Proxy configurator for Patroni managed PostgreSQL clusters.

Pc4Patroni is a simple python script that continuously monitors the configuration of a Patroni managed PostgreSQL cluster and when the master or slaves change it updates the configuration files of your database proxy. Currently it only supports clusters that store their information in Etcd.

The proxy comes with a sample configuration file for PgBouncer. Writing a configuration file for other proxies like HAProxy should be straightforward for someone familiar with the chosen solution. It is designed with the intent to be generic enough to support any proxy without coding changes.

• The following python modules, that can be installed with pip: patroni, jinja2, pyaml
• It is only tested with python 2.7

Installation is currently manual. I copy everything to /opt, copy the config file from extras/settings.yml to /etc/pc4patroni/settings.yml, the configuration template extras/pgbouncer.j2 to /etc/pgbouncer/pcbouncer.j2 .

If your systems uses systemd, you could copy extras/pc4patroni.service to /etc/systemd/system/pc4patroni.service . Next use sudo systemctl daemon-reload to load this config and sudo systemctl start pc4patroni to start it. Otherwise, the way to start it is something like /usr/bin/python /opt/pc4patroni/pc4patrony.py /etc/pc4patroni/settings.yml .

You will probably need to change the sample configurations (the files in the extras folder) to meet your needs.

Please look at the sample configuration file in extras/settings.yml, it contains comments that explain all options.

• pc4patroni does not start the pgbouncer with the included configuration and does not include anything to check if your proxy is running, it only updates the configuration and upon a configuration change it triggers a command of your choice (typically the proxy's reload config command.)
• No attempt is made to parse existing proxy configuration, if the configuration is changed externally pc4patroni will not notice.
• The configurations are always written out and a configuration reload is triggered immediately after restart, even if the proxies configuration was already correct.
• The script is designed to run under the same user as the proxy.
• The scripts polls the configuration (currently form Etcd), so there may be a slight delay (a few seconds) between a failover and a configuration reload.

We have chosen to stick with the license Patroni uses for simplicity: the MIT License.