Implement DD_TRACE_ENABLED=false

Author: cataphract

include/datadog/collector.h

@@ -19,7 +19,7 @@ namespace datadog {
 namespace tracing {
 
 struct SpanData;
-class TraceSampler;
+class ErasedTraceSampler;
 
 class Collector {
  public:
@@ -29,7 +29,7 @@ class Collector {
   // occurs.
   virtual Expected<void> send(
       std::vector<std::unique_ptr<SpanData>>&& spans,
-      const std::shared_ptr<TraceSampler>& response_handler) = 0;
+      const std::shared_ptr<ErasedTraceSampler>& response_handler) = 0;
 
   // Return a JSON representation of this object's configuration. The JSON
   // representation is an object with the following properties:

include/datadog/config.h

@@ -27,6 +27,7 @@ enum class ConfigName : char {
   SPAN_SAMPLING_RULES,
   TRACE_BAGGAGE_MAX_BYTES,
   TRACE_BAGGAGE_MAX_ITEMS,
+  APM_TRACING_ENABLED,
 };
 
 // Represents metadata for configuration parameters

include/datadog/datadog_agent_config.h

@@ -66,6 +66,9 @@ struct DatadogAgentConfig {
   // How often, in seconds, to query the Datadog Agent for remote configuration
   // updates.
   Optional<double> remote_configuration_poll_interval_seconds;
+  // Whether APM tracing is enabled. This affects whether the
+  // "Datadog-Client-Computed-Stats: yes" header is sent with trace requests.
+  Optional<bool> apm_tracing_enabled;
 };
 
 class FinalizedDatadogAgentConfig {
@@ -87,6 +90,7 @@ class FinalizedDatadogAgentConfig {
   std::chrono::steady_clock::duration shutdown_timeout;
   std::chrono::steady_clock::duration remote_configuration_poll_interval;
   std::unordered_map<ConfigName, ConfigMetadata> metadata;
+  bool apm_tracing_enabled;
 
   // Origin detection
   Optional<std::string> admission_controller_uid;

include/datadog/environment.h

@@ -60,6 +60,7 @@ namespace environment {
   MACRO(DD_INSTRUMENTATION_INSTALL_ID)               \
   MACRO(DD_INSTRUMENTATION_INSTALL_TYPE)             \
   MACRO(DD_INSTRUMENTATION_INSTALL_TIME)             \
+  MACRO(DD_APM_TRACING_ENABLED)                      \
   MACRO(DD_EXTERNAL_ENV)
 
 #define WITH_COMMA(ARG) ARG,

include/datadog/injection_options.h

@@ -7,7 +7,9 @@
 namespace datadog {
 namespace tracing {
 
-struct InjectionOptions {};
+struct InjectionOptions {
+  bool has_appsec_matches{};
+};
 
 }  // namespace tracing
 }  // namespace datadog

include/datadog/null_collector.h

@@ -11,7 +11,7 @@ namespace tracing {
 class NullCollector : public Collector {
  public:
   Expected<void> send(std::vector<std::unique_ptr<SpanData>>&&,
-                      const std::shared_ptr<TraceSampler>&) override {
+                      const std::shared_ptr<ErasedTraceSampler>&) override {
     return {};
   }
 

include/datadog/sampling_mechanism.h

@@ -49,7 +49,7 @@ enum class SamplingMechanism {
   // The sampling decision was made explicitly by the user, who set a sampling
   // priority.
   MANUAL = 4,
-  // Reserved for future use.
+  // Trace was kept because of AppSec event.
   APP_SEC = 5,
   // Reserved for future use.
   REMOTE_RATE_USER_DEFINED = 6,

include/datadog/trace_segment.h

@@ -53,15 +53,16 @@ class Logger;
 struct SpanData;
 struct SpanDefaults;
 class SpanSampler;
-class TraceSampler;
+class ErasedTraceSampler;
 class ConfigManager;
 
 class TraceSegment {
   mutable std::mutex mutex_;
 
   std::shared_ptr<Logger> logger_;
   std::shared_ptr<Collector> collector_;
-  std::shared_ptr<TraceSampler> trace_sampler_;
+  std::shared_ptr<ErasedTraceSampler> trace_sampler_;
+  bool apm_tracing_enabled_;
   std::shared_ptr<SpanSampler> span_sampler_;
 
   std::shared_ptr<const SpanDefaults> defaults_;
@@ -83,7 +84,8 @@ class TraceSegment {
  public:
   TraceSegment(const std::shared_ptr<Logger>& logger,
                const std::shared_ptr<Collector>& collector,
-               const std::shared_ptr<TraceSampler>& trace_sampler,
+               std::shared_ptr<ErasedTraceSampler> trace_sampler,
+               bool apm_tracing_enabled,
                const std::shared_ptr<SpanSampler>& span_sampler,
                const std::shared_ptr<const SpanDefaults>& defaults,
                const std::shared_ptr<ConfigManager>& config_manager,

include/datadog/tracer.h

@@ -29,7 +29,7 @@ namespace tracing {
 class ConfigManager;
 class DictReader;
 struct SpanConfig;
-class TraceSampler;
+class ErasedTraceSampler;
 class SpanSampler;
 class IDGenerator;
 class InMemoryFile;
@@ -39,6 +39,8 @@ class Tracer {
   RuntimeID runtime_id_;
   TracerSignature signature_;
   std::shared_ptr<ConfigManager> config_manager_;
+  std::shared_ptr<ErasedTraceSampler>
+      apm_tracing_disabled_sampler_;  // empty if enabled
   std::shared_ptr<Collector> collector_;
   std::shared_ptr<SpanSampler> span_sampler_;
   std::shared_ptr<const IDGenerator> generator_;
@@ -104,6 +106,10 @@ class Tracer {
   // same JSON object that was logged when this Tracer was created.
   std::string config() const;
 
+  bool is_apm_tracing_enabled() const {
+    return apm_tracing_disabled_sampler_ == nullptr;
+  }
+
  private:
   void store_config();
 };

include/datadog/tracer_config.h

@@ -28,6 +28,7 @@ class Collector;
 class Logger;
 class SpanSampler;
 class TraceSampler;
+class ErasedTraceSampler;
 
 struct TracerConfig {
   // Set the service name.
@@ -80,6 +81,16 @@ struct TracerConfig {
   // `telemetry/configuration.h` By default, the telemetry module is enabled.
   telemetry::Configuration telemetry;
 
+  // `apm_tracing_enabled` indicates whether APM traces and APM trace metrics
+  // are enabled. If `false`, APM-specific traces are dropped and APM trace
+  // metrics are not computed. This allows other products (e.g., AppSec) to
+  // operate independently.
+  // This is distinct from `report_traces`, which controls whether any traces
+  // are sent at all.
+  // `apm_tracing_enabled` is overridden by the `DD_APM_TRACING_ENABLED`
+  // environment variable. Defaults to `true`.
+  Optional<bool> apm_tracing_enabled;
+
   // `trace_sampler` configures trace sampling.  Trace sampling determines which
   // traces are sent to Datadog.  See `trace_sampler_config.h`.
   TraceSamplerConfig trace_sampler;
@@ -197,6 +208,7 @@ class FinalizedTracerConfig final {
   std::shared_ptr<Logger> logger;
   bool log_on_startup;
   bool generate_128bit_trace_ids;
+  bool apm_tracing_enabled;
   Optional<RuntimeID> runtime_id;
   Clock clock;
   std::string integration_name;