untested: propagation style order matters

Author: dgoffredo

BUILD.bazel

@@ -26,7 +26,7 @@ cc_library(
     "src/datadog/null_collector.cpp",
     "src/datadog/optional.cpp",
     "src/datadog/parse_util.cpp",
-    "src/datadog/propagation_styles.cpp",
+    "src/datadog/propagation_style.cpp",
     "src/datadog/rate.cpp",
     "src/datadog/sampling_decision.cpp",
     "src/datadog/sampling_mechanism.cpp",
@@ -77,7 +77,7 @@ cc_library(
     "src/datadog/null_collector.h",
     "src/datadog/optional.h",
     "src/datadog/parse_util.h",
-    "src/datadog/propagation_styles.h",
+    "src/datadog/propagation_style.h",
     "src/datadog/rate.h",
     "src/datadog/sampling_decision.h",
     "src/datadog/sampling_mechanism.h",

CMakeLists.txt

@@ -6,6 +6,8 @@ project(dd-trace-cpp)
 
 option(BUILD_COVERAGE "Build code with code coverage profiling instrumentation" OFF)
 option(BUILD_EXAMPLE "Build the example program (example/)" OFF)
+option(BUILD_TESTING "Build the unit tests (test/)" OFF)
+option(SANITIZE "Build with address sanitizer and undefined behavior sanitizer" OFF)
 
 set(CMAKE_BUILD_TYPE "RelWithDebInfo")
 set(CMAKE_POSITION_INDEPENDENT_CODE ON)
@@ -78,7 +80,7 @@ target_sources(dd_trace_cpp PRIVATE
     src/datadog/null_collector.cpp
     src/datadog/optional.cpp
     src/datadog/parse_util.cpp
-    src/datadog/propagation_styles.cpp
+    src/datadog/propagation_style.cpp
     src/datadog/rate.cpp
     src/datadog/sampling_decision.cpp
     src/datadog/sampling_mechanism.cpp
@@ -135,7 +137,7 @@ target_sources(dd_trace_cpp PUBLIC
   src/datadog/null_collector.h
   src/datadog/optional.h
   src/datadog/parse_util.h
-  src/datadog/propagation_styles.h
+  src/datadog/propagation_style.h
   src/datadog/rate.h
   src/datadog/sampling_decision.h
   src/datadog/sampling_mechanism.h

doc/includes.dot

@@ -75,7 +75,7 @@ digraph G {
 	node73 [label="version.cpp"];
 	node74 [label="span_matcher.h"];
 	node75 [label="span_sampler_config.h"];
-	node76 [label="propagation_styles.cpp"];
+	node76 [label="propagation_style.cpp"];
 	node77 [label="dict_reader.h"];
 	node78 [label="span_matcher.cpp"];
 	node79 [label="default_http_client_curl.cpp"];
@@ -84,7 +84,7 @@ digraph G {
 	node82 [label="clock.cpp"];
 	node83 [label="collector_response.cpp"];
 	node84 [label="sampling_priority.h"];
-	node85 [label="propagation_styles.h"];
+	node85 [label="propagation_style.h"];
 	node86 [label="limiter.cpp"];
 	node87 [label="net_util.h"];
 	node88 [label="error.cpp"];

doc/includes.svg

@@ -68,6 +68,7 @@ struct Error {
     MISSING_TRACE_ID = 43,
     ENVOY_HTTP_CLIENT_FAILURE = 44,
     MULTIPLE_PROPAGATION_STYLE_ENVIRONMENT_VARIABLES = 45,
+    DUPLICATE_PROPAGATION_STYLE = 46,
   };
 
   Code code;

src/datadog/error.h

@@ -0,0 +1,31 @@
+#include "propagation_style.h"
+
+#include <cassert>
+
+#include "json.hpp"
+
+namespace datadog {
+namespace tracing {
+
+nlohmann::json to_json(PropagationStyle style) {
+  switch (style) {
+    case PropagationStyle::DATADOG:
+      return "datadog";
+    case PropagationStyle::B3:
+      return "B3";
+    default:
+      assert(style == PropagationStyle::NONE);
+      return "none";
+  }
+}
+
+nlohmann::json to_json(const std::vector<PropagationStyle>& styles) {
+  std::vector<nlohmann::json> styles_json;
+  for (const auto style : styles) {
+    styles_json.push_back(to_json(style));
+  }
+  return styles_json;
+}
+
+}  // namespace tracing
+}  // namespace datadog

src/datadog/propagation_style.cpp

@@ -0,0 +1,30 @@
+#pragma once
+
+// This component provides an `enum class`, `PropagationStyle`, that indicates a
+// trace context extraction or injection format to be used. `TracerConfig` has
+// one `std::vector<PropagationStyle>` for extraction and another for injection.
+// See `tracer_config.h`.
+
+#include <vector>
+
+#include "json_fwd.hpp"
+
+namespace datadog {
+namespace tracing {
+
+enum class PropagationStyle {
+  // Datadog headers, e.g. X-Datadog-Trace-ID
+  DATADOG,
+  // B3 multi-header style, e.g. X-B3-TraceID
+  B3,
+  // The absence of propagation.  If this is the only style set, then
+  // propagation is disabled in the relevant direction (extraction or
+  // injection).
+  NONE,
+};
+
+nlohmann::json to_json(PropagationStyle style);
+nlohmann::json to_json(const std::vector<PropagationStyle>& styles);
+
+}  // namespace tracing
+}  // namespace datadog

src/datadog/propagation_style.h

@@ -45,7 +45,7 @@ TraceSegment::TraceSegment(
     const std::shared_ptr<TraceSampler>& trace_sampler,
     const std::shared_ptr<SpanSampler>& span_sampler,
     const std::shared_ptr<const SpanDefaults>& defaults,
-    const PropagationStyles& injection_styles,
+    const std::vector<PropagationStyle>& injection_styles,
     const Optional<std::string>& hostname, Optional<std::string> origin,
     std::size_t tags_header_max_size,
     std::unordered_map<std::string, std::string> trace_tags,
@@ -224,8 +224,8 @@ void TraceSegment::inject(DictWriter& writer, const SpanData& span) {
   // Origin and trace tag headers are always propagated, unless the only
   // injection style is "none".
   // Other headers depend on the injection styles.
-  if (injection_styles_.none && !injection_styles_.datadog &&
-      !injection_styles_.b3) {
+  if (injection_styles_.size() == 1 &&
+      injection_styles_[0] == PropagationStyle::NONE) {
     return;
   }
 
@@ -248,17 +248,22 @@ void TraceSegment::inject(DictWriter& writer, const SpanData& span) {
     writer.set("x-datadog-tags", encoded_trace_tags);
   }
 
-  if (injection_styles_.datadog) {
-    writer.set("x-datadog-trace-id", std::to_string(span.trace_id));
-    writer.set("x-datadog-parent-id", std::to_string(span.span_id));
-    writer.set("x-datadog-sampling-priority",
-               std::to_string(sampling_priority));
-  }
-
-  if (injection_styles_.b3) {
-    writer.set("x-b3-traceid", hex(span.trace_id));
-    writer.set("x-b3-spanid", hex(span.span_id));
-    writer.set("x-b3-sampled", std::to_string(int(sampling_priority > 0)));
+  for (const auto style : injection_styles_) {
+    switch (style) {
+      case PropagationStyle::DATADOG:
+        writer.set("x-datadog-trace-id", std::to_string(span.trace_id));
+        writer.set("x-datadog-parent-id", std::to_string(span.span_id));
+        writer.set("x-datadog-sampling-priority",
+                   std::to_string(sampling_priority));
+        break;
+      case PropagationStyle::B3:
+        writer.set("x-b3-traceid", hex(span.trace_id));
+        writer.set("x-b3-spanid", hex(span.span_id));
+        writer.set("x-b3-sampled", std::to_string(int(sampling_priority > 0)));
+        break;
+      case PropagationStyle::NONE:
+        break;
+    }
   }
 }