DOC: opentracing: add the OpenTracing filter section
diff --git a/doc/configuration.txt b/doc/configuration.txt
index e60e342..32df1ca 100644
--- a/doc/configuration.txt
+++ b/doc/configuration.txt
@@ -118,6 +118,7 @@
9.3. Stream Processing Offload Engine (SPOE)
9.4. Cache
9.5. fcgi-app
+9.6. OpenTracing
10. FastCGI applications
10.1. Setup
@@ -20754,6 +20755,40 @@
about the cache filter and section 10 about FastCGI application.
+9.6. OpenTracing
+----------------
+
+The OpenTracing filter adds native support for using distributed tracing in
+HAProxy. This is enabled by sending an OpenTracing compliant request to one
+of the supported tracers such as Datadog, Jaeger, Lightstep and Zipkin tracers.
+Please note: tracers are not listed by any preference, but alphabetically.
+
+This feature is only enabled when haproxy was built with USE_OT=1.
+
+The OpenTracing filter activation is done explicitly by specifying it in the
+HAProxy configuration. If this is not done, the OpenTracing filter in no way
+participates in the work of HAProxy.
+
+filter opentracing [id <id>] config <file>
+
+ Arguments :
+
+ <id> is the OpenTracing filter id that will be used to find the
+ right scope in the configuration file. If no filter id is
+ specified, 'ot-filter' is used as default. If scope is not
+ specified in the configuration file, it applies to all defined
+ OpenTracing filters.
+
+ <file> is the path of the OpenTracing configuration file. The same
+ file can contain configurations for multiple OpenTracing
+ filters simultaneously. In that case we do not need to define
+ scope so the same configuration applies to all filters or each
+ filter must have its own scope defined.
+
+More detailed documentation related to the operation, configuration and use
+of the filter can be found in the contrib/opentracing directory.
+
+
10. FastCGI applications
-------------------------