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MDEV-7394 : Making slave_skip_errors writable at runtime when slave is stopped #4634

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MDEV-7394 : Making slave_skip_errors writable at runtime when slave is stopped #4634

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11 changes: 8 additions & 3 deletions mysql-test/main/variables-notembedded.result
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Original file line number Diff line number Diff line change
@@ -1,5 +1,6 @@
---- Init ----
set @my_slave_net_timeout =@@global.slave_net_timeout;
set @my_slave_skip_errors =@@global.slave_skip_errors;
---- Test ----
set global slave_net_timeout=100;
set global sql_slave_skip_counter=100;
Expand Down Expand Up @@ -144,9 +145,13 @@ SELECT @@global.slave_skip_errors;
@@global.slave_skip_errors
0,3,100,137,643,1752
SET @@session.slave_skip_errors= 7;
ERROR HY000: Variable 'slave_skip_errors' is a read only variable
SET @@global.slave_skip_errors= 7;
ERROR HY000: Variable 'slave_skip_errors' is a read only variable
ERROR HY000: Variable 'slave_skip_errors' is a GLOBAL variable and should be set with SET GLOBAL
SET @@global.slave_skip_errors= "7";
SELECT @@global.slave_skip_errors;
@@global.slave_skip_errors
7
SET @@global.slave_skip_errors= "OFF";
set GLOBAL slave_skip_errors = @my_slave_skip_errors;
#
# Bug #11766769 : 59959: SMALL VALUES OF --MAX-ALLOWED-PACKET
# ARE NOT BEING HONORED
Expand Down
9 changes: 6 additions & 3 deletions mysql-test/main/variables-notembedded.test
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Expand Up @@ -7,6 +7,7 @@ source include/not_embedded.inc;
--echo ---- Init ----
# Backup global variables so they can be restored at end of test.
set @my_slave_net_timeout =@@global.slave_net_timeout;
set @my_slave_skip_errors =@@global.slave_skip_errors;

--echo ---- Test ----
set global slave_net_timeout=100;
Expand Down Expand Up @@ -145,10 +146,12 @@ SHOW VARIABLES like 'slave_skip_errors';
--error ER_INCORRECT_GLOBAL_LOCAL_VAR
SELECT @@session.slave_skip_errors;
SELECT @@global.slave_skip_errors;
--error ER_INCORRECT_GLOBAL_LOCAL_VAR
--error ER_GLOBAL_VARIABLE
SET @@session.slave_skip_errors= 7;
--error ER_INCORRECT_GLOBAL_LOCAL_VAR
SET @@global.slave_skip_errors= 7;
SET @@global.slave_skip_errors= "7";
SELECT @@global.slave_skip_errors;
SET @@global.slave_skip_errors= "OFF";
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@grooverdan grooverdan Mar 17, 2026

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Is this testing an additional path? Or just a reset?

If its just a reset, omit.

Either way, put the last line set GLOBAL slave_skip_errors = @my_slave_skip_errors; here as its relevant to this test.

Could put the first set @my_slave_skip_errors =@@global.slave_skip_errors; just prior to this test block.

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@Mahmoud-kh1 Mahmoud-kh1 Mar 17, 2026

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no it's not reset , I am saving the initial values in the beginning of the test , and resting in the end, but I will move those this block of test as you suggested

set GLOBAL slave_skip_errors = @my_slave_skip_errors;
#

--echo #
Expand Down
62 changes: 62 additions & 0 deletions mysql-test/suite/rpl/r/slave_skip_errors_writable.result
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@@ -0,0 +1,62 @@
# MDEV-7394 test dynamic slave_skip_errors (writable when slaves stopped)
include/master-slave.inc
[connection master]
connection slave;
STOP SLAVE;
SET GLOBAL slave_skip_errors = "1062";
START SLAVE;
SELECT @@global.slave_skip_errors;
@@global.slave_skip_errors
1062
connection master;
CREATE TABLE t1 (id INT PRIMARY KEY);
include/sync_slave_sql_with_master.inc
connection slave;
INSERT INTO t1 VALUES (2);
connection master;
INSERT INTO t1 VALUES (2);
include/sync_slave_sql_with_master.inc
connection slave;
include/check_slave_is_running.inc
START SLAVE;
Warnings:
Note 1254 Slave is already running
include/wait_for_slave_to_start.inc
SET GLOBAL slave_skip_errors = "1062";
ERROR HY000: This operation cannot be performed as you have a running slave ''; run STOP SLAVE '' first
STOP SLAVE;
SET GLOBAL slave_skip_errors = "1050,1004,1104,1146";
START SLAVE;
# erros should be showed in sorted order
SELECT @@global.slave_skip_errors;
@@global.slave_skip_errors
1004,1050,1104,1146
SET GLOBAL slave_ddl_exec_mode = STRICT;
# test that mulitiple errors are set correctly
connection slave;
include/stop_slave.inc
CREATE TABLE t2 (id INT);
include/start_slave.inc
connection master;
CREATE TABLE t2 (id INT);
INSERT INTO t1 VALUES (4);
connection slave;
connection slave;
include/check_slave_is_running.inc
connection master;
INSERT INTO t1 VALUES (3);
include/sync_slave_sql_with_master.inc
connection slave;
SELECT COUNT(*) FROM t1 WHERE id=3;
COUNT(*)
1
STOP SLAVE;
SET GLOBAL slave_skip_errors = "OFF";
START SLAVE;
connection master;
DROP TABLE t1;
DROP TABLE t2;
include/sync_slave_sql_with_master.inc
connection slave;
SET GLOBAL slave_ddl_exec_mode = DEFAULT;
include/rpl_end.inc
69 changes: 69 additions & 0 deletions mysql-test/suite/rpl/t/slave_skip_errors_writable.test
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@@ -0,0 +1,69 @@
--echo # MDEV-7394 test dynamic slave_skip_errors (writable when slaves stopped)

--source include/master-slave.inc
connection slave;
STOP SLAVE;
SET GLOBAL slave_skip_errors = "1062";
START SLAVE;
SELECT @@global.slave_skip_errors;

connection master;
CREATE TABLE t1 (id INT PRIMARY KEY);
--source include/sync_slave_sql_with_master.inc

connection slave;
INSERT INTO t1 VALUES (2);

connection master;
INSERT INTO t1 VALUES (2);
--source include/sync_slave_sql_with_master.inc

connection slave;
source include/check_slave_is_running.inc;
START SLAVE;
--source include/wait_for_slave_to_start.inc
--error ER_SLAVE_MUST_STOP
SET GLOBAL slave_skip_errors = "1062";

STOP SLAVE;
SET GLOBAL slave_skip_errors = "1050,1004,1104,1146";
START SLAVE;

--echo # erros should be showed in sorted order
SELECT @@global.slave_skip_errors;

SET GLOBAL slave_ddl_exec_mode = STRICT;
--echo # test that mulitiple errors are set correctly

connection slave;
--source include/stop_slave.inc
CREATE TABLE t2 (id INT);
--source include/start_slave.inc

connection master;
CREATE TABLE t2 (id INT);
INSERT INTO t1 VALUES (4);
sync_slave_with_master;

connection slave;
source include/check_slave_is_running.inc;

connection master;
INSERT INTO t1 VALUES (3);
--source include/sync_slave_sql_with_master.inc

connection slave;
SELECT COUNT(*) FROM t1 WHERE id=3;

STOP SLAVE;
SET GLOBAL slave_skip_errors = "OFF";
START SLAVE;

connection master;
DROP TABLE t1;
DROP TABLE t2;
--source include/sync_slave_sql_with_master.inc
connection slave;
SET GLOBAL slave_ddl_exec_mode = DEFAULT;

--source include/rpl_end.inc
4 changes: 0 additions & 4 deletions mysql-test/suite/sys_vars/r/slave_skip_errors_basic.result
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Expand Up @@ -15,7 +15,3 @@ SLAVE_SKIP_ERRORS OFF
select * from information_schema.session_variables where variable_name='slave_skip_errors';
VARIABLE_NAME VARIABLE_VALUE
SLAVE_SKIP_ERRORS OFF
set global slave_skip_errors=1;
ERROR HY000: Variable 'slave_skip_errors' is a read only variable
set session slave_skip_errors=1;
ERROR HY000: Variable 'slave_skip_errors' is a read only variable
2 changes: 1 addition & 1 deletion mysql-test/suite/sys_vars/r/sysvars_server_notembedded.result
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Expand Up @@ -4350,7 +4350,7 @@ NUMERIC_MIN_VALUE NULL
NUMERIC_MAX_VALUE NULL
NUMERIC_BLOCK_SIZE NULL
ENUM_VALUE_LIST NULL
READ_ONLY YES
READ_ONLY NO
COMMAND_LINE_ARGUMENT REQUIRED
VARIABLE_NAME SLAVE_SQL_VERIFY_CHECKSUM
VARIABLE_SCOPE GLOBAL
Expand Down
7 changes: 0 additions & 7 deletions mysql-test/suite/sys_vars/t/slave_skip_errors_basic.test
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Expand Up @@ -10,10 +10,3 @@ show session variables like 'slave_skip_errors';
select * from information_schema.global_variables where variable_name='slave_skip_errors';
select * from information_schema.session_variables where variable_name='slave_skip_errors';

#
# show that it's read-only
#
--error ER_INCORRECT_GLOBAL_LOCAL_VAR
set global slave_skip_errors=1;
--error ER_INCORRECT_GLOBAL_LOCAL_VAR
set session slave_skip_errors=1;
55 changes: 35 additions & 20 deletions sql/slave.cc
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Expand Up @@ -152,7 +152,6 @@ static bool wait_for_relay_log_space(Relay_log_info* rli);
static bool io_slave_killed(Master_info* mi);
static bool sql_slave_killed(rpl_group_info *rgi);
static int init_slave_thread(THD*, Master_info *, SLAVE_THD_TYPE);
static void make_slave_skip_errors_printable(void);
static void make_slave_transaction_retry_errors_printable(void);
static int safe_connect(THD* thd, MYSQL* mysql, Master_info* mi);
static int safe_reconnect(THD*, MYSQL*, Master_info*, bool);
Expand Down Expand Up @@ -809,7 +808,7 @@ int init_recovery(Master_info* mi, const char** errmsg)
Convert slave skip errors bitmap into a printable string.
*/

static void make_slave_skip_errors_printable(void)
void make_slave_skip_errors_printable(void)
{
/*
To be safe, we want 10 characters of room in the buffer for a number
Expand All @@ -829,12 +828,14 @@ static void make_slave_skip_errors_printable(void)
{
/* purecov: begin tested */
memcpy(slave_skip_error_names, STRING_WITH_LEN("OFF"));
slave_skip_error_names[3]= '\0';
/* purecov: end */
}
else if (bitmap_is_set_all(&slave_error_mask))
{
/* purecov: begin tested */
memcpy(slave_skip_error_names, STRING_WITH_LEN("ALL"));
slave_skip_error_names[3]= '\0';
/* purecov: end */
}
else
Expand Down Expand Up @@ -866,33 +867,28 @@ static void make_slave_skip_errors_printable(void)
DBUG_VOID_RETURN;
}

/*
Init function to set up array for errors that should be skipped for slave

SYNOPSIS
init_slave_skip_errors()
arg List of errors numbers to skip, separated with ','

NOTES
Called from get_options() in mysqld.cc on start-up
*/

bool init_slave_skip_errors(const char* arg)
bool init_slave_skip_errors_bitmap(const char* arg)
{
const char *p;
DBUG_ENTER("init_slave_skip_errors");

if (!arg || !*arg) // No errors defined
goto end;

if (my_bitmap_init(&slave_error_mask,0,MAX_SLAVE_ERROR))
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DBUG_RETURN(1);

if (!use_slave_mask)
{
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)
/* empty */;
if (!system_charset_info->strnncoll((uchar*)arg,4,(const uchar*)"all",4))
{
if (strlen(arg) == 3 && !system_charset_info->strnncoll((uchar*)arg,3,(const uchar*)"all",3)) {
bitmap_set_all(&slave_error_mask);
bitmap_clear_bit(&slave_error_mask,ER_CONNECTION_KILLED);
sql_print_warning("Slave: ER_CONNECTION_KILLED (%d) is not allowed in "
Expand Down Expand Up @@ -923,10 +919,29 @@ bool init_slave_skip_errors(const char* arg)
}

end:
make_slave_skip_errors_printable();
DBUG_RETURN(0);
}
/*
Init function to set up array for errors that should be skipped for slave

SYNOPSIS
init_slave_skip_errors()
arg List of errors numbers to skip, separated with ','

NOTES
Called from get_options() in mysqld.cc on start-up
*/
bool init_slave_skip_errors(const char* arg)
{
DBUG_ENTER("init_slave_skip_errors");
if (init_slave_skip_errors_bitmap(arg))
{
DBUG_RETURN(1);
}
make_slave_skip_errors_printable();
DBUG_RETURN(0);

}
/**
Make printable version if slave_transaction_retry_errors
This is never empty as at least ER_LOCK_DEADLOCK and ER_LOCK_WAIT_TIMEOUT
Expand Down
4 changes: 4 additions & 0 deletions sql/slave.h
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Expand Up @@ -174,6 +174,10 @@ 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 init_slave_skip_errors_bitmap(const char* arg);
void make_slave_skip_errors_printable(void);
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,
Expand Down
49 changes: 47 additions & 2 deletions sql/sys_vars.cc
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Expand Up @@ -6212,12 +6212,57 @@ static Sys_var_multi_source_ulonglong Sys_max_relay_log_size(
VALID_RANGE(0, 1024L*1024*1024), DEFAULT(0), BLOCK_SIZE(IO_SIZE),
ON_UPDATE(update_max_relay_log_size));

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 err= false;
mysql_mutex_unlock(&LOCK_global_system_variables);
mysql_mutex_lock(&LOCK_active_mi);

if (give_error_if_slave_running(1))
{
my_error(ER_SLAVE_MUST_STOP, MYF(0));
err= true;
}
if (!err)
{
if (init_slave_skip_errors_bitmap(opt_slave_skip_errors))
{
my_error(ER_OUT_OF_RESOURCES, MYF(0));
err= true;
}
else
{
/*
* global_update() already ran my_memdup() on the user's string and stored
* the heap pointer in opt_slave_skip_errors with ALLOCATED set.
* We must call self->cleanup() after building the bitmap to free that
* heap allocation before make_slave_skip_errors_printable() overwrites
* opt_slave_skip_errors with the static slave_skip_error_names[] buffer.
* Without this, the heap pointer is lost (leak) and ALLOCATED stays set,
* causing a crash when cleanup() later tries to free the static buffer.
*/
self->cleanup();
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@bnestere bnestere Apr 27, 2026

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Please add a comment explaining why we need to manually call self->cleanup()

make_slave_skip_errors_printable();
}
}
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@bnestere bnestere Apr 27, 2026

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Many of the lines in this file have whitespace at the end. Please look at your changes with git show to see this, and remove lines with such whitespace.


mysql_mutex_unlock(&LOCK_active_mi);
mysql_mutex_lock(&LOCK_global_system_variables);
return err;
}
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(NULL), 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>
Expand Down
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