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The main motivation for this change is to have a process that can serialize stats after all other processes have terminated. Serializing stats already happens in checkpointer, even though walsenders can be active longer. The only reason the current shutdown sequence does not actively cause problems is that walsender currently does not generate any stats. However, there is an upcoming patch changing that. Another need for this change originates in the AIO patchset, where IO workers (which, in some edge cases, can emit stats of their own) need to run while the shutdown checkpoint is being written. This commit changes the shutdown sequence so checkpointer is signalled (via SIGINT) to trigger writing the shutdown checkpoint without also causing checkpointer to exit. Once checkpointer wrote the shutdown checkpoint it notifies postmaster via PMSIGNAL_XLOG_IS_SHUTDOWN and waits for the termination signal (SIGUSR2, as before). Checkpointer now is terminated after all children, other than dead-end children and logger, have been terminated, tracked using the new PM_WAIT_CHECKPOINTER PMState. Reviewed-by: Heikki Linnakangas <hlinnaka@iki.fi> Reviewed-by: Bertrand Drouvot <bertranddrouvot.pg@gmail.com> Reviewed-by: Nazir Bilal Yavuz <byavuz81@gmail.com> Discussion: https://postgr.es/m/kgng5nrvnlv335evmsuvpnh354rw7qyazl73kdysev2cr2v5zu@m3cfzxicm5kp
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/.