ef8d8215de
After commit e8b1ad4c2 ("BUG/MEDIUM: clock: also update the date offset
on time jumps"), @firexinghe mentioned that the issue was still present
in their case. In fact it depends on the load, which affects the
probability that the time changes between two poll() calls vs that it
changes during poll(). The time correction code used to only deal with
the latter. But under load if it changes between two poll() calls, what
happens then is that before_poll is off, and after returning from poll(),
the date is within bounds defined by before_poll, so no correction is
applied.
After many tests, it turns out that the most reliable solution without
using CLOCK_MONOTONIC is to prevent before_poll from being earlier than
the previous after_poll (trivial), and to cover forward jumps, we need
to enforce a margin. Given that the watchdog kills a looping task within
2 seconds and that no sane setup triggers it, it seems that 2 seconds
remains a safe enough margin. This means that in the worst case, some
forward jumps of up to 2 seconds will not be corrected, leading to an
apparent fast time and low rates. But this is supposed to be an exceptional
event anyway (typically an admin or crontab running ntpdate).
For future versions, given that we now opportunistically call
now_mono_time() before and after poll(), that returns zero if not
supported, we could imagine relying on this one for the thread's local
time when it's non-null.
HAProxy
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:
- doc/intro.txt for a quick introduction on HAProxy
- doc/configuration.txt for the configuration's reference manual
- doc/lua.txt for the Lua's reference manual
- doc/SPOE.txt for how to use the SPOE engine
- doc/network-namespaces.txt for how to use network namespaces under Linux
- doc/management.txt for the management guide
- doc/regression-testing.txt for how to use the regression testing suite
- doc/peers.txt for the peers protocol reference
- doc/coding-style.txt for how to adopt HAProxy's coding style
- doc/internals for developer-specific documentation (not all up to date)
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.