Upgrading your cluster v23.40.0

The tpaexec upgrade command is used to upgrade the software running on your TPA cluster (tpaexec deploy will not perform upgrades).

(This command replaces the earlier tpaexec update-postgres command.)

Introduction

If you make any changes to config.yml, the way to apply those changes is to run tpaexec provision followed by tpaexec deploy.

The exception to this rule is that tpaexec deploy will refuse to install a different version of a package that is already installed. Instead, you must use tpaexec upgrade to perform software upgrades.

This command will try to perform the upgrade with minimal disruption to cluster operations. The exact details of the specialised upgrade process depend on the architecture of the cluster, as documented below.

When upgrading, you should always use barman to take a backup before beginning the upgrade and disable any scheduled backups which would take place during the time set aside for the upgrade.

In general, TPA will proceed instance-by-instance, stopping any affected services, installing new packages, updating the configuration if needed, restarting services, and performing any runtime configuration changes, before moving on to do the same thing on the next instance. At any time during the process, only one of the cluster's nodes will be unavailable.

When upgrading a cluster to PGD-Always-ON or upgrading an existing PGD-Always-ON cluster, you can enable monitoring of the status of your proxy nodes during the upgrade by adding the option -e enable_proxy_monitoring=true to your tpaexec upgrade command line. If enabled, this will create an extra table in the bdr database and write monitoring data to it while the upgrade takes place. The performance impact of enabling monitoring is very small and it is recommended that it is enabled.

Configuration

In many cases, minor-version upgrades do not need changes to config.yml. Just run tpaexec upgrade, and it will upgrade to the latest available versions of the installed packages in a graceful way (what exactly that means depends on the details of the cluster).

Sometimes an upgrade involves additional steps beyond installing new packages and restarting services. For example, in order to upgrade from BDR4 to PGD5, one must set up new package repositories and make certain changes to the BDR node and group configuration during the process.

In such cases, where there are complex steps required as part of the process of effecting a software upgrade, tpaexec upgrade will perform those steps. For example, in the above scenario, it will configure the new PGD5 package repositories (which deploy would also normally do).

However, it will make only those changes that are directly required by the upgrade process itself. For example, if you edit config.yml to add a new Postgres user or database, those changes will not be done during the upgrade. To avoid confusion, we recommend that you tpaexec deploy any unrelated pending changes before you begin the software upgrade process.

Upgrading from BDR-Always-ON to PGD-Always-ON

To upgrade from BDR-Always-ON to PGD-Always-ON (that is, from BDR3/4 to PGD5), first run tpaexec reconfigure:

$ tpaexec reconfigure ~/clusters/speedy\
  --architecture PGD-Always-ON\
  --pgd-proxy-routing local

This command will read config.yml, work out the changes necessary to upgrade the cluster, and write a new config.yml. For details of its invocation, see the command's own documentation. After reviewing the changes, run tpaexec upgrade to perform the upgrade:

$ tpaexec upgrade ~/clusters/speedy\

Or to run the upgrade with proxy monitoring enabled,

$ tpaexec upgrade ~/clusters/speedy\
  -e enable_proxy_monitoring=true

tpaexec upgrade will automatically run tpaexec provision, to update the ansible inventory. The upgrade process does the following:

1. Checks that all preconditions for upgrading the cluster are met.
2. For each instance in the cluster, checks that it has the correct repositories configured and that the required postgres packages are available in them.
3. For each BDR node in the cluster, one at a time:
   • Fences the node off to ensure that harp-proxy doesn't send any connections to it.
   • Stops, updates, and restarts postgres, including replacing BDR4 with PGD5.
   • Unfences the node so it can receive connections again.
   • Updates pgbouncer and pgd-cli, as applicable for this node.
4. For each instance in the cluster, updates its BDR configuration specifically for BDR v5
5. For each proxy node in the cluster, one at a time:
   • Sets up pgd-proxy.
   • Stops harp-proxy.
   • Starts pgd-proxy.
6. Removes harp-proxy and its support files.

Upgrading from PGD-Always-ON to PGD-X

Upgrading a PGD-Always-ON cluster to PGD-X is a significant architectural evolution, involving changes beyond a simple software update. It is a carefully orchestrated, multi-stage process that requires reconfiguring your cluster in distinct phases before the final software upgrade can take place. The procedure first modernizes your PGD 5 cluster's connection handling by replacing pgd-proxy with the built-in Connection Manager–a step that currently requires manual operations on the live cluster but is planned for automation in a future TPA release–and then transitions the cluster to the new PGD-X architecture.

The upgrade process transitions the cluster through three distinct states:

1. Start: PGD 5.9+ (PGD-Always-ON) using PGD-Proxy
2. Intermediate: PGD 5.9+ (PGD-Always-ON) now using the built-in Connection Manager
3. Final: PGD 6 (PGD-X Architecture)

Prerequisites

Before you begin, ensure you have met the following requirements:

• Cluster Version: Your cluster must be running PGD version 5.9 or later. If you are on an earlier 5.x version, use tpaexec upgrade to upgrade to the latest minor version first. See the section (#pgd-always-on) for details on minor version upgrade of a PGD-Always-ON cluster.

• Backup: You have a current, tested backup of your cluster.

• Review Overrides: You have reviewed your config.yml for any instance-level proxy overrides (e.g., pgd_proxy_options). These cannot be migrated automatically and will require manual intervention.

• Co-hosted Proxies: Your PGD 5 cluster must be configured with co-hosted proxies (where the pgd-proxy role is on the same instance as the bdr role). Standalone proxy instances are not supported by this upgrade path.

Stage 1: Migrating to the Built-in Connection Manager

The first stage is to reconfigure your PGD 5.9+ cluster to switch from using the external pgd-proxy to the modern, built-in Connection Manager.

Step 1.1: Reconfigure for Connection Manager

Run the following command to update your config.yml file. This adds the settings required to enable the built-in Connection Manager.

This action only modifies the configuration file; it does not change the running state of your database cluster yet.

Before writing the new version, reconfigure automatically saves a backup of the current file (e.g., config.yml.~1~), providing a safe restore point.

For details of its invocation, see the command's own documentation.

$ tpaexec reconfigure ~/clusters/speedy --enable-connection-manager

Step 1.2: Apply the Configuration and Activate Connection Manager

Apply the configuration changes to your live cluster. This is a manual operational task that involves, adding Postgres configuration parameter, stopping the pgd-proxy service and restarting PostgreSQL nodes in a rolling fashion to activate the Connection Manager.

For the detailed, step-by-step instructions for this process, please follow the official Connection Manager Migration Guide.

Stage 1 Complete

At the end of this stage, you will have a PGD cluster running with the built-in Connection Manager. This is an intermediate state, and you should proceed directly to Stage 2. While tpaexec upgrade for minor version upgrades is not supported in this intermediate state, we also advise agaist running tpaexec deploy until the upgrade to PGD 6 is complete.

Stage 2: Upgrading the Architecture to PGD-X

Once your cluster is running with the Connection Manager, you can proceed with the final configuration step to prepare for the PGD 6 upgrade.

Step 2.1: Reconfigure for the PGD-X Architecture

Run the following command to update your config.yml for the new architecture. This changes the cluster architecture type, sets the BDR version to 6, and removes any obsolete legacy settings.

This action only modifies the configuration file; it does not change the running state of your database cluster yet.

$ tpaexec reconfigure ~/clusters/speedy --architecture PGD-X

Step 2.2: Perform the Software Upgrade

After reviewing the final changes in config.yml, you can now run the standard tpaexec upgrade command. This will perform the software upgrade on all nodes, bringing your cluster to PGD 6.

$ tpaexec upgrade ~/clusters/speedy

Or to run the upgrade with proxy monitoring enabled,

$ tpaexec upgrade ~/clusters/speedy\
  -e enable_proxy_monitoring=true

tpaexec upgrade will automatically run tpaexec provision, to update the ansible inventory. The upgrade process does the following:

1. Checks that all preconditions for upgrading the cluster are met.
2. For each instance in the cluster, checks that it has the correct repositories configured and that the required postgres packages are available in them.
3. For each BDR node in the cluster, one at a time:
   • Fences the node off so there are no connections to it.
   • Stops, updates, and restarts postgres, including replacing PGD5 with PGD6.
   • Unfences the node so it can receive connections again.
   • Updates pgbouncer and pgd-cli, as applicable for this node.
4. Applies BDR configuration specifically for BDR v6

Upgrade Complete

Your cluster is now running PGD 6 with the PGD-X architecture and is fully manageable with both tpaexec deploy and tpaexec upgrade as usual.

PGD-Always-ON

When upgrading an existing PGD-Always-ON (PGD5) cluster to the latest available software versions, the upgrade process does the following:

1. Checks that all preconditions for upgrading the cluster are met.
2. For each instance in the cluster, checks that it has the correct repositories configured and that the required postgres packages are available in them.
3. For each BDR node in the cluster, one at a time:
   • Fences the node off to ensure that pgd-proxy doesn't send any connections to it.
   • Stops, updates, and restarts postgres.
   • Unfences the node so it can receive connections again.
   • Updates pgbouncer, pgd-proxy, and pgd-cli, as applicable for this node.

BDR-Always-ON

For BDR-Always-ON clusters, the upgrade process goes through the cluster instances one by one and does the following:

1. Tell haproxy the server is under maintenance.
2. If the instance was the active server, request pgbouncer to reconnect and wait for active sessions to be closed.
3. Stop Postgres, update packages, and restart Postgres.
4. Finally, mark the server as "ready" again to receive requests through haproxy.

PGD logical standby or physical replica instances are updated without any haproxy or pgbouncer interaction. Non-Postgres instances in the cluster are left alone.

M1

For M1 clusters, upgrade will first update the streaming replicas and witness nodes when applicable, then perform a switchover from the primary to one of the upgraded replicas, update the primary, and switchover back to the initial primary node.

Controlling the upgrade process

You can control the order in which the cluster's instances are upgraded by defining the update_hosts variable:

$ tpaexec upgrade ~/clusters/speedy \
  -e update_hosts=quirk,keeper,quaver

This may be useful to minimise lead/shadow switchovers during the upgrade by listing the active PGD primary instances last, so that the shadow servers are upgraded first.

If your environment requires additional actions, the postgres-pre-update and postgres-post-update hooks allow you to execute custom Ansible tasks before and after the package installation step.

Upgrading a Subset of Nodes

You can perform a rolling upgrade on a subset of instances by setting the update_hosts variable. However, support for this feature varies by architecture.

• For the M1 architecture, this feature is supported in all its upgrade scenarios.

• For PGD-Always-ON/BDR-Always-ON, this is supported only during minor version upgrades.

Best Practice for PGD-Always-ON/BDR-Always-ON

When performing a minor upgrade on a subset of PGD nodes, it is highly recommended to update the RAFT leader nodes last. This strategy avoids potential issues with post-upgrade checks while the cluster is running mixed versions of BDR.

Package version selection

By default, tpaexec upgrade will update to the latest available versions of the installed packages if you did not explicitly specify any package versions (e.g., Postgres, PGD, or pglogical) when you created the cluster.

If you did select specific versions, for example by using any of the --xxx-package-version options (e.g., postgres, bdr, pglogical) to tpaexec configure, or by defining xxx_package_version variables in config.yml, the upgrade will do nothing because the installed packages already satisfy the requested versions.

In this case, you must edit config.yml, remove the version settings, and re-run tpaexec provision. The update will then install the latest available packages. You can still update to a specific version by specifying versions on the command line as shown below:

$ tpaexec upgrade ~/clusters/speedy -vv         \
  -e postgres_package_version="2:11.6r2ndq1.6.13*"      \
  -e pglogical_package_version="2:3.6.11*"              \
  -e bdr_package_version="2:3.6.11*"

Please note that version syntax here depends on your OS distribution and package manager. In particular, yum accepts *xyz* wildcards, while apt only understands xyz* (as in the example above).

Note: see limitations of using wildcards in package_version in tpaexec-configure.

It is your responsibility to ensure that the combination of Postgres, PGD, and pglogical package versions that you request are sensible. That is, they should work together, and there should be an upgrade path from what you have installed to the new versions.

For PGD clusters, it is a good idea to explicitly specify exact versions for all three components (Postgres, PGD, pglogical) rather than rely on the package manager's dependency resolution to select the correct dependencies.

We strongly recommend testing the upgrade in a QA environment before running it in production.