SHOW SLAVE STATUS gives wrong output with master-master and using SET uservars

Bug #860910 reported by Kenny Gryp
12
This bug affects 1 person
Affects Status Importance Assigned to Milestone
MariaDB
New
Undecided
Unassigned
MySQL Server
Unknown
Unknown
Percona Server moved to https://jira.percona.com/projects/PS
Fix Released
Undecided
Alexey Kopytov
5.1
Fix Released
Undecided
Alexey Kopytov
5.5
Fix Released
Undecided
Alexey Kopytov

Bug Description

Description:
In a master-master setup, a master can show a wrong 'SHOW SLAVE STATUS' output.

Requirements:
- master-master
- log_slave_updates

This is caused when using SET user-variables. and then using it to perform writes.
From then on the master that performed the insert will have a SHOW SLAVE STATUS that is
wrong and it will never update again until a write happens on the other master.

How to repeat:

### set up a masterA(serverid 1)<->masterB(serverid 2) with 2 way replication
### enable log-slave-updates on both databasegs
### execute on masterA:

create database test;
use test;
create table test3 (a int);
set @`test`:=0;
insert into test3 values (@test);

### To make it clearer, run the insert statement multiple times. You can even do any
other write you want! doesn't have to be related to test or use a variable.

### run 'show master status' on masterB
masterB> show master status;
+--------------------+----------+--------------+------------------+
| File | Position | Binlog_Do_DB | Binlog_Ignore_DB |
+--------------------+----------+--------------+------------------+
| masterB .000004 | 540 | | |
+--------------------+----------+--------------+------------------+

### run 'show slave status' on masterA
masterA> SHOW SLAVE STATUS\G
*************************** 1. row ***************************
Slave_IO_State: Waiting for master to send event
Master_Host: localhost
Master_User: r
Master_Port: 3309
Connect_Retry: 60
Master_Log_File: masterB.000004
Read_Master_Log_Pos: 540
Relay_Log_File: masterA-relay.000011
Relay_Log_Pos: 255
Relay_Master_Log_File: masterB.000004
Slave_IO_Running: Yes
Slave_SQL_Running: Yes
Replicate_Do_DB:
Replicate_Ignore_DB:
Replicate_Do_Table:
Replicate_Ignore_Table:
Replicate_Wild_Do_Table:
Replicate_Wild_Ignore_Table:
Last_Errno: 0
Last_Error:
Skip_Counter: 0
Exec_Master_Log_Pos: 313
Relay_Log_Space: 606
Until_Condition: None
Until_Log_File:
Until_Log_Pos: 0
Master_SSL_Allowed: No
Master_SSL_CA_File:
Master_SSL_CA_Path:
Master_SSL_Cert:
Master_SSL_Cipher:
Master_SSL_Key:
Seconds_Behind_Master: 0
Master_SSL_Verify_Server_Cert: No
Last_IO_Errno: 0
Last_IO_Error:
Last_SQL_Errno: 0
Last_SQL_Error:
Replicate_Ignore_Server_Ids:
Master_Server_Id: 1

==> masterA displays that it's waiting for master to send events on an old
exec_master_log_pos

### cat relay-log.info and master.info on masterA
Example:

$ cat masterA/master.info
18
masterB.000004
5261
localhost
r
r
3309
60

0.000

$ cat masterA/relay-log.info
./masterB-relay.000011
255
masterB.000004
313

$ stat masterA/relay-log.info
File: `2/relay-log.info'
Size: 54 Blocks: 8 IO Block: 4096 regular file
Device: 801h/2049d Inode: 796981 Links: 1
Access: (0660/-rw-rw----) Uid: ( 1000/ gryp) Gid: ( 1000/ gryp)
Access: 2011-09-27 16:59:45.863435966 +0200
Modify: 2011-09-27 16:53:06.874040990 +0200
Change: 2011-09-27 16:53:06.874040990 +0200

$ stat masterA/master.info
File: `2/master.info'
Size: 67 Blocks: 8 IO Block: 4096 regular file
Device: 801h/2049d Inode: 796979 Links: 1
Access: (0660/-rw-rw----) Uid: ( 1000/ gryp) Gid: ( 1000/ gryp)
Access: 2011-09-27 16:59:44.222616027 +0200
Modify: 2011-09-27 16:58:06.323690973 +0200
Change: 2011-09-27 16:58:06.323690973 +0200

==> masterA it's relay-log.info file is not updated anymore but master.info is.

### select * from test.test3 and you can see that all writes will be in there.

masterA> select * from test3;
+------+
| a |
+------+
| 0 |
+------+
1 row in set (0.00 sec)

### Actually the relay log should be empty as it should filter out it's own writes, but
the SET commands are in there, with the masterB serverid: 1
#110927 16:53:06 server id 1 end_log_pos 418 User_var
SET @`test`:=0/*!*/;

### The binary log of masterB will contain something like this,you can see that the SET
commands have changed to it's own serverid:
DROP TABLE IF EXISTS `test3` /* generated by server */
/*!*/;
# at 224
#110927 16:53:06 server id 2 end_log_pos 313 Query thread_id=3 exec_time=0 error_code=0
SET TIMESTAMP=1317135186/*!*/;
create table test3 (a int)
/*!*/;
# at 313
#110927 16:53:06 server id 2 end_log_pos 372 Query thread_id=3 exec_time=0 error_code=0
SET TIMESTAMP=1317135186/*!*/;
BEGIN
/*!*/;
# at 372
#110927 16:53:06 server id 1 end_log_pos 418 User_var
SET @`test`:=0/*!*/;
# at 418
#110927 16:53:06 server id 2 end_log_pos 513 Query thread_id=3 exec_time=0 error_code=0
SET TIMESTAMP=1317135186/*!*/;
insert into test3 values (@test)
/*!*/;
# at 513
#110927 16:53:06 server id 2 end_log_pos 540 Xid = 22
COMMIT/*!*/;
# at 540
#110927 16:57:56 server id 2 end_log_pos 599 Query thread_id=3 exec_time=0 error_code=0
SET TIMESTAMP=1317135476/*!*/;
BEGIN
/*!*/;
# at 599
#110927 16:57:56 server id 1 end_log_pos 645 User_var
SET @`test`:=0/*!*/;
# at 645
#110927 16:57:56 server id 2 end_log_pos 740 Query thread_id=3 exec_time=0 error_code=0
SET TIMESTAMP=1317135476/*!*/;
insert into test3 values (@test)
/*!*/;
# at 740
#110927 16:57:56 server id 2 end_log_pos 767 Xid = 30
COMMIT/*!*/;

I have verified this under the following mysql versions:
- mysql-5.1.59
- mysql-5.5.16
- Percona Server 5.1.57-rel12.8
- MariaDB 5.2.7
- MariaDB 5.2.8

I also reported this @ bugs.mysql.com: http://bugs.mysql.com/bug.php?id=62557

Related branches

Changed in percona-server:
status: New → In Progress
assignee: nobody → Alexey Kopytov (akopytov)
milestone: none → 5.1.60-13.1
Changed in percona-server:
status: In Progress → Fix Committed
Revision history for this message
Laurynas Biveinis (laurynas-biveinis) wrote :
tags: added: upstream
Revision history for this message
Shahriyar Rzayev (rzayev-sehriyar) wrote :

Percona now uses JIRA for bug reports so this bug report is migrated to: https://jira.percona.com/browse/PS-2692

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