PgCommon::get_cluster_socketdir depends on unix_socket_directories setting

[Alex Tomic]

If postgresql.conf does not contain a unix_socket_directories setting, and the /var/run/postgresql directory does not exist, postgresql startup will fail due to underlying postgresql utilties throwing a "Cannot stat /var/run/postgresql" error.

The issue is easy to reproduce:

$ sudo /etc/init.d/postgresql stop
$ sudo rm -rf /var/run/postgresql
$ sudo perl -pi -e 's/unix_socket_directories/#unix_socket_directories/g' /etc/postgresql/9.3/main/postgresql.conf
$ psql --version
Error: Cannot stat /var/run/postgresql
$ pg_lsclusters
Error: Cannot stat /var/run/postgresql

pg_lsclusters is especially important, because it is run inside the postgresql init.d script *before* the /var/run/postgresql directory is recreated.

Adding the unix_socket_directories setting to postgresql.conf is a simple workaround. Filing this bug more for documentation purposes.

[Martin Pitt (pitti)]

To be honest this is mostly a wontfix. Either you do use the postgresql-common integration tools, then we need to assume that the config files from pg_createcluster don't get broken. Or you don't use the postgresql-common tools and do everything by yourself, that's also okay. But mixing the two is just too brittle, as there are so many combinations that it's hard to impossible to test them all.