====== First Setup preparation ======


On all servers of the (future) cluster issue

  CREATE USER 'replica'@'%' IDENTIFIED BY 'somethinglongandrandom';
  GRANT REPLICATION SLAVE ON *.* TO 'replica'@'80.93.25.175' IDENTIFIED BY 'somethinglongandrandom';

Rapeat latest statement substituting 80.93.25.175 with all of your cluster slave servers

====== Setup/Repair ======

On all servers issue:
  STOP SLAVE;

This is the full step-by-step procedure to resync a master-slave replication from scratch:

At the master:

  RESET MASTER;
  FLUSH TABLES WITH READ LOCK;
  SHOW MASTER STATUS;

And **copy the values of the result of the last command** somewhere.

**Wihtout closing the connection** to the client (because it would release the read lock) issue the command to get a dump of the master:

  mysqldump -uroot -p --skip-add-locks --all-databases > mysqldump.sql


Now you can **release the lock**. To do it perform the following command in the mysql client:

  UNLOCK TABLES;

Now copy the dump file to the slave using scp or your preferred tool.

At the slave:

Lock-out all network connections to ther database to avoid writes before cluster syncronization. You can use //**iptables**// and drop all conections to tcp port 3306 exept from localhost (127.0..0.1).

Open a connection to mysql and type:

  STOP SLAVE;
  RESET SLAVE;

Load master's data dump:

  mysql -uroot -p < mysqldump.sql

If you use Debian, it's likely you have overwritten the local debian sysmaint user password.
Reset it using the one from the /etc/mysql/debian.cnf file.

The first time issue:

  CHANGE MASTER TO
    MASTER_HOST='deimos.units.it',
    MASTER_USER='xxxxxxxxx',
    MASTER_PASSWORD='xxxxxxxxxx',
    MASTER_PORT=3306,
    MASTER_LOG_FILE='mysql-bin.000001',
    MASTER_LOG_POS=106;

subsequent times issue:
  CHANGE MASTER TO MASTER_LOG_FILE='mysql-bin.000001', MASTER_LOG_POS=106;
  


Where the values of the above fields are the ones you copied before.

Finally type

  START SLAVE;

Re enable network connections to other cluster nodes.

And to check that everything is working again, if you type

  SHOW SLAVE STATUS \G;

you should see:

  Slave_IO_Running: Yes
  Slave_SQL_Running: Yes

That's it!

Don't forget to re-enable network connections to clients!


====== What's next ======


For each new server (or on the first server if you need multimaster or circular replication) do the
  STOP SLAVE;

on its source, without closing connection afterward, issue 
  RESET MASTER;
  FLUSH TABLES WITH READ LOCK;
  SHOW MASTER STATUS;
  
on the new server:
  STOP SLAVE;
  RESET SLAVE;
  CHANGE MASTER TO MASTER_LOG_FILE='mysql-bin.000001', MASTER_LOG_POS=106; 
  START SLAVE;

check with
  SHOW SLAVE STATUS \G;

on its source don't forget to issue 
   UNLOCK TABLES;