MySQL – Rebuild Slave Adding innodb_file_per_table Without Locking Master

innodbMySQLmysqldumpreplication

I would like to rebuild a mysql slave, adding innodb_file_per_table to the configuration in order to reduce the disk space used (idbdata1 has grown a lot). I want to do it without locking the master's tables and I sketched up a procedure that seems to work, but I would like to know if it is really accurate. I tested this on two vms.

Here are the configurations for the test:

On the master:

server-id               = 10
log_bin                 = /var/log/mysql/mysql-bin.log
expire_logs_days        = 10
max_binlog_size         = 100M
binlog_do_db            = test
#binlog_ignore_db       = include_database_name

On the slave:

server-id               = 20
log_bin                 = /var/log/mysql/mysql-bin.log
relay_log               = /var/log/mysql/mysql-relay-bin.log
expire_logs_days        = 10
max_binlog_size         = 100M
binlog_do_db            = test

Before starting the procedure:

On the slave:

Seconds_Behind_Master: 0

At this point, this is the procedure I tried to rebuild the slave with the new configuration and then let him resume the replication where it stopped

on the slave: stop slave
on the master: insert into t1 values (4,1) # I insert values in tables t1 in database test to validate that the slave is able to recover the replication data that occured during the process
on the slave: mysqldump -u root -p --opt test > test_slave.sql
on the master: insert into t1 values (5,1)
on the slave: drop database test
on the master: insert into t1 values (6,1)
on the slave:

change configuration to set innodb_file_per_table:

innodb_file_per_table
innodb_flush_method=O_DIRECT

on the master: insert into t1 values (7,1)
on the slave:

store bin log replication position from the last stop slave:

mysql -u root -p -e "show slave status \G;" > status

on the slave: service mysql restart
on the slave: stop slave
on the master: insert into t1 values (8,1)
on the slave:

create database && import dump:

mysql -u root -p -e "create database test;"
mysql -u root -p -b test < test_slave.sql

on the master: insert into t1 values (9,1)
on the slave:

reconfigure the replication to start from the last stop slave position (with the master_log_pos and master_log_file stored in the status file):

change master to MASTER_HOST='db01',MASTER_USER='myuser',MASTER_PASSWORD='mypasswd',MASTER_LOG_FILE='mysql-bin.000004',MASTER_LOG_POS=477;

on the slave: start slave

After the 16th step, all inserts made on the master during the process appear in test.t1 on the slave and the replication is working.

               Slave_IO_State: Waiting for master to send event
             Slave_IO_Running: Yes
            Slave_SQL_Running: Yes
        Seconds_Behind_Master: 0
Master_SSL_Verify_Server_Cert: No
             Master_Server_Id: 10

It appears to be successful. However, if someone sees a pitfall in this procedure (that I can't see on this limited lab environment) it would be great to share 🙂

Thank you,

Best Answer

really all could be shorter:

Stop mysql on Slave, change settings, Start MySQL on Slave
Login to MySQL; Stop slave; exit from mysql client
make dump from Master direct from Slave:

mysqldump --host=Master_IP --port=Master_port -u user_with_enought_rights -p --single-transaction --all-databases --master-data=1 > dump.sql

restore dump on Slave

mysql -u root -p < dump.sql

start Slave

It will not lock master (in case of InnoDB tables) and automatically adjust Slave to Master position

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Mysql – Create a thesql slave database from master database

Going by your question, I will like to review what I believe you did thus far:

You stopped mysql on the Master
You copied Master's /var/lib/mysql to the Slave's /var/lib/mysql
I surmise the binlogs on the Master were copied as well

Look at the Slave's last binlog. From the question, it should be

mydbm1-bin.008524
Filesize 1330529

Believe it or not, you have to do a few things:

1) On the Master, create a replication user like this:

GRANT REPLICATION SLAVE,REPLICATION CLIENT
ON *.* TO replicator@'%'
IDENTIFIED BY 'r3plic4t0R';

2) Make /var/lib/mysql on the Slave owned by mysql user

chown -R mysql:mysql /var/lib/mysql

3) Make sure Master's server_id is explicitly set in my.cnf

[mysqld]
server_id = 1

4) Make sure Slave's server_id is explicitly set in my.cnf

[mysqld]
server_id = 2

5) Startup mysql on the Slave

service mysql start

6) Setup replication by running this on the Slave

CHANGE MASTER TO
MASTER_HOST='IPAddressOfMaster',
MASTER_PORT=3306,
MASTER_USER='replicator',
MASTER_PASSWORD='r3plic4t0R',
MASTER_LOG_FILE='mydbm1-bin.008524',
MASTER_LOG_POS=1330529;
START SLAVE;
SELECT SLEEP(5);
SHOW SLAVE STATUS\G

You will see something like this:

mysql> show slave status\G
*************************** 1. row ***************************
             Slave_IO_State: Waiting for master to send event
                Master_Host: 10.48.20.253
                Master_User: replicant
                Master_Port: 3306
              Connect_Retry: 60
            Master_Log_File: mysql-bin.000254
        Read_Master_Log_Pos: 858190247
             Relay_Log_File: relay-bin.066069
              Relay_Log_Pos: 873918
      Relay_Master_Log_File: mysql-bin.000254
           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: 858190247
            Relay_Log_Space: 873772
            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
1 row in set (0.00 sec)

If Slave_IO_Running and Slave_SQL_Running are both Yes, CONGRATULATIONS !!!

I already answered a post back on Feb 06, 2012 ( How to setup replication(Master/slave) in MySQL 5.5.20? ) with essentially the same steps.

I wanted to add additional posts I made for setting up Circular Replication should you decide to setup the two DB servers as Master/Master

Sep 24, 2012 : Setting up MySQL circular replication in existing replication topology?
May 07, 2012 : Setting Circular Replication in mysql

Mysql – Broken thesql replication on slave server (error 1236)

I believe the log file and position need to be specified with the host.

Try:

CHANGE MASTER TO MASTER_HOST='192.168.1.105', MASTER_USER='slaveuser', MASTER_PASSWORD='mypassword', MASTER_LOG_FILE='mysql-bin.000001', MASTER_LOG_POS=107;

Best Answer

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Mysql – Broken thesql replication on slave server (error 1236)

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