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WaitLSNWakeup() removes a waiter from the heap before setting its latch. If the position that caused the wakeup moves backwards before the waiter rechecks it, as can happen when WAL streaming restarts, the waiter may sleep again while no longer registered. Subsequent WAL progress then cannot wake it. When an unmet waiter finds that it is no longer in the heap, add it back and restart the loop. Rereading the position after registration also prevents missing an advance between the previous read and the re-add. Process interrupts before re-registering rather than after, so that a wakeup which goes stale again cannot postpone cancellation, however often it repeats. As a side effect, a pending cancel now wins over an expired timeout, which previously reported a timeout instead. Add deterministic TAP coverage that simulates a stale standby_write wakeup without advancing the actual write or replay positions. Author: Xuneng Zhou <xunengzhou@gmail.com> Reviewed-by: Alexander Korotkov <aekorotkov@gmail.com> Discussion: https://postgr.es/m/CABPTF7UtW_cAa%3DQh4RDfKiUqu3pJJE22ai9tbWJVERbeRyssLw%40mail.gmail.com Backpatch-through: 19
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/.