collect all config sources in tracer_config in a map

Author: anna-git

include/datadog/config.h

@@ -1,5 +1,11 @@
 #pragma once
 
+#include <string>
+#include <type_traits>
+#include <unordered_map>
+#include <utility>
+#include <vector>
+
 #include "error.h"
 #include "optional.h"
 
@@ -56,14 +62,72 @@ struct ConfigMetadata {
       : name(n), value(std::move(v)), origin(orig), error(std::move(err)) {}
 };
 
+// Return the chosen configuration value, in order of precedence: `from_env`,
+// `from_user`, and `fallback`.
+// This overload directly populates both telemetry_configs[config_name] and
+// metadata[config_name] using the stringified value, with all values found,
+// from lowest to highest precedence. Returns the chosen value directly.
+//
+// The fallback parameter is optional and defaults to nullptr.
+template <typename Value, typename Stringifier = std::nullptr_t,
+          typename DefaultValue = std::nullptr_t>
+Value pick(const Optional<Value>& from_env, const Optional<Value>& from_user,
+           std::unordered_map<ConfigName, std::vector<ConfigMetadata>>*
+               telemetry_configs,
+           std::unordered_map<ConfigName, ConfigMetadata>* metadata,
+           ConfigName config_name, DefaultValue fallback = nullptr,
+           Stringifier to_string_fn = nullptr) {
+  auto stringify = [&](const Value& v) -> std::string {
+    if constexpr (!std::is_same_v<Stringifier, std::nullptr_t>) {
+      return to_string_fn(v);  // use provided function
+    } else if constexpr (std::is_constructible_v<std::string, Value>) {
+      return std::string(v);  // default behaviour (works for string-like types)
+    } else {
+      static_assert(!std::is_same_v<Value, Value>,
+                    "Non-string types require a stringifier function");
+      return "";  // unreachable
+    }
+  };
+
+  std::vector<ConfigMetadata> telemetry_entries;
+  Optional<Value> chosen_value;
+
+  auto add_entry = [&](ConfigMetadata::Origin origin, const Value& val) {
+    std::string val_str = stringify(val);
+    telemetry_entries.emplace_back(
+        ConfigMetadata{config_name, val_str, origin});
+    chosen_value = val;
+  };
+
+  // Add DEFAULT entry if fallback was provided (detected by type)
+  if constexpr (!std::is_same_v<DefaultValue, std::nullptr_t>) {
+    add_entry(ConfigMetadata::Origin::DEFAULT, fallback);
+  }
+
+  if (from_user) {
+    add_entry(ConfigMetadata::Origin::CODE, *from_user);
+  }
+
+  if (from_env) {
+    add_entry(ConfigMetadata::Origin::ENVIRONMENT_VARIABLE, *from_env);
+  }
+
+  (*telemetry_configs)[config_name] = std::move(telemetry_entries);
+  if (!(*telemetry_configs)[config_name].empty()) {
+    (*metadata)[config_name] = (*telemetry_configs)[config_name].back();
+  }
+
+  return chosen_value.value_or(Value{});
+}
+
 // Return a pair containing the configuration origin and value of a
 // configuration value chosen from one of the specified `from_env`,
 // `from_config`, and `fallback`. This function defines the relative precedence
 // among configuration values originating from the environment, programmatic
 // configuration, and default configuration.
 template <typename Value, typename DefaultValue>
-std::pair<ConfigMetadata::Origin, Value> pick(const Optional<Value> &from_env,
-                                              const Optional<Value> &from_user,
+std::pair<ConfigMetadata::Origin, Value> pick(const Optional<Value>& from_env,
+                                              const Optional<Value>& from_user,
                                               DefaultValue fallback) {
   if (from_env) {
     return {ConfigMetadata::Origin::ENVIRONMENT_VARIABLE, *from_env};

include/datadog/telemetry/product.h

@@ -5,6 +5,7 @@
 
 #include <string>
 #include <unordered_map>
+#include <vector>
 
 namespace datadog::telemetry {
 
@@ -30,7 +31,7 @@ struct Product final {
   /// Optional error message related to the product status.
   tracing::Optional<std::string> error_message;
   /// Map of configuration settings for the product.
-  std::unordered_map<tracing::ConfigName, tracing::ConfigMetadata>
+  std::unordered_map<tracing::ConfigName, std::vector<tracing::ConfigMetadata>>
       configurations;
 };
 

src/datadog/tracer_config.cpp

@@ -8,13 +8,13 @@
 #include <unordered_map>
 #include <vector>
 
+#include "datadog/optional.h"
 #include "datadog_agent.h"
 #include "json.hpp"
 #include "null_logger.h"
 #include "parse_util.h"
 #include "platform_util.h"
 #include "string_util.h"
-#include "tags.h"
 #include "threaded_event_scheduler.h"
 
 namespace datadog {
@@ -284,81 +284,81 @@ Expected<FinalizedTracerConfig> finalize_config(const TracerConfig &user_config,
   final_config.clock = clock;
   final_config.logger = logger;
 
-  ConfigMetadata::Origin origin;
+  std::unordered_map<ConfigName, std::vector<ConfigMetadata>>
+      all_sources_configs;
 
-  std::tie(origin, final_config.defaults.service) =
-      pick(env_config->service, user_config.service, "");
-
-  if (final_config.defaults.service.empty()) {
-    final_config.defaults.service = get_process_name();
-  }
-
-  final_config.metadata[ConfigName::SERVICE_NAME] = ConfigMetadata(
-      ConfigName::SERVICE_NAME, final_config.defaults.service, origin);
+  // DD_SERVICE
+  final_config.defaults.service = pick(
+      env_config->service, user_config.service, &all_sources_configs,
+      &final_config.metadata, ConfigName::SERVICE_NAME, get_process_name());
 
+  // Service type
   final_config.defaults.service_type =
       value_or(env_config->service_type, user_config.service_type, "web");
 
   // DD_ENV
-  std::tie(origin, final_config.defaults.environment) =
-      pick(env_config->environment, user_config.environment, "");
-  final_config.metadata[ConfigName::SERVICE_ENV] = ConfigMetadata(
-      ConfigName::SERVICE_ENV, final_config.defaults.environment, origin);
+  final_config.defaults.environment = pick(
+      env_config->environment, user_config.environment, &all_sources_configs,
+      &final_config.metadata, ConfigName::SERVICE_ENV);
 
   // DD_VERSION
-  std::tie(origin, final_config.defaults.version) =
-      pick(env_config->version, user_config.version, "");
-  final_config.metadata[ConfigName::SERVICE_VERSION] = ConfigMetadata(
-      ConfigName::SERVICE_VERSION, final_config.defaults.version, origin);
+  final_config.defaults.version =
+      pick(env_config->version, user_config.version, &all_sources_configs,
+           &final_config.metadata, ConfigName::SERVICE_VERSION);
 
+  // Span name
   final_config.defaults.name = value_or(env_config->name, user_config.name, "");
 
   // DD_TAGS
-  std::tie(origin, final_config.defaults.tags) =
-      pick(env_config->tags, user_config.tags,
-           std::unordered_map<std::string, std::string>{});
-  final_config.metadata[ConfigName::TAGS] = ConfigMetadata(
-      ConfigName::TAGS, join_tags(final_config.defaults.tags), origin);
+  final_config.defaults.tags =
+      pick(env_config->tags, user_config.tags, &all_sources_configs,
+           &final_config.metadata, ConfigName::TAGS,
+           std::unordered_map<std::string, std::string>{},
+           [](const auto &tags) { return join_tags(tags); });
 
   // Extraction Styles
   const std::vector<PropagationStyle> default_propagation_styles{
       PropagationStyle::DATADOG, PropagationStyle::W3C,
       PropagationStyle::BAGGAGE};
 
-  std::tie(origin, final_config.extraction_styles) =
+  final_config.extraction_styles =
       pick(env_config->extraction_styles, user_config.extraction_styles,
-           default_propagation_styles);
+           &all_sources_configs, &final_config.metadata,
+           ConfigName::EXTRACTION_STYLES, default_propagation_styles,
+           [](const std::vector<PropagationStyle> &styles) {
+             return join_propagation_styles(styles);
+           });
+
   if (final_config.extraction_styles.empty()) {
     return Error{Error::MISSING_SPAN_EXTRACTION_STYLE,
                  "At least one extraction style must be specified."};
   }
-  final_config.metadata[ConfigName::EXTRACTION_STYLES] = ConfigMetadata(
-      ConfigName::EXTRACTION_STYLES,
-      join_propagation_styles(final_config.extraction_styles), origin);
 
   // Injection Styles
-  std::tie(origin, final_config.injection_styles) =
+  final_config.injection_styles =
       pick(env_config->injection_styles, user_config.injection_styles,
-           default_propagation_styles);
+           &all_sources_configs, &final_config.metadata,
+           ConfigName::INJECTION_STYLES, default_propagation_styles,
+           [](const std::vector<PropagationStyle> &styles) {
+             return join_propagation_styles(styles);
+           });
+
   if (final_config.injection_styles.empty()) {
     return Error{Error::MISSING_SPAN_INJECTION_STYLE,
                  "At least one injection style must be specified."};
   }
-  final_config.metadata[ConfigName::INJECTION_STYLES] = ConfigMetadata(
-      ConfigName::INJECTION_STYLES,
-      join_propagation_styles(final_config.injection_styles), origin);
 
   // Startup Logs
-  std::tie(origin, final_config.log_on_startup) =
-      pick(env_config->log_on_startup, user_config.log_on_startup, true);
-  final_config.metadata[ConfigName::STARTUP_LOGS] = ConfigMetadata(
-      ConfigName::STARTUP_LOGS, to_string(final_config.log_on_startup), origin);
+  final_config.log_on_startup = pick(
+      env_config->log_on_startup, user_config.log_on_startup,
+      &all_sources_configs, &final_config.metadata, ConfigName::STARTUP_LOGS,
+      true, [](const bool &b) { return to_string(b); });
 
   // Report traces
-  std::tie(origin, final_config.report_traces) =
-      pick(env_config->report_traces, user_config.report_traces, true);
-  final_config.metadata[ConfigName::REPORT_TRACES] = ConfigMetadata(
-      ConfigName::REPORT_TRACES, to_string(final_config.report_traces), origin);
+  final_config.report_traces = pick(
+      env_config->report_traces, user_config.report_traces,
+      &all_sources_configs, &final_config.metadata, ConfigName::REPORT_TRACES,
+      true, [](const bool &b) { return to_string(b); });
 
   // Report hostname
   final_config.report_hostname =
@@ -369,12 +369,11 @@ Expected<FinalizedTracerConfig> finalize_config(const TracerConfig &user_config,
       env_config->max_tags_header_size, user_config.max_tags_header_size, 512);
 
   // 128b Trace IDs
-  std::tie(origin, final_config.generate_128bit_trace_ids) =
+  final_config.generate_128bit_trace_ids =
       pick(env_config->generate_128bit_trace_ids,
-           user_config.generate_128bit_trace_ids, true);
-  final_config.metadata[ConfigName::GENEREATE_128BIT_TRACE_IDS] =
-      ConfigMetadata(ConfigName::GENEREATE_128BIT_TRACE_IDS,
-                     to_string(final_config.generate_128bit_trace_ids), origin);
+           user_config.generate_128bit_trace_ids, &all_sources_configs,
+           &final_config.metadata, ConfigName::GENEREATE_128BIT_TRACE_IDS, true,
+           [](const bool &b) { return to_string(b); });
 
   // Integration name & version
   final_config.integration_name = value_or(
@@ -383,18 +382,19 @@ Expected<FinalizedTracerConfig> finalize_config(const TracerConfig &user_config,
       value_or(env_config->integration_version, user_config.integration_version,
                tracer_version);
 
-  // Baggage
-  std::tie(origin, final_config.baggage_opts.max_items) =
-      pick(env_config->baggage_max_items, user_config.baggage_max_items, 64);
-  final_config.metadata[ConfigName::TRACE_BAGGAGE_MAX_ITEMS] = ConfigMetadata(
-      ConfigName::TRACE_BAGGAGE_MAX_ITEMS,
-      std::to_string(final_config.baggage_opts.max_items), origin);
-
-  std::tie(origin, final_config.baggage_opts.max_bytes) =
-      pick(env_config->baggage_max_bytes, user_config.baggage_max_bytes, 8192);
-  final_config.metadata[ConfigName::TRACE_BAGGAGE_MAX_BYTES] = ConfigMetadata(
-      ConfigName::TRACE_BAGGAGE_MAX_BYTES,
-      std::to_string(final_config.baggage_opts.max_bytes), origin);
+  // Baggage - max items
+  final_config.baggage_opts.max_items =
+      pick(env_config->baggage_max_items, user_config.baggage_max_items,
+           &all_sources_configs, &final_config.metadata,
+           ConfigName::TRACE_BAGGAGE_MAX_ITEMS, 64UL,
+           [](const size_t &i) { return std::to_string(i); });
+
+  // Baggage - max bytes
+  final_config.baggage_opts.max_bytes =
+      pick(env_config->baggage_max_bytes, user_config.baggage_max_bytes,
+           &all_sources_configs, &final_config.metadata,
+           ConfigName::TRACE_BAGGAGE_MAX_BYTES, 8192UL,
+           [](const size_t &i) { return std::to_string(i); });
 
   if (final_config.baggage_opts.max_items <= 0 ||
       final_config.baggage_opts.max_bytes < 3) {
@@ -453,39 +453,33 @@ Expected<FinalizedTracerConfig> finalize_config(const TracerConfig &user_config,
     final_config.telemetry = std::move(*telemetry_final_config);
     final_config.telemetry.products.emplace_back(telemetry::Product{
         telemetry::Product::Name::tracing, true, tracer_version, nullopt,
-        nullopt, final_config.metadata});
+        nullopt, all_sources_configs});
   } else {
     return std::move(telemetry_final_config.error());
   }
 
   // APM Tracing Enabled
-  std::tie(origin, final_config.tracing_enabled) =
-      pick(env_config->tracing_enabled, user_config.tracing_enabled, true);
-  final_config.metadata[ConfigName::APM_TRACING_ENABLED] =
-      ConfigMetadata(ConfigName::APM_TRACING_ENABLED,
-                     to_string(final_config.tracing_enabled), origin);
+  final_config.tracing_enabled =
+      pick(env_config->tracing_enabled, user_config.tracing_enabled,
+           &all_sources_configs, &final_config.metadata,
+           ConfigName::APM_TRACING_ENABLED, true,
+           [](const bool &b) { return to_string(b); });
 
   {
     // Resource Renaming Enabled
-    bool resource_renaming_enabled;
-    std::tie(origin, resource_renaming_enabled) =
-        pick(env_config->resource_renaming_enabled,
-             user_config.resource_renaming_enabled, false);
-
-    final_config.metadata[ConfigName::TRACE_RESOURCE_RENAMING_ENABLED] =
-        ConfigMetadata(ConfigName::TRACE_RESOURCE_RENAMING_ENABLED,
-                       to_string(resource_renaming_enabled), origin);
+    const bool resource_renaming_enabled = pick(
+        env_config->resource_renaming_enabled,
+        user_config.resource_renaming_enabled, &all_sources_configs,
+        &final_config.metadata, ConfigName::TRACE_RESOURCE_RENAMING_ENABLED,
+        false, [](const bool &b) { return to_string(b); });
 
     // Resource Renaming Always Simplified Endpoint
-    bool resource_renaming_always_simplified_endpoint;
-    std::tie(origin, resource_renaming_always_simplified_endpoint) =
+    const bool resource_renaming_always_simplified_endpoint =
         pick(env_config->resource_renaming_always_simplified_endpoint,
-             user_config.resource_renaming_always_simplified_endpoint, false);
-    final_config.metadata
-        [ConfigName::TRACE_RESOURCE_RENAMING_ALWAYS_SIMPLIFIED_ENDPOINT] =
-        ConfigMetadata(
-            ConfigName::TRACE_RESOURCE_RENAMING_ALWAYS_SIMPLIFIED_ENDPOINT,
-            to_string(resource_renaming_always_simplified_endpoint), origin);
+             user_config.resource_renaming_always_simplified_endpoint,
+             &all_sources_configs, &final_config.metadata,
+             ConfigName::TRACE_RESOURCE_RENAMING_ALWAYS_SIMPLIFIED_ENDPOINT,
+             false, [](const bool &b) { return to_string(b); });
 
     if (!resource_renaming_enabled) {
       final_config.resource_renaming_mode =