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Commitb4f584f9d2(affecting v15~, later backpatched down to 13 as of3635a0a35a) introduced an unconditional WAL receiver shutdown when switching from streaming to archive WAL sources. This causes problems during a timeline switch, when a WAL receiver enters WALRCV_WAITING state but remains alive, waiting for instructions. The unconditional shutdown can break some monitoring scenarios as the WAL receiver gets repeatedly terminated and re-spawned, causing pg_stat_wal_receiver.status to show a "streaming" instead of "waiting" status, masking the fact that the WAL receiver is waiting for a new TLI and a new LSN to be able to continue streaming. This commit changes the WAL receiver behavior so as the shutdown becomes conditional, with InstallXLogFileSegmentActive being always reset to prevent the regression fixed byb4f584f9d2: only terminate the WAL receiver when it is actively streaming (WALRCV_STREAMING, WALRCV_STARTING, or WALRCV_RESTARTING). When in WALRCV_WAITING state, just reset InstallXLogFileSegmentActive flag to allow archive restoration without killing the process. WALRCV_STOPPED and WALRCV_STOPPING are not reachable states in this code path. For the latter, the startup process is the one in charge of setting WALRCV_STOPPING via ShutdownWalRcv(), waiting for the WAL receiver to reach a WALRCV_STOPPED state after switching walRcvState, so WaitForWALToBecomeAvailable() cannot be reached while a WAL receiver is in a WALRCV_STOPPING state. A regression test is added to check that a WAL receiver is not stopped on timeline jump, that fails when the fix of this commit is reverted. Reported-by: Ryan Bird <ryanzxg@gmail.com> Author: Xuneng Zhou <xunengzhou@gmail.com> Reviewed-by: Noah Misch <noah@leadboat.com> Reviewed-by: Michael Paquier <michael@paquier.xyz> Discussion: https://postgr.es/m/19093-c4fff49a608f82a0@postgresql.org 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. PostgreSQL has many language interfaces, many of which are listed here: https://www.postgresql.org/download/ See the file INSTALL for instructions on how to build and install PostgreSQL. That file also lists supported operating systems and hardware platforms and contains information regarding any other software packages that are required to build or run the PostgreSQL system. Copyright and license information can be found in the file COPYRIGHT. A comprehensive documentation set is included in this distribution; it can be read as described in the installation instructions. The latest version of this software may be obtained at https://www.postgresql.org/download/. For more information look at our web site located at https://www.postgresql.org/.