From 00be6ee0394809e5ff78cfe6dfedebe10736cf5f Mon Sep 17 00:00:00 2001
From: Willie Abrams <willie@pobox.com>
Date: Tue, 5 Mar 2024 09:42:44 -0600
Subject: [PATCH] support for OTEL_SERVICE_NAME

OTEL_SERVICE_NAME overrides OTEL_RESOURCE_ATTRIBUTES when it is defined.
---
 sdk/src/resource/resource_detector.cc | 36 ++++++++++++++++++---------
 sdk/test/resource/resource_test.cc    | 24 ++++++++++++++++++
 2 files changed, 48 insertions(+), 12 deletions(-)

diff --git a/sdk/src/resource/resource_detector.cc b/sdk/src/resource/resource_detector.cc
index 82e47a71ad..6d74e5d3bb 100644
--- a/sdk/src/resource/resource_detector.cc
+++ b/sdk/src/resource/resource_detector.cc
@@ -15,28 +15,40 @@ namespace resource
 {
 
 const char *OTEL_RESOURCE_ATTRIBUTES = "OTEL_RESOURCE_ATTRIBUTES";
+const char *OTEL_SERVICE_NAME = "OTEL_SERVICE_NAME";
 
 Resource OTELResourceDetector::Detect() noexcept
 {
-  std::string attributes_str;
-  bool exists;
+  std::string attributes_str, service_name;
 
-  exists = opentelemetry::sdk::common::GetStringEnvironmentVariable(OTEL_RESOURCE_ATTRIBUTES,
-                                                                    attributes_str);
-  if (!exists)
+  bool attributes_exists = opentelemetry::sdk::common::GetStringEnvironmentVariable(OTEL_RESOURCE_ATTRIBUTES, attributes_str);
+  bool service_name_exists = opentelemetry::sdk::common::GetStringEnvironmentVariable(OTEL_SERVICE_NAME, service_name);
+
+  if (!attributes_exists && !service_name_exists)
   {
     return Resource();
   }
+
   ResourceAttributes attributes;
-  std::istringstream iss(attributes_str);
-  std::string token;
-  while (std::getline(iss, token, ','))
+
+  if (attributes_exists)
   {
-    size_t pos        = token.find('=');
-    std::string key   = token.substr(0, pos);
-    std::string value = token.substr(pos + 1);
-    attributes[key]   = value;
+    std::istringstream iss(attributes_str);
+    std::string token;
+    while (std::getline(iss, token, ','))
+    {
+      size_t pos        = token.find('=');
+      std::string key   = token.substr(0, pos);
+      std::string value = token.substr(pos + 1);
+      attributes[key]   = value;
+    }
   }
+
+  if (service_name_exists)
+  {
+    attributes["service.name"] = service_name;
+  }
+
   return Resource(attributes);
 }
 
diff --git a/sdk/test/resource/resource_test.cc b/sdk/test/resource/resource_test.cc
index 828a9ac355..e6b56cae43 100644
--- a/sdk/test/resource/resource_test.cc
+++ b/sdk/test/resource/resource_test.cc
@@ -220,6 +220,30 @@ TEST(ResourceTest, OtelResourceDetector)
   unsetenv("OTEL_RESOURCE_ATTRIBUTES");
 }
 
+TEST(ResourceTest, OtelResourceDetectorServiceNameOverride)
+{
+  std::map<std::string, std::string> expected_attributes = {{"service.name", "new_name"}};
+
+  setenv("OTEL_RESOURCE_ATTRIBUTES", "service.name=old_name", 1);
+  setenv("OTEL_SERVICE_NAME", "new_name", 1);
+
+  OTELResourceDetector detector;
+  auto resource            = detector.Detect();
+  auto received_attributes = resource.GetAttributes();
+  for (auto &e : received_attributes)
+  {
+    EXPECT_TRUE(expected_attributes.find(e.first) != expected_attributes.end());
+    if (expected_attributes.find(e.first) != expected_attributes.end())
+    {
+      EXPECT_EQ(expected_attributes.find(e.first)->second, nostd::get<std::string>(e.second));
+    }
+  }
+  EXPECT_EQ(received_attributes.size(), expected_attributes.size());
+
+  unsetenv("OTEL_SERVICE_NAME");
+  unsetenv("OTEL_RESOURCE_ATTRIBUTES");
+}
+
 TEST(ResourceTest, OtelResourceDetectorEmptyEnv)
 {
   std::map<std::string, std::string> expected_attributes = {};