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Previously, if async notify processing encountered an error, we would report the error to the client and advance our read position past the offending entry to prevent trying to process it over and over again. Trying to continue after an error has a few problems however: - We have no way of telling the client that a notification was lost. They get an ERROR, but that doesn't tell you much. As such, it's not clear if keeping the connection alive after losing a notification is a good thing. Depending on the application logic, missing a notification could cause the application to get stuck waiting, for example. - If the connection is idle, PqCommReadingMsg is set and any ERROR is turned into FATAL anyway. - We bailed out of the notification processing loop on first error without processing any subsequent notifications. The subsequent notifications would not be processed until another notify interrupt arrives. For example, if there were two notifications pending, and processing the first one caused an ERROR, the second notification would not be processed until someone sent a new NOTIFY. This commit changes the behavior so that any ERROR while processing async notifications is turned into FATAL, causing the client connection to be terminated. That makes the behavior more consistent as that's what happened in idle state already, and terminating the connection is a clear signal to the application that it might've missed some notifications. The reason to do this now is that the next commits will change the notification processing code in a way that would make it harder to skip over just the offending notification entry on error. Reviewed-by: Matheus Alcantara <matheusssilv97@gmail.com> Reviewed-by: Álvaro Herrera <alvherre@kurilemu.de> Reviewed-by: Arseniy Mukhin <arseniy.mukhin.dev@gmail.com> Discussion: https://www.postgresql.org/message-id/fedbd908-4571-4bbe-b48e-63bfdcc38f64@iki.fi Backpatch-through: 14
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/.