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A race condition could cause a newly synced replication slot to become invalidated between its initial sync and the checkpoint. When syncing a replication slot to a standby, the slot's initial restart_lsn is taken from the publisher's remote_restart_lsn. Because slot sync happens asynchronously, this value can lag behind the standby's current redo pointer. Without any interlocking between WAL reservation and checkpoints, a checkpoint may remove WAL required by the newly synced slot, causing the slot to be invalidated. To fix this, we acquire ReplicationSlotAllocationLock before reserving WAL for a newly synced slot, similar to commit 006dd4b2e5. This ensures that if WAL reservation happens first, the checkpoint process must wait for slotsync to update the slot's restart_lsn before it computes the minimum required LSN. However, unlike in ReplicationSlotReserveWal(), this lock alone cannot protect a newly synced slot if a checkpoint has already run CheckPointReplicationSlots() before slotsync updates the slot. In such cases, the remote restart_lsn may be stale and earlier than the current redo pointer. To prevent relying on an outdated LSN, we use the oldest WAL location available if it is greater than the remote restart_lsn. This ensures that newly synced slots always start with a safe, non-stale restart_lsn and are not invalidated by concurrent checkpoints. Author: Zhijie Hou <houzj.fnst@fujitsu.com> Reviewed-by: Hayato Kuroda <kuroda.hayato@fujitsu.com> Reviewed-by: Amit Kapila <amit.kapila16@gmail.com> Reviewed-by: Vitaly Davydov <v.davydov@postgrespro.ru> Reviewed-by: Chao Li <li.evan.chao@gmail.com> Backpatch-through: 17 Discussion: https://postgr.es/m/TY4PR01MB16907E744589B1AB2EE89A31F94D7A%40TY4PR01MB16907.jpnprd01.prod.outlook.com
PostgreSQL Database Management System
This directory contains the source code distribution of the PostgreSQL database management system.
PostgreSQL is an advanced object-relational database management system that supports an extended subset of the SQL standard, including transactions, foreign keys, subqueries, triggers, user-defined types and functions. This distribution also contains C language bindings.
Copyright and license information can be found in the file COPYRIGHT.
General documentation about this version of PostgreSQL can be found at https://www.postgresql.org/docs/devel/. In particular, information about building PostgreSQL from the source code can be found at https://www.postgresql.org/docs/devel/installation.html.
The latest version of this software, and related software, may be obtained at https://www.postgresql.org/download/. For more information look at our web site located at https://www.postgresql.org/.