Fast Read Scaling with repmgr
The features in PostgreSQL 9 allow replication to systems whose only communication with the master are files sent to it, and you can then run queries against that copy. repmgr is free software to make building read scalable clusters of PostgreSQL nodes using this feature simpler to get started with, and then manage in production.
Once you have multiple nodes in a cluster like this, there are several common concerns that everyone encounters. How do you monitor lag between the servers? How do you gracefully switchover to a new master? And when your master fails, how do you promote one of the standby systems to that role, and then get all of the other standby systems to start talking to it?
The repmgr software is a PostgreSQL add-on that lives outside the database to make these chores easier to do. It automatically computes and reports on lag in human-readable units. It includes a monitoring daemon that tracks node state across the whole cluster. Using a simple command line interface, you can execute complicated operations that touch every node in the cluster all from one place. And the V2.0 release adds unique automatic fail-over capabilities.
This talk will introduce how to setup a cluster with repmgr and what sort of tasks you can expect it to help automate. If you're concerned you'll find yourself in a difficult situation where you need to make decisions like "which node has the most recent copy of my data now that the master has failed?" and then shuffle around the configuration of every remaining node, you'll have just the right tool needed for that type of problem. You'll also learn how replication monitoring has changed in PostgreSQL 9.1, and how repmgr fits into the newer toolkit provided by that version.