8f28dbeea9
When a resolver is woken up to process DNS resolutions, it is possible to trigger an infinite loop on the resolver's wait list because delayed resolutions are always reinserted at the end of this list. This leads the watchdog to kill the process. By re-inserting them in front of the list, that fixes the bug. When a resolver tries to send the queries for the resolutions in its wait list, it may be unable to proceed for a resolution. This may happen because the resolution must be skipped (no hostname to resolv, a resolution already in-progress) or when an error occurred. In that case, the resolution is re-inserted in the resolver's wait list to be retry later, on a next wakeup. However, the resolution is inserted at the end of the wait list. So it is immediately reevaluated, in the same execution loop, instead of to be delayed. Most of time, it is not an issue because the resolution is considered as not expired on the second run. But it is an problem when the internal time wraps and is equal to 0. In that case, the resolution expiration date is badly computed and it is always considered as expired. If two or more resolutions are in that state, the resolver loops for ever on its wait list, until the process is killed by the watchdog. So we can argue that the way the resolution expiration date is computed must be fixed. And it would be true in a perfect world. However, the resolvers code is so crapy that it is hard to be sure to not introduce regressions. It is farly easier to re-insert delayed resolutions in front of the wait list. This fixes the issue and at worst, these resolutions will be evaluated one time too many on the next wakeup and only if now_ms was equal to 0 on the prior wakeup. This patch should be backported to all stable versions. On 2.2, LIST_ADD() must be used instead of LIST_INSERT() |
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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.