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Willy Tarreau 4e65fc66f6 MAJOR: import: update mt_list to support exponential back-off (try #2) 
This is the second attempt at importing the updated mt_list code (commit
59459ea3). The previous one was attempted with commit c618ed5ff4 ("MAJOR:
import: update mt_list to support exponential back-off") but revealed
problems with QUIC connections and was reverted.

The problem that was faced was that elements deleted inside an iterator
were no longer reset, and that if they were to be recycled in this form,
they could appear as busy to the next user. This was trivially reproduced
with this:

  $ cat quic-repro.cfg
  global
          stats socket /tmp/sock1 level admin
          stats timeout 1h
          limited-quic

  frontend stats
          mode http
          bind quic4@:8443 ssl crt rsa+dh2048.pem alpn h3
          timeout client 5s
          stats uri /

  $ ./haproxy -db -f quic-repro.cfg  &

  $ h2load -c 10 -n 100000 --npn h3 https://127.0.0.1:8443/
  => hang

This was purely an API issue caused by the simplified usage of the macros
for the iterator. The original version had two backups (one full element
and one pointer) that the user had to take care of, while the new one only
uses one that is transparent for the user. But during removal, the element
still has to be unlocked if it's going to be reused.

All of this sparked discussions with Fred and Aurélien regarding the still
unclear state of locking. It was found that the lock API does too much at
once and is lacking granularity. The new version offers a much more fine-
grained control allowing to selectively lock/unlock an element, a link,
the rest of the list etc.

It was also found that plenty of places just want to free the current
element, or delete it to do anything with it, hence don't need to reset
its pointers (e.g. event_hdl). Finally it appeared obvious that the
root cause of the problem was the unclear usage of the list iterators
themselves because one does not necessarily expect the element to be
presented locked when not needed, which makes the unlock easy to overlook
during reviews.

The updated version of the list presents explicit lock status in the
macro name (_LOCKED or _UNLOCKED suffixes). When using the _LOCKED
suffix, the caller is expected to unlock the element if it intends to
reuse it. At least the status is advertised. The _UNLOCKED variant,
instead, always unlocks it before starting the loop block. This means
it's not necessary to think about unlocking it, though it's obviously
not usable with everything. A few _UNLOCKED were used at obvious places
(i.e. where the element is deleted and freed without any prior check).

Interestingly, the tests performed last year on QUIC forwarding, that
resulted in limited traffic for the original version and higher bit
rate for the new one couldn't be reproduced because since then the QUIC
stack has gaind in efficiency, and the 100 Gbps barrier is now reached
with or without the mt_list update. However the unit tests definitely
show a huge difference, particularly on EPYC platforms where the EBO
provides tremendous CPU savings.

Overall, the following changes are visible from the application code:

  - mt_list_for_each_entry_safe() + 1 back elem + 1 back ptr
    => MT_LIST_FOR_EACH_ENTRY_LOCKED() or MT_LIST_FOR_EACH_ENTRY_UNLOCKED()
       + 1 back elem

  - MT_LIST_DELETE_SAFE() no longer needed in MT_LIST_FOR_EACH_ENTRY_UNLOCKED()
      => just manually set iterator to NULL however.
    For MT_LIST_FOR_EACH_ENTRY_LOCKED()
      => mt_list_unlock_self() (if element going to be reused) + NULL

  - MT_LIST_LOCK_ELT => mt_list_lock_full()
  - MT_LIST_UNLOCK_ELT => mt_list_unlock_full()

  - l = MT_LIST_APPEND_LOCKED(h, e);  MT_LIST_UNLOCK_ELT();
    => l=mt_list_lock_prev(h); mt_list_lock_elem(e); mt_list_unlock_full(e, l)
 		2024-07-09 16:46:38 +02:00
.github CI: add weekly QUIC Interop regression against LibreSSL 2024-07-05 15:11:21 +02:00
addons BUG/MINOR: promex: Remove Help prefix repeated twice for each metric 2024-07-01 10:50:27 +02:00
admin ADMIN: acme.sh: remove the old acme.sh code 2024-05-31 13:37:47 +02:00
dev DEV: flags/quic: decode quic_conn flags 2024-07-08 09:38:35 +02:00
doc MAJOR: import: update mt_list to support exponential back-off (try #2) 2024-07-09 16:46:38 +02:00
examples CLEANUP: assorted typo fixes in the code and comments 2023-11-23 16:23:14 +01:00
include MAJOR: import: update mt_list to support exponential back-off (try #2) 2024-07-09 16:46:38 +02:00
reg-tests REGTESTS: ssl: activate new SSL reg-tests with AWS-LC 2024-06-17 17:43:22 +02:00
scripts SCRIPTS: git-show-backports: do not truncate git-show output 2024-06-21 15:08:42 +02:00
src MAJOR: import: update mt_list to support exponential back-off (try #2) 2024-07-09 16:46:38 +02:00
tests MAJOR: import: update mt_list to support exponential back-off (try #2) 2024-07-09 16:46:38 +02:00
.cirrus.yml CI: FreeBSD: upgrade image, packages 2024-06-04 11:19:00 +02:00
.gitattributes MINOR: Configure the `cpp` userdiff driver for *.[ch] in .gitattributes 2021-02-22 18:17:57 +01:00
.gitignore CONTRIB: Add vi file extensions to .gitignore 2023-06-02 18:14:34 +02:00
.mailmap DOC: update Tim's address in .mailmap 2021-09-16 09:14:14 +02:00
.travis.yml CI: travis-ci: temporarily disable arm64 builds 2021-08-07 07:28:15 +02:00
BRANCHES DOC: fix some spelling issues over multiple files 2021-01-08 14:53:47 +01:00
BSDmakefile BUILD: makefile: commit the tiny FreeBSD makefile stub 2023-05-24 17:17:36 +02:00
CHANGELOG [RELEASE] Released version 3.1-dev2 2024-06-29 11:28:41 +02:00
CONTRIBUTING CLEANUP: assorted typo fixes in the code and comments 2021-08-16 12:37:59 +02:00
INSTALL DOC: INSTALL: minimum AWS-LC version is v1.22.0 2024-06-14 12:06:03 +02:00
LICENSE
…
MAINTAINERS MAJOR: spoe: Let the SPOE back into the game 2024-05-22 09:04:38 +02:00
Makefile REORG: ssl: move the SNI selection code in ssl_clienthello.c 2024-06-13 16:48:17 +02:00
README.md DOC: change the link to the FreeBSD CI in README.md 2024-06-03 15:21:29 +02:00
SUBVERS
…
VERDATE [RELEASE] Released version 3.1-dev2 2024-06-29 11:28:41 +02:00
VERSION [RELEASE] Released version 3.1-dev2 2024-06-29 11:28:41 +02:00

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.