README.md in freddy-jruby-1.0.0 vs README.md in freddy-jruby-1.3.2

@@ -133,9 +133,44 @@
   * stop responding
 ```ruby
 responder_handler.shutdown
 ```
 
+## Request Tracing
+
+Freddy supports [OpenTracing API|https://github.com/opentracing/opentracing-ruby]. You must set a global tracer which then freddy will use:
+```ruby
+OpenTracing.global_tracing = MyTracerImplementation.new(...)
+```
+
+For example you can use [Logasm::Tracer](https://github.com/salemove/logasm-tracer) which will log all incoming and outgoing requests with trace ID, parent ID and span ID.
+
+Current trace can be accessed through a thread-local variable `Freddy.trace`. Calling `deliver` or `deliver_with_response` will pass trace context to down-stream services.
+
+Accessing trace information when using Logasm::Tracer implementation:
+
+```ruby
+freddy1 = Freddy.build
+freddy1.respond_do('service1') do |payload, msg_handler|
+  puts "Trace id: #{Freddy.trace.context.trace_id}"
+  puts "Span id: #{Freddy.trace.context.span_id}"
+
+  freddy1.deliver('service2', {})
+end
+
+freddy2 = Freddy.build
+freddy2.tap_into('service2') do |payload|
+  puts "Has same trace_id as the request in service1: #{Freddy.trace.context.trace_id}"
+  puts "Has service1 request span id as parent id: #{Freddy.trace.context.parent_id}"
+  puts "Has its own generated span id: #{Freddy.trace.context.span_id}"
+end
+```
+
+In case you already have an ongoing OpenTracing span (e.g. provided by REST API) then you can pass the trace information to Freddy by doing:
+```ruby
+  Freddy.trace = trace_span
+```
+The `trace_span` must implement OpenTracing::Span interface.
 
 ## Notes about concurrency
 
 *freddy* uses a thread pool to run concurrent responders. The thread pool is unique for each *tap_into* and *respond_to* responder. Thread pool size can be configured by passing the configuration option *max_concurrency*. Its default value is 4. e.g. If your application has 2 *respond_to* responders and 1 *tap_into* responder with *max_concurrency* set to 3 then your application may process up to 9 messages in parallel.