feat!: Set a default service name (DD_SERVICE) when no service is configured (#158)

* feat!: Implement consistency for DD_SERVICE - Set a default service name value when none is provided by DD_SERVICE or configuration

Issues: APMAPI-709

* test: Remove the parametric app's default service and environment configuration so we can test default behaviors

Issues: APMAPI-708 , APMAPI-709

* Apply suggestions from code review

Co-authored-by: Damien Mehala <[email protected]>

* Fix formatting after incorporating code review feedback

---------

Co-authored-by: Damien Mehala <[email protected]>

Author: zacharycmontoya

doc/maintainers.md

@@ -385,7 +385,6 @@ david@ein:~/src/dd-trace-cpp/src/datadog$ sed -n 's/^\s*\(\w\+\)\s*=\s*[0-9]\+,\
       1 SPAN_SAMPLING_RULES_MAX_PER_SECOND_WRONG_TYPE
       1 SPAN_SAMPLING_RULES_INVALID_JSON
       1 SPAN_SAMPLING_RULES_FILE_IO
-      1 SERVICE_NAME_REQUIRED
       1 RULE_WRONG_TYPE
       1 RULE_TAG_WRONG_TYPE
       1 RULE_PROPERTY_WRONG_TYPE

include/datadog/error.h

@@ -24,7 +24,7 @@ struct Error {
   // versions.
   enum Code {
     OTHER = 1,
-    SERVICE_NAME_REQUIRED = 2,
+    // SERVICE_NAME_REQUIRED = 2,
     MESSAGEPACK_ENCODE_FAILURE = 3,
     CURL_REQUEST_FAILURE = 4,
     DATADOG_AGENT_NULL_HTTP_CLIENT = 5,

src/datadog/platform_util.cpp

@@ -189,6 +189,29 @@ int get_process_id() {
 #endif
 }
 
+std::string get_process_name() {
+#if defined(__APPLE__) || defined(__FreeBSD__)
+  char* process_name = getprogname();
+  return (process_name != nullptr) ? process_name : "unknown-service";
+#elif defined(__linux__) || defined(__unix__)
+  return program_invocation_short_name;
+#elif defined(_MSC_VER)
+  TCHAR exe_name[MAX_PATH];
+  if (GetModuleFileName(NULL, exe_name, MAX_PATH) <= 0) {
+    return "unknown-service";
+  }
+#ifdef UNICODE
+  std::wstring wStr(exe_name);
+  std::string path = std::string(wStr.begin(), wStr.end());
+#else
+  std::string path = std::string(exe_name);
+#endif
+  return path.substr(path.find_last_of("/\\") + 1);
+#else
+  return "unknown-service";
+#endif
+}
+
 int at_fork_in_child(void (*on_fork)()) {
 #if defined(_MSC_VER)
   // Windows does not have `fork`, and so this is not relevant there.

src/datadog/platform_util.h

@@ -26,6 +26,8 @@ std::string get_hostname();
 
 int get_process_id();
 
+std::string get_process_name();
+
 int at_fork_in_child(void (*on_fork)());
 
 }  // namespace tracing

src/datadog/tracer_config.cpp

@@ -15,6 +15,7 @@
 #include "datadog_agent.h"
 #include "json.hpp"
 #include "parse_util.h"
+#include "platform_util.h"
 #include "string_util.h"
 
 namespace datadog {
@@ -263,7 +264,7 @@ Expected<FinalizedTracerConfig> finalize_config(const TracerConfig &user_config,
       pick(env_config->service, user_config.service, "");
 
   if (final_config.defaults.service.empty()) {
-    return Error{Error::SERVICE_NAME_REQUIRED, "Service name is required."};
+    final_config.defaults.service = get_process_name();
   }
 
   final_config.metadata[ConfigName::SERVICE_NAME] = ConfigMetadata(

test/system-tests/main.cpp

@@ -77,8 +77,6 @@ int main(int argc, char* argv[]) {
   datadog::tracing::TracerConfig config;
   config.logger = logger;
   config.agent.event_scheduler = event_scheduler;
-  config.service = "cpp-parametric-test";
-  config.environment = "staging";
   config.name = "http.request";
 
   auto finalized_config = datadog::tracing::finalize_config(config);

test/test_tracer_config.cpp

@@ -145,16 +145,21 @@ class SomewhatSecureTemporaryFile : public std::fstream {
 TEST_CASE("TracerConfig::defaults") {
   TracerConfig config;
 
-  SECTION("service is required") {
+  SECTION("service is not required") {
     SECTION("empty") {
       auto finalized = finalize_config(config);
-      REQUIRE(!finalized);
-      REQUIRE(finalized.error().code == Error::SERVICE_NAME_REQUIRED);
+      REQUIRE(finalized);
+#ifdef _MSC_VER
+      REQUIRE(finalized->defaults.service == "tests.exe");
+#else
+      REQUIRE(finalized->defaults.service == "tests");
+#endif
     }
     SECTION("nonempty") {
       config.service = "testsvc";
       auto finalized = finalize_config(config);
       REQUIRE(finalized);
+      REQUIRE(finalized->defaults.service == "testsvc");
     }
   }