Add accessors to deconstruct Span

lib/open_telemetry.ex

@@ -133,7 +133,7 @@ defmodule OpenTelemetry do
   defdelegate link(trace_id, span_id, attributes, tracestate), to: :opentelemetry
 
   @doc """
-  Creates a list of `t:link/0` from a list of 3-tuples.
+  Creates a list of `t:link/0` from a list of 4-tuples.
   """
   @spec links([{integer(), integer(), list(), list()}]) :: [link()]
   defdelegate links(link_list), to: :opentelemetry

lib/open_telemetry/span.ex

@@ -26,6 +26,25 @@ defmodule OpenTelemetry.Span do
   - A Status (`t:OpenTelemetry.status/0`)
   """
 
+  @doc """
+  Get the SpanId of a Span.
+  """
+  @spec span_id(OpenTelemetry.span_ctx()) :: OpenTelemetry.span_id()
+  defdelegate span_id(span), to: :ot_span
+
+  @doc """
+  Get the TraceId of a Span.
+  """
+  @spec trace_id(OpenTelemetry.span_ctx()) :: OpenTelemetry.trace_id()
+  defdelegate trace_id(span), to: :ot_span
+
+  @doc """
+  Get the Tracestate of a Span.
+  """
+  @spec tracestate(OpenTelemetry.span_ctx()) :: OpenTelemetry.tracestate()
+  defdelegate tracestate(span), to: :ot_span
+
+
   @doc """
   Set an attribute with key and value on the currently active Span.
   """

src/ot_span.erl

@@ -19,6 +19,9 @@
 -module(ot_span).
 
 -export([get_ctx/2,
+         trace_id/1,
+         span_id/1,
+         tracestate/1,
          is_recording/2,
          set_attribute/4,
          set_attributes/3,
@@ -126,6 +129,16 @@ update_name(Tracer, SpanCtx, SpanName) when ?is_recording(SpanCtx) ->
 update_name(_, _, _) ->
     false.
 
+%% accessors
+-spec trace_id(opentelemetry:span_ctx()) -> opentelemetry:trace_id().
+trace_id(#span_ctx{ trace_id = TraceId }) -> TraceId.
+
+-spec span_id(opentelemetry:span_ctx()) -> opentelemetry:span_id().
+span_id(#span_ctx{ span_id = SpanId }) -> SpanId.
+
+-spec tracestate(opentelemetry:span_ctx()) -> opentelemetry:tracestate().
+tracestate(#span_ctx{ tracestate = Tracestate }) -> Tracestate.
+
 %% internal functions
 
 do_span_function(Function, Tracer, SpanCtx, Args) ->

test/open_telemetry_test.exs

@@ -32,4 +32,14 @@ defmodule OpenTelemetryTest do
       end
     end
   end
+
+  test "can deconstruct a span context" do
+    Tracer.with_span "span-1" do
+      span = Tracer.current_span_ctx()
+
+      assert nil != Span.trace_id(span)
+      assert nil != Span.span_id(span)
+      assert []   = Span.tracestate(span)
+    end
+  end
 end

test/opentelemetry_api_SUITE.erl

@@ -9,7 +9,7 @@
 -include("tracer.hrl").
 
 all() ->
-    [noop_tracer, update_span_data, noop_with_span, macros].
+    [noop_tracer, update_span_data, noop_with_span, macros, can_create_link_from_span].
 
 init_per_suite(Config) ->
     application:load(opentelemetry_api),
@@ -18,6 +18,30 @@ init_per_suite(Config) ->
 end_per_suite(_Config) ->
     ok.
 
+can_create_link_from_span(_Config) ->
+  %% start a span to create a link to
+  SpanCtx = ?start_span(<<"span-1">>),
+
+  %% extract individual values from span context
+  TraceId = ot_span:trace_id(SpanCtx),
+  SpanId = ot_span:span_id(SpanCtx),
+  Tracestate = ot_span:tracestate(SpanCtx),
+
+  %% end span, so there's no current span set
+  ?end_span(),
+
+  %% we don't need any attributes for this test
+  Attributes = [],
+
+  %% attempt to create a link
+  Link = opentelemetry:link(TraceId, SpanId, Attributes, Tracestate),
+  ?assertMatch(#link{ trace_id = TraceId
+                    , span_id = SpanId
+                    , attributes = Attributes
+                    , tracestate = Tracestate
+                    }, Link).
+
+
 noop_tracer(_Config) ->
     %% start a span and 2 children
     SpanCtx1 = ?start_span(<<"span-1">>),