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Andres Freund 91c40548d5 Fix XLogReader FD leak that makes backends unusable after 2PC usage.
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
2020-04-07 17:03:04 -07:00
config Enable Unix-domain sockets support on Windows 2020-03-28 15:01:01 +01:00
contrib Consider Incremental Sort paths at additional places 2020-04-07 16:43:22 +02:00
doc Allow users to limit storage reserved by replication slots 2020-04-07 18:35:00 -04:00
src Fix XLogReader FD leak that makes backends unusable after 2PC usage. 2020-04-07 17:03:04 -07:00
.dir-locals.el Make Emacs perl-mode indent more like perltidy. 2019-01-13 11:32:31 -08:00
.editorconfig Add .editorconfig 2019-12-18 09:13:13 +01:00
.gitattributes gitattributes: Add new file 2019-11-12 08:13:55 +01:00
.gitignore Support for optimizing and emitting code in LLVM JIT provider. 2018-03-22 11:05:22 -07:00
COPYRIGHT Update copyrights for 2020 2020-01-01 12:21:45 -05:00
GNUmakefile.in Add support for automatically updating Unicode derived files 2020-01-09 10:08:14 +01:00
HISTORY Canonicalize some URLs 2020-02-10 20:47:50 +01:00
Makefile Don't unset MAKEFLAGS in non-GNU Makefile. 2019-06-25 09:36:21 +12:00
README Canonicalize some URLs 2020-02-10 20:47:50 +01:00
README.git Canonicalize some URLs 2020-02-10 20:47:50 +01:00
aclocal.m4 Fix configure's AC_CHECK_DECLS tests to work correctly with clang. 2018-11-19 12:01:47 -05:00
configure Enable Unix-domain sockets support on Windows 2020-03-28 15:01:01 +01:00
configure.in Define EXEC_BACKEND in pg_config_manual.h 2020-03-25 14:31:14 +01:00

README

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/.