MDEV-7394 Make slave_skip_errors dynamic

Make slave_skip_errors dynamic so it can be changed while the slave is stopped. Attempts to change it while the slave is running are rejected with a clear error.

Author: Mahmoud-kh1

mysql-test/suite/rpl/r/rpl_skip_error_dynamic.result

@@ -0,0 +1,29 @@
+# MDEV-7394  test dynamic slave_skip_error (writable when slaves stopped)
+include/master-slave.inc
+[connection master]
+connection slave;
+# should reduce error because slave is not stopped
+SET GLOBAL slave_skip_errors = "1062";
+ERROR HY000: This operation cannot be performed as you have a running slave ''; run STOP SLAVE '' first
+SELECT @@global.slave_skip_errors;
+@@global.slave_skip_errors
+NULL
+STOP SLAVE;
+# should work corerctly because slaves stopped
+SET GLOBAL slave_skip_errors = "1062"
+SELECT @@global.slave_skip_errors;
+@@global.slave_skip_errors
+NULL
+SET GLOBAL slave_skip_errors = "1050";
+SELECT @@global.slave_skip_errors;
+@@global.slave_skip_errors
+1050
+SET GLOBAL slave_skip_errors = "";
+SELECT @@global.slave_skip_errors;
+@@global.slave_skip_errors
+
+START SLAVE;
+# should reduce error because slave is not stopped
+SET GLOBAL slave_skip_errors = "1040";
+ERROR HY000: This operation cannot be performed as you have a running slave ''; run STOP SLAVE '' first
+include/rpl_end.inc

mysql-test/suite/rpl/t/rpl_skip_error_dynamic.test

@@ -0,0 +1,28 @@
+--echo # MDEV-7394  test dynamic slave_skip_error (writable when slaves stopped)
+
+--source include/master-slave.inc
+
+--connection slave
+
+--echo # should reduce error because slave is not stopped
+--error ER_SLAVE_MUST_STOP
+SET GLOBAL slave_skip_errors = "1062";
+SELECT @@global.slave_skip_errors;
+
+STOP SLAVE;
+echo # should work corerctly because slaves stopped
+SET GLOBAL slave_skip_errors = "1062";
+SELECT @@global.slave_skip_errors;
+
+SET GLOBAL slave_skip_errors = "1050";
+SELECT @@global.slave_skip_errors;
+
+SET GLOBAL slave_skip_errors = "";
+SELECT @@global.slave_skip_errors;
+
+START SLAVE;
+--echo # should reduce error because slave is not stopped
+--error ER_SLAVE_MUST_STOP
+SET GLOBAL slave_skip_errors = "1040";
+
+--source include/rpl_end.inc

sql/slave.cc

@@ -711,8 +711,8 @@ static void make_slave_skip_errors_printable(void)
   DBUG_ASSERT(sizeof(slave_skip_error_names) > MIN_ROOM);
   DBUG_ASSERT(MAX_SLAVE_ERROR <= 999999); // 6 digits
 
-  /* Make @@slave_skip_errors show the nice human-readable value.  */
-  opt_slave_skip_errors= slave_skip_error_names;
+  /* we should not touch opt_slave_skip_errors here. we just build the printable string only. */
+  (void) opt_slave_skip_errors;
 
   if (!use_slave_mask || bitmap_is_clear_all(&slave_error_mask))
   {
@@ -774,8 +774,15 @@ bool init_slave_skip_errors(const char* arg)
   if (!arg || !*arg)                            // No errors defined
     goto end;
 
-  if (my_bitmap_init(&slave_error_mask,0,MAX_SLAVE_ERROR))
-    DBUG_RETURN(1);
+  if (!slave_error_mask.bitmap)
+  {
+    if (my_bitmap_init(&slave_error_mask, 0, MAX_SLAVE_ERROR))
+      DBUG_RETURN(1);
+  }
+  else
+  {
+    bitmap_clear_all(&slave_error_mask);
+  }
 
   use_slave_mask= 1;
   for (;my_isspace(system_charset_info,*arg);++arg)
@@ -801,6 +808,43 @@ bool init_slave_skip_errors(const char* arg)
   DBUG_RETURN(0);
 }
 
+
+bool check_slave_skip_errors(sys_var *self, THD *thd, set_var *var)
+{
+  return give_error_if_slave_running(0);
+}
+
+
+bool update_slave_skip_errors(sys_var *self, THD *thd, enum_var_type type)
+{
+  bool res= false;
+  mysql_mutex_unlock(&LOCK_global_system_variables);
+  mysql_mutex_lock(&LOCK_active_mi);
+
+  if (active_mi->slave_running)
+  {
+    my_error(ER_SLAVE_MUST_STOP, MYF(0));
+    res= true;
+  }
+  else
+  {
+    if (use_slave_mask)
+      my_bitmap_free(&slave_error_mask);
+
+    use_slave_mask= 0;
+
+    if (init_slave_skip_errors(opt_slave_skip_errors))
+    {
+      my_error(ER_WRONG_VALUE_FOR_VAR, MYF(0), "slave_skip_errors", opt_slave_skip_errors);
+      res= true;
+    }
+  }
+
+  mysql_mutex_unlock(&LOCK_active_mi);
+  mysql_mutex_lock(&LOCK_global_system_variables);
+  return res;
+}
+
 /**
   Make printable version if slave_transaction_retry_errors
   This is never empty as at least ER_LOCK_DEADLOCK and ER_LOCK_WAIT_TIMEOUT

sql/slave.h

@@ -190,6 +190,8 @@ extern const char *relay_log_basename;
 int init_slave();
 int init_recovery(Master_info* mi, const char** errmsg);
 bool init_slave_skip_errors(const char* arg);
+bool check_slave_skip_errors(sys_var *self, THD *thd, set_var *var);
+bool update_slave_skip_errors(sys_var *self, THD *thd, enum_var_type type);
 bool init_slave_transaction_retry_errors(const char* arg);
 int register_slave_on_master(MYSQL* mysql);
 int terminate_slave_threads(Master_info* mi, int thread_mask,

sql/sys_vars.cc

@@ -6243,8 +6243,10 @@ static Sys_var_charptr Sys_slave_skip_errors(
        "slave_skip_errors", "Tells the slave thread to continue "
        "replication when a query event returns an error from the "
        "provided list",
-       READ_ONLY GLOBAL_VAR(opt_slave_skip_errors), CMD_LINE(REQUIRED_ARG),
-       DEFAULT(0));
+       GLOBAL_VAR(opt_slave_skip_errors), CMD_LINE(REQUIRED_ARG),
+       DEFAULT(0), NO_MUTEX_GUARD, NOT_IN_BINLOG,
+       ON_CHECK(check_slave_skip_errors),
+       ON_UPDATE(update_slave_skip_errors));
 
 static Sys_var_on_access_global<Sys_var_ulonglong,
                             PRIV_SET_SYSTEM_GLOBAL_VAR_READ_BINLOG_SPEED_LIMIT>