883a95646a
Previously, when the replay LSN reported in feedback messages from a standby stopped advancing, for example, due to a recovery conflict, the write_lag and flush_lag columns in pg_stat_replication would initially update but then stop progressing. This prevented users from correctly monitoring replication lag. The problem occurred because when any LSN stopped updating, the lag tracker's cyclic buffer became full (the write head reached the slowest read head). In that state, the lag tracker could no longer compute round-trip lag values correctly. This commit fixes the issue by handling the slowest read entry (the one causing the buffer to fill) as a separate overflow entry and freeing space so the write and other read heads can continue advancing in the buffer. As a result, write_lag and flush_lag now continue updating even if the reported replay LSN remains stalled. Backpatch to all supported versions. Author: Fujii Masao <masao.fujii@gmail.com> Reviewed-by: Chao Li <lic@highgo.com> Reviewed-by: Shinya Kato <shinya11.kato@gmail.com> Reviewed-by: Xuneng Zhou <xunengzhou@gmail.com> Discussion: https://postgr.es/m/CAHGQGwGdGQ=1-X-71Caee-LREBUXSzyohkoQJd4yZZCMt24C0g@mail.gmail.com Backpatch-through: 13
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.
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