RE: MySQL Failover / Failback

"Jeff Stoner" <jstoner@xxxxxxxxxxxx> · Fri, 1 Jun 2007 18:21:20 +0100

Sounds like you've got several things happening all at 
once. If you are not using MySQL Cluster, then you will probably 
have an active/passive setup, in which MySQL will be running on only one 
node. If you are using MySQL Cluster, why are you using Redhat 
Cluster?

Replication? Are you referring to MySQL Replication? 
What is replicating where? Are the slaves a part of the Redhat Cluster? If you 
simply mean will replication "break" if MySQL fails over then no. Replication on 
the slave will retry connecting to the master (according to the connection retry 
settings in MySQL.) Also, you must use the Redhat Cluster-controlled IP when 
establishing replication and not the IP of any particular node (for obvious 
reasons.)

For my MySQL databases built on Redhat Cluster, I 
specify my service as follows:

<service autostart="1" domain="mysql-fail-domain" 
name="mysql5-service">
   <ip 
ref="10.2.2.2"/>
   <fs ref="mysqlfs"/>

<script ref="mysqld"/>
</service>

The filesystem resource is a slice of SAN accessible by 
all nodes in the cluster. The script is a (modified) /etc/init.d/mysqld 
script.

--Jeff

Service Engineer
OpSource Inc.

"The 
Message of the Day is /etc/motd"

  I am curious if 
  anyone knows the best practices for this? Several use cases 
  include

  Note: We are 
  choosing to use a vip for the two nodes to make the failover change 
  transparent to the application side.

  1) Node 1 (master) 
  dies
          -How do we enable "sticky" 
  failover so that it does not then fail back to Node 1
          -Is Node 2 active all the 
  time or is the service completely shut off? And if its off, how would 
  replication happen?

  -How do failover domains work in this 
  case?
  2) Node 2 (Master) 
  Node 1 recovered

  -How does replication continue 
  again?

  -How does the master slave relationship change? Is 
  this automated, or does it require manual intervention? Should we be using 
  DRDB?
  3) Node 1 (master) 
  Node 2 (slave) - network connectivity dies on node 1

  -There is an IP resource available, but how does this 
  monitor and handle failover?

  -How can I move the vip in the event of a failure? Do 
  I need to manually script this?

  With the vip 
  failover, do I attach the vip resource to the mysql resource in the failover 
  domain for those two nodes? What happens if I do this?

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