Future PostgreSQL: Improvement to the Replication Protocol
Check out the latest improvement to PostgreSQL replication to which our OSPO team contributed to help solve reliability problems.
Today's post is about a new PostgreSQL feature (coming in PostgreSQL 15) developed by Aiven to solve a reliability problem we sometimes run into with replication. The READ_REPLICATION_SLOT command makes a physical replication client, particularly pg_receivewal, more reliable.
At Aiven's OSPO office, we dedicate our time to the open source products Aiven offers or develops, and we were very happy to collaborate on this feature.
This story starts with our own PgHoard, a PITR backup tool for PostgreSQL. PgHoard offers several methods to archive the WAL (Write Ahead Log), including pg_receivewal, a small application shipping with PostgreSQL which connects to a PostgreSQL cluster using the physical replication protocol to stream WAL as they are produced, optionally keeping track of the position on the server using a replication slot.
We noticed that we could occasionally lose some WAL when PgHoard is restarted on another machine. This happens because pg_receivewal determines its start position like this:
