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• We will rely on Mysql's Connector properties to achieve Master-Master DB HA
  • Look at the following link to know the parameters used to achieve HA using mysql connector
    http://dev.mysql.com/doc/refman/5.0/en/connector-j-reference-configuration-properties.html
• We need to have at least 2 nodes which are connected through 2-way replication and should be consecutive in connector's url
  • look at the following urlss to setup Mysql replication
    http://dev.mysql.com/doc/refman/5.0/en/replication-howto.html
    https://wikis.oracle.com/display/CommSuite/MySQL+High+Availability+and+Replication+Information+For+Calendar+Server
    
• The following configuration need to be done in my.cnf of each mysql server to clean up bin log files automatically.
  

  expire_logs_days=10 (Number of days to keep the bin log files)

  max_binlog_size=100M (The max size of each bin log file)

• To change the bin log files location please use the following property in my.cnf of each mysql server
  log-bin=/var/lib/mysql/binlog/bin-log  (Remember here “bin-log” is the file prefix)

my.cnf Configuration Details (Asynchronous)

The mysql configuration to support DB HA in mysql server is goes into /etc/my.cnf file and varies a little bit between master and slave.

1. Master :
   [mysqld]
   datadir=/var/lib/mysql
   socket=/var/lib/mysql/mysql.sock
   # Disabling symbolic-links is recommended to prevent assorted security risks
   symbolic-links=0
   # Settings user and group are ignored when systemd is used.
   # If you need to run mysqld under a different user or group,
   # customize your systemd unit file for mysqld according to the
   # instructions in http://fedoraproject.org/wiki/Systemd
   server-id=1
   default-storage-engine=InnoDB
   character-set-server=utf8
   transaction-isolation=READ-COMMITTED
   log-bin=mysql-bin
   innodb_flush_log_at_trx_commit=1
   sync_binlog=1
   binlog-format=ROW
   #Bin logs cleanup configuration
   expiry_logs_days=10
   max_binlog_size=100M
   
   [mysqld_safe]
   log-error=/var/log/mysqld.log
   pid-file=/var/run/mysqld/mysqld.pid
   
2. Slave
   [mysqld]
   datadir=/var/lib/mysql
   socket=/var/lib/mysql/mysql.sock
   # Disabling symbolic-links is recommended to prevent assorted security risks
   symbolic-links=0
   # Settings user and group are ignored when systemd is used.
   # If you need to run mysqld under a different user or group,
   # customize your systemd unit file for mysqld according to the
   # instructions in http://fedoraproject.org/wiki/Systemd
   server-id=2
   default-storage-engine = InnoDB
   character-set-server = utf8
   transaction-isolation = READ-COMMITTED
   log-bin=mysql-bin
   innodb_flush_log_at_trx_commit=1
   sync_binlog=1
   binlog-format=ROW
   #Parameters to solve split brain problem
   auto_increment_increment=10
   auto_increment_offset=2
   #Bin logs cleanup configuration
   expiry_logs_days=10
   max_binlog_size=100M
   [mysqld_safe]
   log-error=/var/log/mysqld.log
   pid-file=/var/run/mysqld/mysqld.pid
   

Limitations/Things DBHA is not supported

• Currently Monitoring of Slave by admin is not possible
• Monitoring events are not integrated with MSSplit Brain problem will cause the sync issues

Appendix

• What if I want to do a Manual Switch over from Master-1 to Master-2?
  • Put a 2 way replication as above and do not enable the db ha in db.properties. I.e put the value false against the following property in db.properties
    db.ha.enabled=false

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