Bill Moran Network Engineer 5849 Forbes Avenue Pittsburgh, PA 15217

slony_switchover.sh

In an effort to make slony disasters easier to manage, I wrote a script called slony_switchover.sh

The problems I was trying to solve:

• I needed something to ensure others could do origin migrations in an emergency in the event that I was on vacation or otherwise unavailable
• Our network topology causes connection paths to vary depending on where you're running the slonik script from, thus each node would need its own slonik script that was different than other nodes
• We replicate many different databases. Combined with the previous issue, this would result in a very large number of scripts or configs to maintain

The script doesn't do anything particularly magical, but I feel that it improves things in the following ways:

• Extremely simply syntax
• Derives most of the required information from the database itself, thus it does not require config files and the small amount of information required to get it started can be specified on the command line or in a .pgpass file
• Intelligent enough to derive the correct connection paths based on the where it's being run from

The script makes several assumptions that I feel are logical. For example, if you want to migrate a database to the server you're working from, and the cluster name is the same as the database name and the user to connect as is "slony", then the following command would do the trick:
slony_switchover.sh -d database_name

Of course, these assumptions don't always hold true, so I designed the script to still be usable. If your cluster is named differnently than the database, the user is "postgres" and you want to move set 4 to node 8, the command line is still pretty simple:
slony_switchover.sh -d database_name -c cluster_name -U postgres -s4 -t8

The script can be downloaded here.

Revision History

• 2008-05-12: Updates from feedback:
  • Bail if any conninfo is missing
  • Use which to find psql instead of assuming the path
  • Extract the list of node IDs from the DB config
• 2008-04-12: Initial Relase

All content copyright Collaborative Fusion, Inc. and Bill Moran. All rights reserved.