f535d3e031
For a long time, we've tried to show the Lua state and backtrace when
dumping threads so as to be able to figure is (and which) Lua code was
misbehaving, e.g. by performing expensive library calls. Since 3.1 with
commit 365ee28510 ("BUG/MINOR: hlua: prevent LJMP in hlua_traceback()"),
it appears that the approach is more fragile (though that fix addressed
a real issue about out-of-memory), and it's possible to occasionally
observe crashes or CPU loops with "show threads" while running Lua
heavily. While users of "show threads" are rare, the watchdog warnings,
which were also enabled on 3.1, also trigger these issues, which is
even more of a concern.
This patch goes the simple way to address this for now: since the purpose
of the Lua backtrace was to help locate Lua call places upon a panic,
let's only call the backtrace on panic but not in other situations. After
a panic we obviously don't care that the Lua stack might be corrupted
since it's never going to be resumed anyway. This may be relaxed in the
future if a solution is found to reliably produce harmless Lua backtraces.
The commit above was backported to all stable branches, so this patch
will be needed everywhere. However, TAINTED_PANIC only appeared in 2.8,
and given the rarety of this bug before 3.1, it's probably not needed
to make any extra effort to go beyond 2.8.
It's easy enough to test a version for being subject to this issue,
by running the following Lua code:
local function stress(txn)
for _, backend in pairs(core.backends) do
for _, server in pairs(backend.servers) do
local stats = server:get_stats()
end
end
end
core.register_fetches("stress", stress)
in the following config file:
global
stats socket /tmp/haproxy.stat level admin mode 666
tune.lua.bool-sample-conversion normal
lua-load-per-thread "stress.lua"
listen stress
bind :8001
mode http
timeout client 5s
timeout server 5s
timeout connect 5s
http-request return status 200 content-type text/plain lf-string %[lua.stress()]
server s1 127.0.0.1:8000
and stressing port 8001 with 100+ connections requesting / in loop, then
issuing "show threads" on the CLI using socat in loops as well. Normally
it instantly segfaults (sometimes during the first "show").
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.