Support W3C headers

lib/lightstep/span.rb

@@ -56,8 +56,9 @@ def initialize(
       ref = ref.context if (Span === ref)
 
       if SpanContext === ref
-        @context = SpanContext.new(id: LightStep.guid, trace_id: ref.trace_id)
+        @context = SpanContext.new(id: LightStep.guid, trace_id: ref.trace_id, trace_state: ref.trace_state)
         set_baggage(ref.baggage)
+
         set_tag(:parent_span_guid, ref.id)
       else
         @context = SpanContext.new(id: LightStep.guid, trace_id: LightStep.guid)
@@ -83,7 +84,8 @@ def set_baggage_item(key, value)
       @context = SpanContext.new(
         id: context.id,
         trace_id: context.trace_id,
-        baggage: context.baggage.merge({key => value})
+        baggage: context.baggage.merge({key => value}),
+        trace_state: context.trace_state
       )
       self
     end
@@ -94,7 +96,8 @@ def set_baggage(baggage = {})
       @context = SpanContext.new(
         id: context.id,
         trace_id: context.trace_id,
-        baggage: baggage
+        baggage: baggage,
+        trace_state: context.trace_state
       )
     end
 
@@ -155,7 +158,7 @@ def to_h
       {
         runtime_guid: tracer.guid,
         span_guid: context.id,
-        trace_guid: context.trace_id,
+        trace_guid: context.trace_id[-16..-1] || context.trace_id, # Hack to ensure the reported ID is <= 16 bytes
         span_name: operation_name,
         attributes: tags.map {|key, value|
           {Key: key.to_s, Value: value}

lib/lightstep/span_context.rb

@@ -1,12 +1,13 @@
 module LightStep
   # SpanContext holds the data for a span that gets inherited to child spans
   class SpanContext
-    attr_reader :id, :trace_id, :baggage
+    attr_reader :id, :trace_id, :baggage, :trace_state
 
-    def initialize(id:, trace_id:, baggage: {})
+    def initialize(id:, trace_id:, baggage: {}, trace_state: [])
       @id = id.freeze
       @trace_id = trace_id.freeze
       @baggage = baggage.freeze
+      @trace_state = trace_state.freeze
     end
   end
 end

lib/lightstep/tracer.rb

@@ -1,4 +1,5 @@
 require 'json'
+require 'base64'
 require 'concurrent'
 
 require 'opentracing'
@@ -262,6 +263,14 @@ def configure(component_name:, access_token: nil, transport: nil, tags: {})
     DEFAULT_MAX_SPAN_RECORDS = 1000
     MIN_MAX_SPAN_RECORDS = 1
 
+    TRACE_PARENT = 'traceparent'.freeze
+    TRACE_PARENT_VERSION = 0
+    TRACE_PARENT_REGEX = /\h{2}-(\h{32})-(\h{16})-\h{2}/
+
+    TRACE_STATE = 'tracestate'.freeze
+    TRACE_STATE_VENDOR = 'lightstep'.freeze
+    MAX_TRACE_STATE_SIZE = 512
+
     def inject_to_text_map(span_context, carrier)
       carrier[CARRIER_SPAN_ID] = span_context.id
       carrier[CARRIER_TRACE_ID] = span_context.trace_id unless span_context.trace_id.nil?
@@ -273,9 +282,20 @@ def inject_to_text_map(span_context, carrier)
     end
 
     def extract_from_text_map(carrier)
+      trace_id = carrier[CARRIER_TRACE_ID]
+      id = carrier[CARRIER_SPAN_ID]
+
+      if trace_id.nil? || trace_id.empty? || id.nil? || id.empty?
+        matches = TRACE_PARENT_REGEX.match(carrier[TRACE_PARENT])
+        unless matches.nil?
+          trace_id = matches[1]
+          id = matches[2]
+        end
+      end
+
       # If the carrier does not have both the span_id and trace_id key
       # skip the processing and just return a normal span
-      if !carrier.has_key?(CARRIER_SPAN_ID) || !carrier.has_key?(CARRIER_TRACE_ID)
+      if trace_id.nil? || trace_id.empty? || id.nil? || id.empty?
         return nil
       end
 
@@ -287,35 +307,84 @@ def extract_from_text_map(carrier)
         end
         baggage
       end
+
+      trace_state = (carrier[TRACE_STATE] || '').split(',')
+        .map { |item| item.match(/^(.*)=(.*)$/).captures }
+        .find_all { |vendor, state| !vendor.nil? && !vendor.empty? && !state.nil? }
+        .reduce([]) do |memo, (vendor, value)|
+          if vendor == TRACE_STATE_VENDOR
+            baggage = baggage.merge(decode_tracestate_baggage(value))
+          else
+            memo << "#{vendor}=#{value}"
+          end
+
+          memo
+        end
+
       SpanContext.new(
-        id: carrier[CARRIER_SPAN_ID],
-        trace_id: carrier[CARRIER_TRACE_ID],
+        id: id,
+        trace_id: trace_id,
         baggage: baggage,
+        trace_state: trace_state
       )
     end
 
     def inject_to_rack(span_context, carrier)
       carrier[CARRIER_SPAN_ID] = span_context.id
       carrier[CARRIER_TRACE_ID] = span_context.trace_id unless span_context.trace_id.nil?
       carrier[CARRIER_SAMPLED] = 'true'
+      carrier[TRACE_PARENT] = format('%<version>02x-%<trace_id>s-%<span_id>s-01', {
+        version: TRACE_PARENT_VERSION,
+        trace_id: span_context.trace_id.rjust(32, '0'),
+        span_id: span_context.id.rjust(16, '0')
+      })
 
-      span_context.baggage.each do |key, value|
+      span_context.baggage.sort.each do |key, value|
         if key =~ /[^A-Za-z0-9\-_]/
           # TODO: log the error internally
           next
         end
+
         carrier[CARRIER_BAGGAGE_PREFIX + key] = value
       end
+
+      encoded_baggage = ''
+
+      unless span_context.baggage.empty?
+        encoded_baggage = Base64.urlsafe_encode64(JSON.generate(span_context.baggage), padding: false)
+      end
+
+      trace_state = "#{TRACE_STATE_VENDOR}=#{encoded_baggage}"
+
+      for item in span_context.trace_state
+        if trace_state.length + item.length + 1 > MAX_TRACE_STATE_SIZE
+          break
+        end
+
+        trace_state << ',' << item
+      end
+
+      carrier[TRACE_STATE] = trace_state
     end
 
     def extract_from_rack(env)
       extract_from_text_map(env.reduce({}){|memo, tuple|
         raw_header, value = tuple
-        header = raw_header.gsub(/^HTTP_/, '').tr('_', '-').downcase
+        header = raw_header.to_s.gsub(/^HTTP_/, '').tr('_', '-').downcase
 
-        memo[header] = value if header.start_with?(CARRIER_TRACER_STATE_PREFIX, CARRIER_BAGGAGE_PREFIX)
+        memo[header] = value if header.start_with?(CARRIER_TRACER_STATE_PREFIX, CARRIER_BAGGAGE_PREFIX) || header == TRACE_PARENT || header == TRACE_STATE
         memo
       })
     end
+
+    def decode_tracestate_baggage(value)
+      begin
+        decoded_baggage = Base64.urlsafe_decode64(value || '')
+      rescue ArgumentError
+        decoded_baggage = nil
+      end
+
+      JSON.parse(decoded_baggage)
+    end
   end
 end