How to Migrate an AWS Aurora PostgreSQL Instance from PG13 to PG16

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If you’re planning to upgrade your Aurora PostgreSQL database from version 13 to version 16, the best way to do it with minimal downtime is by using Amazon RDS Blue/Green Deployments. This method creates a nearly seamless switch from your current database to the new version without causing significant interruptions.

Here’s how the process works: first, you set up a synchronized copy of your live database, called the green environment, alongside your current production database, known as the blue environment. You can make updates and test the green environment without affecting your active database. When everything is ready, and the green environment is fully synchronized with the blue, you can quickly switch over to it, minimizing downtime.

If you encounter an error related to the “max_logical_replication_workers” parameter, it usually means there’s a mismatch between your current setup and what’s needed for the upgrade. To fix this, follow these steps:

1. Enable logical replication on your source cluster. Keep in mind, turning on this setting requires a restart of your database instance.

2. Create a new cluster parameter group compatible with PostgreSQL 16. This involves:
– Making a new parameter group for the Aurora PostgreSQL 16 family.
– Activating the “rds.logical_replication” parameter within this group.
– Ensuring the settings are compatible with your existing PostgreSQL 13 configuration.

3. Confirm that your current PostgreSQL 13 version supports Blue/Green deployments. If it doesn’t, you’ll need to perform a small version update first before proceeding.

For more control over the upgrade, you can use logical replication combined with fast cloning. This method involves setting up a publication on your current database, cloning it, upgrading the clone, and then setting up a subscription for replication. While this gives you more manual control, using Blue/Green deployments is usually simpler and managed directly by AWS.

Before starting your upgrade, double-check that your parameter groups are correctly configured and compatible to ensure a smooth transition.

For additional information, you can visit AWS documentation and blogs that detail the steps and best practices for performing these upgrades smoothly.