2d6a15ac00
Added support for storing OTel span context in HAProxy transaction variables as an alternative to HTTP headers, enabled by the OTEL_USE_VARS compile flag. The new vars.c module implements variable-based context propagation through the HAProxy variable subsystem. Variable names are constructed from a configurable prefix and the OTel propagation key, with dots normalized to underscores for HAProxy variable name compatibility and denormalized back during retrieval. The module provides flt_otel_var_register() to pre-register variables at parse time, flt_otel_var_set() and flt_otel_vars_unset() to store and clear context key-value pairs in the txn scope, flt_otel_vars_get() to collect all variables matching a prefix into an otelc_text_map for context extraction, and flt_otel_vars_dump() for debug logging of all OTel variables. The inject/extract keywords in the scope parser now accept an optional "use-vars" argument alongside "use-headers", controlled by the new FLT_OTEL_CTX_USE_VARS flag. Both storage types can be used simultaneously on the same span context, allowing context to be propagated through both HTTP headers and variables. The scope runner in event.c was extended to handle variable-based context in parallel with headers: during extraction, it reads matching variables via flt_otel_vars_get() when FLT_OTEL_CTX_USE_VARS is set; during injection, it stores each propagation key as a variable via flt_otel_var_set(). The unused resource cleanup now also unsets context variables when removing failed extraction contexts. The filter attach callback registers and sets the sess.otel.uuid variable with the generated session UUID, making the trace identifier available to HAProxy log formats and ACL expressions. The feature is conditionally compiled: the OTEL_USE_VARS flag controls whether vars.c is included in the build and whether the "use-vars" keyword is available in the configuration parser.
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.