071ae8ce3d
If a server A is deleted while a stats dump is currently on it, deletion is delayed thanks to reference counting. Server A is nonetheless removed from the proxy list. However, this list is a single linked list. If the next server B is deleted and freed immediately, server A would still point to it. This problem has been solved by the prev_deleted list in servers. This model seems correct, but it is difficult to ensure completely its validity. In particular, it implies when stats dump is resumed, server A elements will be accessed despite the server being in a half-deleted state. Thus, it has been decided to completely ditch the refcount mechanism for stats dump. Instead, use the watcher element to register every stats dump currently tracking a server instance. Each time a server is deleted on the CLI, each stats dump element which may points to it are updated to access the next server instance, or NULL if this is the last server. This ensures that a server which was deleted via CLI but not completely freed is never accessed on stats dump resumption. Currently, no race condition related to dynamic servers and stats dump is known. However, as described above, the previous model is deemed too fragile, as such this patch is labelled as bug-fix. It should be backported up to 2.6, after a reasonable period of observation. It relies on the following patch : MINOR: list: define a watcher type
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.