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PostgreSQL 17-18 major upgrade – blue-green migration with minimal downtime
- PostgreSQL 18 Beta 1 introduces new features like improved IO on reads, pg_createsubscriber, and pg_upgrade options to facilitate smoother major upgrades through blue-green migration using logical replication technology.
- pg_createsubscriber automates setting up logical replication by converting a physical standby server into a logical replica without copying initial table data, simplifying the process, especially for large databases.
- PostgreSQL 18 Beta 1 adds the --all flag to pg_createsubscriber for creating logical replicas for all databases in an instance with a single command, streamlining replication setup in multi-database environments.
- PostgreSQL 18 brings new capabilities to pg_upgrade, such as the --swap option for faster upgrades, along with improvements like pg_stat_subscription_stats, enhancing monitoring of logical replication write conflicts.
- The article outlines a step-by-step blue-green migration process starting with setting up the blue (primary) environment with PostgreSQL 17, configuring replication settings, creating a physical replica (green environment), and transitioning to logical replication.
- The guide covers creating a publication for all tables, using pg_createsubscriber for logical replication setup, upgrading the green environment to PostgreSQL 18 using pg_upgrade with the --swap method, and ensuring successful logical replication post-upgrade.
- The process involves performing failover and cutover to the upgraded green environment after stopping new writes on the primary, syncing latest LSN, dropping subscription, and executing failover commands to switch application traffic to the upgraded instance.
- The article concludes with insights on leveraging blue-green migrations for major version jumps, automation using tools like Ansible playbooks, involving DEV teams for testing post-upgrade, and addressing logical replication limitations.
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