Trusted Postgres Architect v23

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Introduction

TPA is an orchestration tool that uses Ansible to deploy Postgres clusters according to EDB's recommendations.

TPA embodies the best practices followed by EDB, informed by many years of hard-earned experience with deploying and supporting Postgres. These recommendations are as applicable to quick testbed setups as to production environments.

What can TPA do?

TPA is built around a declarative configuration mechanism that you can use to describe a Postgres cluster, from its topology right down to the smallest details of its configuration.

Start by running tpaexec configure to generate an initial cluster configuration based on a few high-level choices (e.g., which version of Postgres to install). The default configuration is ready to use as-is, but you can edit it to suit your needs (the generated configuration is just a text file, config.yml).

Using this configuration, TPA can:

1. Provision servers (e.g., AWS EC2 instances or Docker containers) and any other resources needed to host the cluster (or you can deploy to existing servers or VMs just by specifying connection details).

2. Configure the operating system (tweak kernel settings, create users and SSH keys, install packages, define systemd services, set up log rotation, and so on).

3. Install and configure Postgres and associated components (e.g., PGD, Barman, pgbouncer, repmgr, and various Postgres extensions).

4. Run automated tests on the cluster after deployment.

5. Deploy future changes to your configuration (e.g., changing Postgres settings, installing and upgrading packages, adding new servers, and so on).

How do I use it?

To use TPA, you need to install it and run the tpaexec setup command. Follow the installation instructions for your platform.

TPA operates in four distinct stages to bring up a Postgres cluster:

• Generate a cluster configuration
• Provision servers (VMs, containers) to host the cluster
• Deploy software to the provisioned instances
• Test the deployed cluster

# 1. Configuration: decide what kind of cluster you want
[tpa]$ tpaexec configure clustername --architecture M1 --platform aws \
        --postgresql 14 \
        --failover-manager repmgr

# 2. Provisioning: create the servers needed to host the cluster
[tpa]$ tpaexec provision clustername

# 3. Deployment: install and configure the necessary software
[tpa]$ tpaexec deploy clustername

# 4. Testing: make sure everything is working as expected
[tpa]$ tpaexec test clustername

You can run TPA from your laptop, an EC2 instance, or any machine that can reach the cluster's servers over the network.

Here's a list of capabilities and supported software.

Configuration

The tpaexec configure command generates a simple YAML configuration file to describe a cluster, based on the options you select. The configuration is ready for immediate use, but you can modify it to better suit your needs. Editing the configuration file is the usual way to make any configuration changes to your cluster, both before and after it's created.

At this stage, you must select an architecture and a platform for the cluster. An architecture is a recommended layout of servers and software to set up Postgres for a specific purpose. Examples include "M1" (Postgres with a primary and streaming replicas) and "PGD-Always-ON" (EDB Postgres Distributed 5 in an Always On configuration). A platform is a means to host the servers to deploy any architecture, e.g., AWS, Docker, or bare-metal servers.

Provisioning

The tpaexec provision command creates instances and other resources required by the cluster. The details of the process depend on the architecture (e.g., M1) and platform (e.g., AWS) that you selected while configuring the cluster.

For example, given AWS access with the necessary privileges, TPA will provision EC2 instances, VPCs, subnets, routing tables, internet gateways, security groups, EBS volumes, elastic IPs, etc.

You can also "provision" existing servers by selecting the "bare" platform and providing connection details. Whether these are bare metal servers or those provisioned separately on a cloud platform, they can be used just as if they had been created by TPA.

You are not restricted to a single platform—you can spread your cluster out across some AWS instances (in multiple regions) and some on-premise servers, or servers in other data centres, as needed.

At the end of the provisioning stage, you will have the required number of instances with the basic operating system installed, which TPA can access via SSH (with sudo to root).

Deployment

The tpaexec deploy command installs and configures Postgres and other software on the provisioned servers (which may or may not have been created by TPA; but it doesn't matter who created them so long as SSH and sudo access is available). This includes setting up replication, backups, and so on.

At the end of the deployment stage, Postgres will be up and running.

Testing

The tpaexec test command executes various architecture and platform-specific tests against the deployed cluster to ensure that it is working as expected.

At the end of the testing stage, you will have a fully-functioning cluster.

Incremental changes

TPA is carefully designed so that provisioning, deployment, and testing are idempotent. You can run through them, make a change to config.yml, and run through the process again to deploy the change. If nothing has changed in the configuration or on the instances, then rerunning the entire process will not change anything either.

Cluster management

Once your cluster is up and running, TPA provides convenient cluster management functions, including configuration changes, switchover, and zero-downtime minor-version upgrades. These features make it easier and safer to manage your cluster than making the changes by hand.

Extensible through Ansible

TPA supports a variety of configuration options, so you can do a lot just by editing config.yml and re-running provision/deploy/test. If you do need to go beyond what TPA already supports, you can write

• Custom commands, which make it simple to write playbooks to run on the cluster. Just create commands/xyz.yml in your cluster directory, and invoke it using tpaexec xyz /path/to/cluster. Ideal for any management tasks or processes that you need to automate.

• Custom tests, which augment the builtin tests with in-depth verifications specific to your environment and application. Using tpaexec test to run all tests in a uniform, repeatable way ensures that you will not miss out on anything important, either when dealing with a crisis, or just during routine cluster management.

• Hook scripts, which are invoked during various stages of the deployment. For example, tasks in hooks/pre-deploy.yml will be run before the main deployment; there are many other hooks, including post-deploy. This places the full range of Ansible functionality at your disposal.

It's just Postgres

TPA can create complex clusters with many features configured, but the result is just Postgres. The installation follows some conventions designed to make life simpler, but there is no hidden magic or anything standing in the way between you and the database. You can do everything on a TPA cluster that you could do on any other Postgres installation.

Versioning in TPA

TPA previously used a date-based versioning scheme whereby the major version was derived from the year. From version 23, TPA transitioned to semantic versioning, initially using a two-part major-minor pattern, then adopting full three-part semantic versioning in version 23.34.1. Under this scheme, the major version is only incremented where required to comply with the backward compatibility principle below.

Backwards compatibility

A key development principle of TPA is to maintain backwards compatibility so there is no reason for users to need anything other than the latest version of TPA. We define backwards compatibility as follows:

• A config.yml created with TPA X.a will be valid with TPA X.b where b>=a

• The cluster created from that config.yml will be maintainable and re-deployable with TPA X.b

  Therefore, a new major version implies a break in backward compatibility. As such, we aim to avoid releasing major versions and will only do so in exceptional circumstances.

  Getting started

Follow the TPA installation instructions for your system, then configure your first cluster.