDEV-10161: wsrep_sync_wait not enabled when set to 1 in config file
+--echo #
+# galera_2nodes.cnf sets wsrep_sync_wait to 7
+SELECT @@global.wsrep_sync_wait;
+SELECT @@global.wsrep_causal_reads;
+
 --let $wsrep_sync_wait_orig = `SELECT @@wsrep_sync_wait`
 
 --connection node_1

sql/mysqld.cc

@@ -9266,6 +9266,16 @@ mysqld_get_one_option(int optid, const struct my_option *opt, char *argument)
 #endif
     break;
   }
+#ifdef WITH_WSREP
+  case OPT_WSREP_CAUSAL_READS:
+    wsrep_causal_reads_update(&global_system_variables);
+    break;
+  case OPT_WSREP_SYNC_WAIT:
+    global_system_variables.wsrep_causal_reads=
+      MY_TEST(global_system_variables.wsrep_sync_wait &
+              WSREP_SYNC_WAIT_BEFORE_READ);
+    break;
+#endif /* WITH_WSREP */
   }
   return 0;
 }

sql/mysqld.h

@@ -636,6 +636,10 @@ enum options_mysqld
   OPT_SSL_KEY,
   OPT_THREAD_CONCURRENCY,
   OPT_WANT_CORE,
+#ifdef WITH_WSREP
+  OPT_WSREP_CAUSAL_READS,
+  OPT_WSREP_SYNC_WAIT,
+#endif /* WITH_WSREP */
   OPT_MYSQL_COMPATIBILITY,
   OPT_MYSQL_TO_BE_IMPLEMENTED,
   OPT_which_is_always_the_last

sql/sys_vars.cc

@@ -4872,7 +4872,8 @@ static bool fix_wsrep_causal_reads(sys_var *self, THD* thd, enum_var_type var_ty
 static Sys_var_mybool Sys_wsrep_causal_reads(
        "wsrep_causal_reads", "Setting this variable is equivalent "
        "to setting wsrep_sync_wait READ flag",
-       SESSION_VAR(wsrep_causal_reads), CMD_LINE(OPT_ARG), DEFAULT(FALSE),
+       SESSION_VAR(wsrep_causal_reads),
+       CMD_LINE(OPT_ARG, OPT_WSREP_CAUSAL_READS), DEFAULT(FALSE),
        NO_MUTEX_GUARD, NOT_IN_BINLOG, ON_CHECK(0),
        ON_UPDATE(fix_wsrep_causal_reads),
        DEPRECATED("'@@wsrep_sync_wait=1'"));
@@ -4882,7 +4883,7 @@ static Sys_var_uint Sys_wsrep_sync_wait(
        "an operation of the type specified by bitmask: 1 - READ(includes "
        "SELECT, SHOW and BEGIN/START TRANSACTION); 2 - UPDATE and DELETE; 4 - "
        "INSERT and REPLACE",
-       SESSION_VAR(wsrep_sync_wait), CMD_LINE(OPT_ARG),
+       SESSION_VAR(wsrep_sync_wait), CMD_LINE(OPT_ARG, OPT_WSREP_SYNC_WAIT),
        VALID_RANGE(WSREP_SYNC_WAIT_NONE, WSREP_SYNC_WAIT_MAX),
        DEFAULT(WSREP_SYNC_WAIT_NONE), BLOCK_SIZE(1),
        NO_MUTEX_GUARD, NOT_IN_BINLOG, ON_CHECK(0),

sql/wsrep_mysqld.cc

@@ -561,8 +561,6 @@ int wsrep_init()
 
   wsrep_sst_auth_init(wsrep_sst_auth);
 
-  wsrep_causal_reads_update(&global_system_variables);
-
   wsrep_ready_set(FALSE);
   assert(wsrep_provider);