postgresql

xsrv.postgresql

This role will install PostgreSQL, a relational database management system (RDBMS) emphasizing extensibility and SQL compliance.

It allows running pgmetrics against the PostgreSQL instance.

Requirements/Dependencies/example playbook

See meta/main.yml

# playbook.yml
- hosts: my.CHANGEME.org
  roles:
    - nodiscc.xsrv.common # (required) base server setup, hardening, firewall, bruteforce prevention
    - nodiscc.xsrv.monitoring # (optional) system/server monitoring and health checks
    - nodiscc.xsrv.backup # (optional) automatic backups
    - nodiscc.xsrv.postgresql

# required variables:
# none

See defaults/main.yml for all configuration variables

Usage

Backups

See the included rsnapshot configuration for the backup role.

To backup postgresql data from a remote host with the nodiscc.xsrv.backup role:

# xsrv edit-host default backup.CHANGEME.org
rsnapshot_backup_execs:
  - 'ssh -oStrictHostKeyChecking=no rsnapshot@db.CHANGEME.org /usr/local/bin/postgres-dump-all-databases.sh'
rsnapshot_remote_backups:
  - { user: 'rsnapshot', host: 'db.CHANGEME.org', path: '/var/backups/postgresql' }

# xsrv edit-host default db.CHANGEME.org
  - name: "rsnapshot"
    groups: [ "ssh-access", "sudo", "postgres" ]
    comment: "limited user account for remote backups"
    ssh_authorized_keys: ['data/public_keys/root@backup.CHANGEME.org.pub']
    sudo_nopasswd_commands: ['/usr/bin/rsync', '/usr/bin/psql', '/usr/bin/pg_dump', '/usr/bin/pg_dumpall' ]

Metrics

To install and run pgmetrics against the installed PostgreSQL instance, pass the utils-pgmetrics tag to ansible-playbook:

# using xsrv
TAGS=utils-pgmetrics xsrv deploy
# using ansible-playbook
ansible-playbook playbook.yml --tags=utils-pgmetrics

Upgrading clusters

When upgrading from a Debian release to the next (e.g. Debian 11 to 12), a new version of postgresql server will be installed. However, the previous version will stay installed, and your data will be kept in the cluster managed by the old database engine version. You may want to migrate data from the cluster managed by the "old" version, to a database cluster managed by the new version. You should perform a backup before attempting this operation. In the example below, 13 is the old postgresql version, and 15 is the new postgresql version.

List running clusters:

$ sudo pg_lsclusters
Ver Cluster Port Status Owner    Data directory              Log file
13  main    5432 online postgres /var/lib/postgresql/13/main /var/log/postgresql/postgresql-13-main.log
15  main    5433 online postgres /var/lib/postgresql/15/main /var/log/postgresql/postgresql-15-main.log

Verify that there are no databases in the postgresql 15 cluster:

$ sudo -u postgres psql --cluster 15/main
psql (15.3 (Debian 15.3-0+deb12u1))
Type "help" for help.

postgres=# \l
                                  List of databases
   Name    |  Owner   | Encoding |   Collate   |    Ctype    |   Access privileges
-----------+----------+----------+-------------+-------------+-----------------------
 postgres  | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 |
 template0 | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 | =c/postgres          +
           |          |          |             |             | postgres=CTc/postgres
 template1 | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 | =c/postgres          +
           |          |          |             |             | postgres=CTc/postgres
(3 rows)

postgres=# \q

The postgres, template0 and template1 databases are default databases created on postgresql installation, so in this case, no databases that contain application data are present, and we can go forward with the migration.

Drop the empty postgresql 15 cluster (this will delete all data in the cluster) to make room for the migration:

$ sudo pg_dropcluster --stop 15 main

Then migrate data in the posgtresql 13 cluster to a cluster managed by postgresql 15:

$ sudo -u postgres pg_upgradecluster 13 main
Stopping old cluster...
[...]
Success. Please check that the upgraded cluster works.

Verify that the postgresql 15 cluster has the status online using sudo pg_lsclusters. If not, start it using sudo pg_ctlcluster 15 main start. Verify that your applications work, then drop the postgresql 13 cluster:

$ sudo -u postgres pg_dropcluster 13 main

We can then stop the old postgresql 13 service and remove related packages:

$ sudo systemctl stop postgresql@13-main.service
$ sudo apt purge postgresql*13
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
Note, selecting 'postgresql-13' for glob 'postgresql*13'
Note, selecting 'postgresql-contrib-13' for glob 'postgresql*13'
Note, selecting 'postgresql-client-13' for glob 'postgresql*13'
Note, selecting 'postgresql-doc-13' for glob 'postgresql*13'
Note, selecting 'postgresql-13' instead of 'postgresql-contrib-13'
Package 'postgresql-doc-13' is not installed, so not removed
The following packages will be REMOVED:
  libicu63* libllvm7* postgresql-13* postgresql-client-13*
0 upgraded, 0 newly installed, 4 to remove and 0 not upgraded.
After this operation, 145 MB disk space will be freed.
Do you want to continue? [Y/n] Y

Tags

postgresql - setup postgresql database server
utils-pgmetrics - (manual) get postgresql server metrics

License

GNU GPLv3

References

• https://stdout.root.sx/links/?searchterm=postgres
• https://stdout.root.sx/links/?searchtags=database