If we want to run the application presented in "Writing a Fault-tolerant Database Application using MySQL Fabric" with MySQL Fabric 1.4.2 Release Candidate, some changes to the application are required. In the previous post, we used MySQL Fabric 1.4.0 Alpha and many changes have been made since this version. We can find an updated version of the application here:

• Updated application, ready to use with MySQL Fabric 1.4.2 Release Candidate.

Recall that the application creates a simple database, a high availability group, registers the MySQL Servers into Fabric and runs a thread that mimics a client and another one that periodically executes a switch …

Applications should be written taking into account that errors will eventually happen and, in particular, database application developers usually consider this while writing their applications.

Although the concepts required to write such applications are commonly taught in database courses and to some extent are widely spread, building a reliable and fault-tolerant database application is still not an easy task and hides some pitfalls that we intend to highlight in this post with a set of suggestions or tips.

In what follows, we consider that the execution flow in a database application is characterized by two distinct phases: connection and business logic. In the connection phase, the application connects to a database, sets up the environment and passes the control to the business logic phases. In this phase, it gets inputs from a source, which may be an operator, another application or a component within the same …

In this post, we are going to show how to develop fault-tolerant applications using MySQL Fabric, or simply Fabric, which is an approach to building high availability sharding solutions for MySQL and that has recently become available for download as a labs release (http://labs.mysql.com/). We are going to focus on Fabric's high availability aspects but to find out more on sharding readers may check out the following blog post:

•  http://vnwrites.blogspot.com/2013/09/mysqlfabric-sharding-introduction.html

Servers managed by Fabric are registered in a MySQL Server instance, called backing store, and are …

The occurrence of failures and crashes can compromise the high availability of your database system affecting your revenue and reputation. Therefore, it is fundamental to minimize downtime and have an efficient strategy for crash recovery.

Replication and failover are commonly applied to deal with those situations. However, other types of failures can also affect the recovery process. In fact, the occurrence of unanticipated faults can really be an headache! Thus, it is better to be prepared and implement a good fault-tolerant failover strategy.

Performing failover is not trivial. It requires the execution of several steps in order to ensure data consistency (i.e., no data loss) -- especially if the "best" candidate to become the new master is not the most up-to-date.

Note that, one might desire that the slave with the best hardware should become the new master. In this case, the candidate must be …