always use latest exit span to inject propagation header (#89)

Author: Shikugawa

cpp2sky/tracing_context.h

@@ -234,14 +234,9 @@ class TracingContext {
 
   /**
    * Generate sw8 value to send SegmentRef.
-   * @param parent Parent span that belongs to current segment.
    * @param target_address Target address to send request. For more detail:
    * https://github.com/apache/skywalking-data-collect-protocol/blob/master/language-agent/Tracing.proto#L97-L101
    */
-  virtual std::optional<std::string> createSW8HeaderValue(
-      TracingSpanPtr parent, const std::string_view target_address) = 0;
-  // If you don't specify parent span, stored to current segment, it will be
-  // selected newest span as parent span.
   virtual std::optional<std::string> createSW8HeaderValue(
       const std::string_view target_address) = 0;
 

example/sample_client.cc

@@ -56,7 +56,7 @@ int main() {
    * httplib::Client cli("remote", 8082);
    * httplib::Headers headers = {
    *   {kPropagationHeader.data(),
-   *   tracing_context->createSW8HeaderValue(current_span, "remote:8082")}};
+   *   tracing_context->createSW8HeaderValue("remote:8082")}};
    *
    * auto res = cli.Get("/ping", headers);
    *
@@ -74,8 +74,8 @@ int main() {
 
       httplib::Client cli("127.0.0.1", 8081);
       httplib::Headers headers = {
-          {kPropagationHeader.data(), *tracing_context->createSW8HeaderValue(
-                                          exit_span.get(), target_address)}};
+          {kPropagationHeader.data(),
+           *tracing_context->createSW8HeaderValue(target_address)}};
 
       auto res = cli.Get("/ping", headers);
     }

source/tracing_context_impl.cc

@@ -192,16 +192,8 @@ TracingSpanPtr TracingContextImpl::createEntrySpan() {
 }
 
 std::optional<std::string> TracingContextImpl::createSW8HeaderValue(
-    TracingSpanPtr parent_span, const std::string_view target_address) {
-  TracingSpanPtr target_span = parent_span;
-  if (target_span == nullptr) {
-    if (spans_.empty()) {
-      throw TracerException(
-          "Can't create propagation header because current segment has no "
-          "valid span.");
-    }
-    target_span = spans_.back();
-  }
+    const std::string_view target_address) {
+  auto target_span = spans_.back();
   if (target_span->spanType() != skywalking::v3::SpanType::Exit) {
     return std::nullopt;
   }

source/tracing_context_impl.h

@@ -145,11 +145,6 @@ class TracingContextImpl : public TracingContext {
 
   TracingSpanPtr createEntrySpan() override;
   std::optional<std::string> createSW8HeaderValue(
-      const std::string_view target_address) override {
-    return createSW8HeaderValue(nullptr, target_address);
-  }
-  std::optional<std::string> createSW8HeaderValue(
-      TracingSpanPtr parent_span,
       const std::string_view target_address) override;
   skywalking::v3::SegmentObject createSegmentObject() override;
   void setSkipAnalysis() override { should_skip_analysis_ = true; }

test/e2e/provider.cc

@@ -51,8 +51,8 @@ int main() {
 
         httplib::Client cli("consumer", 8080);
         httplib::Headers headers = {
-            {kPropagationHeader.data(), *tracing_context->createSW8HeaderValue(
-                                            exit_span.get(), target_address)}};
+            {kPropagationHeader.data(),
+             *tracing_context->createSW8HeaderValue(target_address)}};
         auto res = cli.Get("/pong", headers);
       }
     }
@@ -75,8 +75,8 @@ int main() {
 
         httplib::Client cli("interm", 8082);
         httplib::Headers headers = {
-            {kPropagationHeader.data(), *tracing_context->createSW8HeaderValue(
-                                            exit_span.get(), target_address)}};
+            {kPropagationHeader.data(),
+             *tracing_context->createSW8HeaderValue(target_address)}};
         auto res = cli.Get("/users", headers);
       }
     }

test/tracing_context_test.cc

@@ -329,7 +329,7 @@ TEST_F(TracingContextTest, SW8CreateTest) {
   std::string target_address("10.0.0.1:443");
 
   // Entry span should be rejected as propagation context
-  EXPECT_FALSE(sc.createSW8HeaderValue(span, target_address).has_value());
+  EXPECT_FALSE(sc.createSW8HeaderValue(target_address).has_value());
 
   auto span2 = sc.createExitSpan(span);
 
@@ -341,7 +341,7 @@ TEST_F(TracingContextTest, SW8CreateTest) {
   std::string expect_sw8(
       "1-MQ==-dXVpZA==-1-bWVzaA==-c2VydmljZV8w-c2FtcGxlMQ==-MTAuMC4wLjE6NDQz");
 
-  EXPECT_EQ(expect_sw8, *sc.createSW8HeaderValue(span2, target_address));
+  EXPECT_EQ(expect_sw8, *sc.createSW8HeaderValue(target_address));
 
   std::vector<char> target_address_based_vector;
   target_address_based_vector.reserve(target_address.size() * 2);
@@ -354,14 +354,14 @@ TEST_F(TracingContextTest, SW8CreateTest) {
 
   EXPECT_EQ(target_address_based_vector.size(), target_address.size());
   EXPECT_EQ(expect_sw8,
-            *sc.createSW8HeaderValue(span2, target_address_based_vector_view));
+            *sc.createSW8HeaderValue(target_address_based_vector_view));
 
   // Make sure that the end of target_address_based_vector_view is not '\0'. We
   // reserve enough memory for target_address_based_vector, so push back will
   // not cause content to be re-allocated.
   target_address_based_vector.push_back('x');
   EXPECT_EQ(expect_sw8,
-            *sc.createSW8HeaderValue(span2, target_address_based_vector_view));
+            *sc.createSW8HeaderValue(target_address_based_vector_view));
 }
 
 TEST_F(TracingContextTest, ReadyToSendTest) {