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Michael Paquier d86d20f0ba Add backend support for injection points
Injection points are a new facility that makes possible for developers
to run custom code in pre-defined code paths.  Its goal is to provide
ways to design and run advanced tests, for cases like:
- Race conditions, where processes need to do actions in a controlled
ordered manner.
- Forcing a state, like an ERROR, FATAL or even PANIC for OOM, to force
recovery, etc.
- Arbitrary sleeps.

This implements some basics, and there are plans to extend it more in
the future depending on what's required.  Hence, this commit adds a set
of routines in the backend that allows developers to attach, detach and
run injection points:
- A code path calling an injection point can be declared with the macro
INJECTION_POINT(name).
- InjectionPointAttach() and InjectionPointDetach() to respectively
attach and detach a callback to/from an injection point.  An injection
point name is registered in a shmem hash table with a library name and a
function name, which will be used to load the callback attached to an
injection point when its code path is run.

Injection point names are just strings, so as an injection point can be
declared and run by out-of-core extensions and modules, with callbacks
defined in external libraries.

This facility is hidden behind a dedicated switch for ./configure and
meson, disabled by default.

Note that backends use a local cache to store callbacks already loaded,
cleaning up their cache if a callback has found to be removed on a
best-effort basis.  This could be refined further but any tests but what
we have here was fine with the tests I've written while implementing
these backend APIs.

Author: Michael Paquier, with doc suggestions from Ashutosh Bapat.
Reviewed-by: Ashutosh Bapat, Nathan Bossart, Álvaro Herrera, Dilip
Kumar, Amul Sul, Nazir Bilal Yavuz
Discussion: https://postgr.es/m/ZTiV8tn_MIb_H2rE@paquier.xyz
2024-01-22 10:15:50 +09:00
config Add copyright notices to a few perl scripts that don't have them 2024-01-05 13:15:50 +00:00
contrib Teach autoprewarm to use the dynamic shared memory registry. 2024-01-19 14:43:59 -06:00
doc Add backend support for injection points 2024-01-22 10:15:50 +09:00
src Add backend support for injection points 2024-01-22 10:15:50 +09:00
.cirrus.star Remove duplicate words in docs and code comments. 2023-10-09 09:18:47 +05:30
.cirrus.tasks.yml Use "template" data directory in tests 2023-08-24 14:38:02 -07:00
.cirrus.yml ci: Make compute resources for CI configurable 2023-08-23 15:15:28 -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
.git-blame-ignore-revs Add previous commit to .git-blame-ignore-revs. 2024-01-13 13:56:46 -05:00
.gitattributes Replace Gen_dummy_probes.sed with Gen_dummy_probes.pl 2023-11-14 10:27:10 +01:00
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COPYRIGHT Update copyright for 2024 2024-01-03 20:49:05 -05:00
GNUmakefile.in Stop generating plain-text INSTALL instructions. 2023-12-22 13:32:15 -05:00
HISTORY Canonicalize some URLs 2020-02-10 20:47:50 +01:00
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README Stop generating plain-text INSTALL instructions. 2023-12-22 13:32:15 -05:00
aclocal.m4 autoconf: Move export_dynamic determination to configure 2022-12-06 18:55:28 -08:00
configure Add backend support for injection points 2024-01-22 10:15:50 +09:00
configure.ac Add backend support for injection points 2024-01-22 10:15:50 +09:00
meson.build Add backend support for injection points 2024-01-22 10:15:50 +09:00
meson_options.txt Add backend support for injection points 2024-01-22 10:15:50 +09:00

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.

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/.