tutorials

Gene Kranz at his console on May 30, 1965 By NASA; Restored by Adam Cuerden, Public Domain,

The dynamic duo, copyright Federico Campoli

In the previous post we modified the apt role for controlling the setup in a declarative way. Then we added a ssh role for configuring the three devuan servers. The role is used to configure the server’s postgres process owner for ssh passwordless connection.

In this tutorial we’ll complete the setup for the postgres user and then we’ll configure the database clusters with a new role.

In the previous post we configured three devuan servers from scratch using ansible adding the pgdg repository to the apt sources and installing the PostgreSQL binaries.

This tutorial will revisit the apt role’s configuration and will introduce a new role for configuring the postgres operating system’s user for passwordless ssh connections to each other server.

The ansible is a fictional device invented by Ursula K. Le Guin. The ansible allows fast communication between two points across the space, regardless of the distance.

It doesn’t surprise that the Red Hat’s ansible shares the same name as it gives a simple and efficient way to manage servers and automate tasks, yet remaining very lightweight with minimal requirements on the target machines.

Before the release of pg_chameleon 2.0 I had to write an upgrade procedure to allow a smooth migration from the version 1.8.

An interesting challenge I faced was to determine the maximum and minimum position for the MySQL’s binary logs belonging to the same server but stored with different values in multiple sources.

The user defined aggregates, a feature pretty unique to PostgreSQL, allowed me to solve the problem in a robust and simple way.

An ancient italian proverb says Il backup è quella cosa che andava fatta prima. A rough translation could be something like this: the backup is the thing that had to be done before. The concept of backup is quite confusing. Some people wrongly believe that executing a local backup is sufficient to ensure the recover of the data. In the real world a valid backup is present only if three conditions are true.

pgbackrest is an amazing tool that saves entire PostgreSQL clusters with ease. In this post we’ll go trough the configuration of the backup using a remote backup server. For the extensive documentation and detailed instructions please refer to the user guide. operating system configuration For our example we’ll use two virtual machines on virtualbox with devuan 1.0 Jessie installed. Each machine is configured in the same way. 1 cpu 1 GB ram Hard disk of 12 GB with single partition ext4 sshd up and running The machines have one bridged network adapter eth0.

When I started writing pg_chameleon I had in mind a tool making simple to migrate from different dbms engines to PostgreSQL. The name was inspired by the Culture Club’s Karma chameleon song which suggested me the idea of a tool capable to move data between different database technologies. Then tool’s scope changed becoming a replica system rather a migration system but I’ve kept the name as I think the idea is still valid.