4319c20363
We no longer rely on now_offset stored in the shm-stats-file. Instead
haproxy automatically computes the now_offset relative to the monotonic
clock and the shared global clock.
Indeed, the previous model based on static now_offset when monotonic
clock is available proved to be insufficient when used in
combination with shm-stats-file (that is when monotonic clock is shared
between multiple co-processes). In ideal situation co-processes would
correctly apply the offset to their local monotonic clock and end up
with consistent now_ns. But when restarting from an existing
shm-stats-file from a previous session (ie: prior to reboot), then the
local monotonic clock would no longer be consistent with the one used
to update the file previously, so applying a static offset would fail
to restore clock consistency.
For this specific issue, a workaround was brought by 09bf116
("BUG/MEDIUM: stats-file: detect and fix inconsistent shared clock when resuming from shm-stats-file")
but the solution implemented there was deemed too fragile, because there
is a 60sec window where the fix would fail to detect inconsistent clock
and would leave haproxy with a broken clock ranging from 0 to 60 seconds,
which can be huge..
By simply recomputing the now_offset each time we learn from another
process (through the shared map by reading global_now_ns), we simply
recompute our local offset (difference between OUR monotonic clock
and the SHARED one). Also, in clock_update_global_date(), we make
sure we always recompute the now_offset as now_ms may have been
updated from shared clock if shared clock was ahead of us.
Thanks to that new logic, interrupted processes, resumed processes,
processed started with shm-stats-file from previous session now
correctly recover from those various situations and multiple
co-processes with diverting clocks on startup end up converging to
the same values.
Since it is no longer relevant to save now_offset in the map, it was
removed but to prevent shm-stats-file incompatibility with previous
versions, 8-byte hole was forced, and we didn't bump the shm-stats-file
version on purpose.
This patch may be backported in 3.3 after a solid period of observation
to ensure we didn't break things.
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.