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Before the fix every 2PC commit/abort leaked a file descriptor. As the files are opened using BasicOpenFile(), that quickly leads to the backend running out of file descriptors. Once enough 2PC abort/commit have caused enough FDs to leak, any IO in the backend will fail with "Too many open files", as BasicOpenFilePerm() will have triggered all open files known to fd.c to be closed. The leak causing the problem at hand is a consequence of 0dc8ead46, but is only exascerbated by it. Previously most XLogPageReadCB callbacks used static variables to cache one open file, but after the commit the cache is private to each XLogReader instance. There never was infrastructure to close FDs at the time of XLogReaderFree, but the way XLogReader was used limited the leak to one FD. This commit just closes the during XLogReaderFree() if the FD is stored in XLogReaderState.seg.ws_segno. This may not be the way to solve this medium/long term, but at least unbreaks 2PC. Discussion: https://postgr.es/m/20200406025651.fpzdb5yyb7qyhqko@alap3.anarazel.de
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/.