Fix ocagent trace exporter. (#390)

* Trace/Span IDs need to be binary, not hex encoded.
* Don't set parent_span_id on root spans.

Author: g-easy

opencensus/exporters/trace/ocagent/internal/ocagent_exporter.cc

@@ -208,11 +208,16 @@ void ConvertSpans(
     auto to_span = request->add_spans();
 
     // 1. trace_id
-    to_span->set_trace_id(from_span.context().trace_id().ToHex());
+    to_span->set_trace_id(from_span.context().trace_id().Value(),
+                          ::opencensus::trace::TraceId::kSize);
     // 2. span_id
-    to_span->set_span_id(from_span.context().span_id().ToHex());
+    to_span->set_span_id(from_span.context().span_id().Value(),
+                         ::opencensus::trace::SpanId::kSize);
     // 3. parent_span_id
-    to_span->set_parent_span_id(from_span.parent_span_id().ToHex());
+    if (from_span.parent_span_id().IsValid()) {
+      to_span->set_parent_span_id(from_span.parent_span_id().Value(),
+                                  ::opencensus::trace::SpanId::kSize);
+    }
     // 4. name
     SetTruncatableString(from_span.name(), kDisplayNameStringLen,
                          to_span->mutable_name());
@@ -224,7 +229,7 @@ void ConvertSpans(
     // 7. Export Attributes
     ConvertAttributes(from_span, to_span);
 
-    // 8. stack_trace
+    // 8. stack_trace (unsupported)
 
     // 9. Export Time Events.
     ConvertTimeEvents(from_span, to_span);
@@ -241,7 +246,7 @@ void ConvertSpans(
     to_span->mutable_same_process_as_parent_span()->set_value(
         !from_span.has_remote_parent());
 
-    // 13. child_span_count
+    // 13. child_span_count (optional)
 
     // 14. span kind
 

opencensus/trace/internal/span_id.cc

@@ -30,6 +30,8 @@ std::string SpanId::ToHex() const {
       absl::string_view(reinterpret_cast<const char *>(rep_), kSize));
 }
 
+const void *SpanId::Value() const { return rep_; }
+
 bool SpanId::operator==(const SpanId &that) const {
   return memcmp(rep_, that.rep_, kSize) == 0;
 }

opencensus/trace/internal/trace_id.cc

@@ -30,6 +30,8 @@ std::string TraceId::ToHex() const {
       absl::string_view(reinterpret_cast<const char *>(rep_), kSize));
 }
 
+const void *TraceId::Value() const { return rep_; }
+
 bool TraceId::operator==(const TraceId &that) const {
   return memcmp(rep_, that.rep_, kSize) == 0;
 }

opencensus/trace/span_id.h

@@ -37,6 +37,9 @@ class SpanId final {
   // Returns a 16-char hex string of the SpanId value.
   std::string ToHex() const;
 
+  // Returns a pointer to the opaque value.
+  const void* Value() const;
+
   bool operator==(const SpanId& that) const;
 
   // Returns false if the SpanId is all zeros.

opencensus/trace/trace_id.h

@@ -37,6 +37,9 @@ class TraceId final {
   // Returns a 32-char hex string of the TraceId value.
   std::string ToHex() const;
 
+  // Returns a pointer to the opaque value.
+  const void* Value() const;
+
   bool operator==(const TraceId& that) const;
 
   // Returns false if the TraceId is all zeros.