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HAProxy - Load balancer
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Willy Tarreau f535d3e031 BUG/MEDIUM: debug: only dump Lua state when panicking 
For a long time, we've tried to show the Lua state and backtrace when
dumping threads so as to be able to figure is (and which) Lua code was
misbehaving, e.g. by performing expensive library calls. Since 3.1 with
commit 365ee28510 ("BUG/MINOR: hlua: prevent LJMP in hlua_traceback()"),
it appears that the approach is more fragile (though that fix addressed
a real issue about out-of-memory), and it's possible to occasionally
observe crashes or CPU loops with "show threads" while running Lua
heavily. While users of "show threads" are rare, the watchdog warnings,
which were also enabled on 3.1, also trigger these issues, which is
even more of a concern.

This patch goes the simple way to address this for now: since the purpose
of the Lua backtrace was to help locate Lua call places upon a panic,
let's only call the backtrace on panic but not in other situations. After
a panic we obviously don't care that the Lua stack might be corrupted
since it's never going to be resumed anyway. This may be relaxed in the
future if a solution is found to reliably produce harmless Lua backtraces.

The commit above was backported to all stable branches, so this patch
will be needed everywhere. However, TAINTED_PANIC only appeared in 2.8,
and given the rarety of this bug before 3.1, it's probably not needed
to make any extra effort to go beyond 2.8.

It's easy enough to test a version for being subject to this issue,
by running the following Lua code:

  local function stress(txn)
          for _, backend in pairs(core.backends) do
                  for _, server in pairs(backend.servers) do
                          local stats = server:get_stats()
                  end
          end
  end

  core.register_fetches("stress", stress)

in the following config file:

  global
        stats socket /tmp/haproxy.stat level admin mode 666
        tune.lua.bool-sample-conversion normal
        lua-load-per-thread "stress.lua"

  listen stress
        bind :8001
        mode http
        timeout client 5s
        timeout server 5s
        timeout connect 5s
        http-request return status 200 content-type text/plain lf-string %[lua.stress()]
        server s1 127.0.0.1:8000

and stressing port 8001 with 100+ connections requesting / in loop, then
issuing "show threads" on the CLI using socat in loops as well. Normally
it instantly segfaults (sometimes during the first "show").
2026-01-22 15:47:42 +01:00
.github CI: github: fix vtest.yml with "not quictls" 2026-01-19 13:22:10 +01:00
addons BUG/MEDIUM: promex: server iteration may rely on stale server 2026-01-19 14:24:11 +01:00
admin MEDIUM: systemd: implement directory loading 2026-01-16 09:55:33 +01:00
dev CLEANUP: use the automatic alignment feature 2025-12-09 17:14:58 +01:00
doc DOC: vars: document dump_all_vars() sample fetch 2026-01-21 10:44:19 +01:00
examples MINOR: mailers: warn if mailers are configured but not actually used 2025-06-27 16:41:18 +02:00
include MINOR: vars: store variable names for runtime access 2026-01-21 10:44:19 +01:00
reg-tests REGTESTS: ssl: fix generate-certificates w/ LibreSSL 2026-01-21 16:50:16 +01:00
scripts SCRIPTS: build: enable symbols in AWS-LC builds 2026-01-22 15:25:24 +01:00
src BUG/MEDIUM: debug: only dump Lua state when panicking 2026-01-22 15:47:42 +01:00
tests TESTS: quic: add unit-tests for QUIC TX part 2025-09-08 14:49:03 +02:00
.cirrus.yml CI: cirrus-ci: bump FreeBSD image to 14-3 2025-10-09 14:06:48 +02:00
.gitattributes MINOR: Configure the cpp userdiff driver for *.[ch] in .gitattributes 2021-02-22 18:17:57 +01:00
.gitignore MINOR: tevt/dev: Add term_events tool 2025-01-31 10:41:50 +01:00
.mailmap DOC: update Tim's address in .mailmap 2021-09-16 09:14:14 +02:00
.travis.yml MEDIUM: mworker: remove USE_SYSTEMD requirement for -Ws 2024-11-20 12:07:38 +01:00
BRANCHES DOC: clarify the experimental status for certain features 2025-10-17 18:41:13 +02:00
BSDmakefile BUILD: makefile: commit the tiny FreeBSD makefile stub 2023-05-24 17:17:36 +02:00
CHANGELOG [RELEASE] Released version 3.4-dev2 2026-01-07 11:02:12 +01:00
CONTRIBUTING CLEANUP: assorted typo fixes in the code and comments 2025-04-02 11:12:20 +02:00
INSTALL MINOR: version: mention that it's development again 2025-11-26 16:11:47 +01:00
LICENSE LICENSE: add licence exception for OpenSSL 2012-09-07 13:52:26 +02:00
MAINTAINERS MAJOR: spoe: Let the SPOE back into the game 2024-05-22 09:04:38 +02:00
Makefile REORG: cfgparse: move peers parsing to cfgparse-peers.c 2026-01-20 17:17:37 +01:00
README.md DOC: change the link to the FreeBSD CI in README.md 2024-06-03 15:21:29 +02:00
SUBVERS BUILD: use format tags in VERDATE and SUBVERS files 2013-12-10 11:22:49 +01:00
VERDATE [RELEASE] Released version 3.4-dev2 2026-01-07 11:02:12 +01:00
VERSION [RELEASE] Released version 3.4-dev2 2026-01-07 11:02:12 +01:00

README.md

HAProxy

alpine/musl AWS-LC openssl no-deprecated Illumos NetBSD FreeBSD VTest

HAProxy logo

HAProxy is a free, very fast and reliable reverse-proxy offering high availability, load balancing, and proxying for TCP and HTTP-based applications.

Installation

The INSTALL file describes how to build HAProxy. A list of packages is also available on the wiki.

Getting help

The discourse and the mailing-list are available for questions or configuration assistance. You can also use the slack or IRC channel. Please don't use the issue tracker for these.

The issue tracker is only for bug reports or feature requests.

Documentation

The HAProxy documentation has been split into a number of different files for ease of use. It is available in text format as well as HTML. The wiki is also meant to replace the old architecture guide.

Please refer to the following files depending on what you're looking for:

  • INSTALL for instructions on how to build and install HAProxy
  • BRANCHES to understand the project's life cycle and what version to use
  • LICENSE for the project's license
  • CONTRIBUTING for the process to follow to submit contributions

The more detailed documentation is located into the doc/ directory:

License

HAProxy is licensed under GPL 2 or any later version, the headers under LGPL 2.1. See the LICENSE file for a more detailed explanation.