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Tom Lane 8b0b6303e9 Try to ensure that stats collector's receive buffer size is at least 100KB. 
Since commit 4e37b3e15, buildfarm member frogmouth has been failing
occasionally with symptoms indicating that some expected stats data is
getting dropped.  The reason that that commit changed the behavior seems
probably to be that more data is getting shoved at the collector in a short
span of time.  In current sources, the stats test's first session sends
about 9KB of data while exiting, which is probably the same as what was
sent just before wait_for_stats() in the previous test design.  But now,
the test's second session is starting up concurrently, and it sends another
2KB (presumably reflecting its initial catalog accesses).  Since frogmouth
is running on Windows XP, which reputedly has a default socket receive
buffer size of only 8KB, it is not very surprising if this has put us over
the threshold where the receive buffer can overflow and drop messages.

The same mechanism could very easily explain the intermittent stats test
failures we've been seeing for years, since background processes such
as the bgwriter will sometimes send data concurrently with all this, and
could thus cause occasional buffer overflows.

Hence, insert some code into pgstat_init() to increase the stats socket's
receive buffer size to 100KB if it's less than that.  (On failure, emit a
LOG message, but keep going.)  Modern systems seem to have default sizes
in the range of 100KB-250KB, but older platforms don't.  I couldn't find
any platforms that wouldn't accept 100KB, so in theory this won't cause
any portability problems.

If this is successful at reducing the buildfarm failure rate in HEAD,
we should back-patch it, because it's certain that similar buffer overflows
happen in the field on platforms with small buffer sizes.  Going forward,
there might be an argument for trying to increase the buffer size even
more, but let's take a baby step first.

Discussion: https://postgr.es/m/22173.1494788088@sss.pgh.pa.us
2017-05-16 15:24:52 -04:00
config Update config.guess and config.sub 2017-05-14 11:09:34 -04:00
contrib Suppress indentation from Data::Dumper in regression tests 2017-05-14 01:10:18 -04:00
doc doc: Remove unnecessary RETURN statements from example. 2017-05-16 11:36:47 -04:00
src Try to ensure that stats collector's receive buffer size is at least 100KB. 2017-05-16 15:24:52 -04:00
.dir-locals.el emacs: Set indent-tabs-mode in perl-mode 2015-04-12 23:53:23 -04:00
.gitattributes Remove contrib/tsearch2. 2017-02-13 11:06:11 -05:00
.gitignore Allow .so minor version numbers above 9 in .gitignore. 2016-08-15 17:35:35 -04:00
aclocal.m4 ICU support 2017-03-23 15:28:48 -04:00
configure Stamp 10beta1. 2017-05-15 17:20:59 -04:00
configure.in Stamp 10beta1. 2017-05-15 17:20:59 -04:00
COPYRIGHT Update copyright for 2017 2017-01-03 12:37:53 -05:00
GNUmakefile.in Have "make coverage" recurse into contrib as well 2016-09-05 18:44:36 -03:00
HISTORY Improve text of stub HISTORY file. 2014-02-12 18:16:17 -05:00
Makefile Allow make check in PL directories 2011-02-15 06:52:12 +02:00
README Don't generate plain-text HISTORY and src/test/regress/README anymore. 2014-02-10 20:48:04 -05:00
README.git Don't generate plain-text HISTORY and src/test/regress/README anymore. 2014-02-10 20:48:04 -05:00

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:

	http://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
http://www.postgresql.org/download/.  For more information look at our
web site located at http://www.postgresql.org/.