Automating checking for new versions of PostgreSQL
Greg Sabino Mullane
July 3, 2013
Hubble image via Flickr user castielstar
It is important to run the latest revision of the major branch of Postgres you are using. While the pgsql-announce mailing list is often touted as a canonical way to become aware of new releases, a better method is to use the check_postgres program, which will let you know if the version you are running needs to be upgraded or not. An example usage:
<span class="gsmp">$</span> check_postgres.pl --action=new_version_pg --dbhost=iroh <span class="gsmo">POSTGRES_NEW_VERSION_PG CRITICAL: Please upgrade to version 9.2.4 of Postgres. You are running 9.2.2</span>
Postgres version numbers come in three sections. The first two indicate the “major version” of Postgres that you are running. The third number indicates the revision. You always want to be using the highest revision available for your version. In the example above, Postgres version 9.2 is being used, and it should be upgraded from revision 2 to revision 4. A change in the revision number is known as a minor release; these are only done for important reasons, such as security or important bug fixes. Read the versioning policy page for more information.
When a new version of PostgreSQL is made, there are two general ways of communicating this fact: the pgsql-announce mailing list, and the versions.rss file on the postgresql.org web site. While the mailing list is low volume, it is not ideal as it contains posts about conferences, and about other Postgres-related software. A better solution is to track the versions.rss file. You could simply subscribe to it, but this will only tell you when the file has been changed. The check_postgres program parses this file and compares the latest revision to the version of Postgres that you are using.
To use it, simply call check_postgres and pass new_version_pg as the action argument, as well as telling check_postgres which PostgreSQL instance you are checking. For example, to check that the Postgres running on your internal host “zuko” is up to date, just run:
check_postgres.pl --action=new_version_pg --dbhost=zuko
Here is what the default output looks like, for both a matching and a non-matching version:
<span class="gsmp">$</span> check_postgres.pl --action=new_version_pg --dbhost=appa <span class="gsmo">POSTGRES_NEW_VERSION_PG CRITICAL: Please upgrade to version 9.2.4 of Postgres. You are running 9.2.2</span> <span class="gsmp">$</span> check_postgres.pl --action=new_version_pg --dbhost=toph <span class="gsmo">POSTGRES_NEW_VERSION_PG OK: Version 9.2.4 is the latest for Postgres</span>
Those examples are very Nagios specific, of course, as evidenced by those uppercase strings at the beginning of the output. If you are using Nagios, it’s a good idea to run this, perhaps once a day or more often. If you are not using Nagios, you can make the output a little cleaner with the --simple argument:
<span class="gsmp">$</span> check_postgres.pl --action=new_version_pg --dbhost=azula <span class="gsmo">Please upgrade to version 9.2.4 of Postgres. You are running 9.2.2</span> <span class="gsmp">$</span> check_postgres.pl --action=new_version_pg --dbhost=sokka <span class="gsmo">Version 9.2.4 is the latest for Postgres</span>
One quick and simple trick is to make this into a cron job and add the --quiet argument, which prevents all output if the check was “OK”. In this way, cron will only send outout (e.g. mail someone) when a new revision has been released. A cron example:
<span class="gsmc">## Twice a day, check that we are running the latest Postgres:</span> 0 7,18 * * * check_postgres.pl --action=new_version_pg --dbhost=cabbage --quiet
Once this alarm goes off, you should strive to update your clusters as soon as possible. If you are using a packaging system, then it may be as simple as relying on it to do the right thing, e.g. “yum update postgresql”. If you are installing from source, you will need the new tarball and can simply “make install” onto the existing Postgres, and then restart it. Always check the release notes for the new revision—once in a blue moon the update requires some other action, such as a reindex of certain types of indexes.