Instance configuration v23

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This page presents an overview of the various controls that TPA offers to customise the deployment process on cluster instances, with links to more detailed documentation.

Before you dive into the details of deployment, it may be helpful to read an overview of configuring a cluster to understand how cluster and instance variables and the other mechanisms in config.yml work together to allow you to write a concise, easy-to-review configuration.

System-level configuration

The first thing TPA does is to ensure that Python is bootstrapped and ready to execute Ansible modules (a distribution-specific process). Then it completes various system-level configuration tasks before moving on to Postgres configuration below.

Package repositories

You can use the pre-deploy hook to execute tasks before any package repositories are configured.

You can use the post-repo hook to execute tasks after package repositories have been configured (e.g., to correct a problem with the repository configuration before installing any packages).

Package installation

Once the repositories are configured, packages are installed at various stages throughout the deployment, beginning with a batch of system packages:

Postgres and other components (e.g., Barman, repmgr, pgbouncer) will be installed separately according to the cluster configuration; these are documented in their own sections below.

Other system-level tasks

Skipping deployment completely

To prevent TPA from doing any part of the deployment process on an instance - in other words, if you want TPA to provision the instance and then leave it alone - set the provision_only setting for the instance to true in config.yml. This setting will make TPA omit the instance entirely from the inventory which tpaexec deploy sees.

Postgres

Postgres configuration is an extended process that goes hand-in-hand with setting up other components like repmgr and pgbouncer. It begins with installing Postgres itself.

Version selection

Use the configure options to select a Postgres flavour and version, or set postgres_version in config.yml to specify which Postgres major version you want to install.

That's all you really need to do to set up a working cluster. Everything else on this page is optional. You can control every aspect of the deployment if you want to, but the defaults are carefully tuned to give you a sensible cluster as a starting point.

Installation

The default postgres_installation_method is to install packages for the version of Postgres you selected, along with various extensions, according to the architecture's needs:

Whichever installation method you choose, TPA can give you the same cluster configuration with a minimum of effort.

Configuration

You can use the postgres-config hook to execute tasks after the Postgres configuration files have been installed (e.g., to install additional configuration files).

Once the Postgres configuration is in place, TPA will go on to install and configure other components such as Barman, repmgr, pgbouncer, and haproxy, according to the details of the architecture.

Other components

Configuring and starting services

TPA will now install systemd service unit files for each service. The service for Postgres is named postgres.service, and can be started or stopped with systemctl start postgres.

In the first deployment, the Postgres service will now be started. If you are running tpaexec deploy again, the service may be reloaded or restarted depending on what configuration changes you may have made. Of course, if the service is already running and there are no changes, then it's left alone.

In any case, Postgres will be running at the end of this step.

After starting Postgres

You can use the postgres-config-final hook to execute tasks after the post-startup Postgres configuration has been completed (e.g., to perform SQL queries to create objects or load data).

You can use the post-deploy hook to execute tasks after the deployment process has completed.