feat: support disablement of APM Tracing (the product) (#224)

Co-authored-by: Gustavo Lopes <[email protected]>

Author: dmehala

BUILD.bazel

@@ -42,6 +42,7 @@ cc_library(
       "src/datadog/string_util.cpp",
       "src/datadog/tag_propagation.cpp",
       "src/datadog/tags.cpp",
+      "src/datadog/trace_source.cpp",
       "src/datadog/telemetry_metrics.cpp",
       "src/datadog/threaded_event_scheduler.cpp",
       "src/datadog/tracer_config.cpp",
@@ -117,6 +118,7 @@ cc_library(
       "include/datadog/tracer_config.h",
       "include/datadog/tracer_signature.h",
       "include/datadog/trace_id.h",
+      "include/datadog/trace_source.h",
       "include/datadog/trace_sampler_config.h",
       "include/datadog/trace_segment.h",
       "include/datadog/version.h",

CMakeLists.txt

@@ -150,6 +150,7 @@ target_sources(dd_trace_cpp-objects
     src/datadog/trace_sampler_config.cpp
     src/datadog/trace_sampler.cpp
     src/datadog/trace_segment.cpp
+    src/datadog/trace_source.cpp
     src/datadog/telemetry_metrics.cpp
     src/datadog/version.cpp
     src/datadog/w3c_propagation.cpp

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

@@ -22,7 +22,6 @@
 #include "expected.h"
 #include "http_client.h"
 #include "remote_config/listener.h"
-#include "string_view.h"
 
 namespace datadog {
 namespace tracing {
@@ -90,6 +89,11 @@ class FinalizedDatadogAgentConfig {
 
   // Origin detection
   Optional<std::string> admission_controller_uid;
+
+  // Indicate if stats computation should be delegated to the Agent.
+  // This feature is not supported yet, however, we need to inform the Agent to
+  // not compute stats when APM Tracing `DD_APM_TRACING_ENABLED` is disabled.
+  bool stats_computation_enabled;
 };
 
 Expected<FinalizedDatadogAgentConfig> finalize_config(

include/datadog/dict_writer.h

@@ -21,6 +21,9 @@ class DictWriter {
   // implementation may, but is not required to, overwrite any previous value at
   // `key`.
   virtual void set(StringView key, StringView value) = 0;
+
+  // Removes the entry associated with the given key.
+  virtual void erase(StringView){};
 };
 
 }  // namespace tracing

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/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/span.h

@@ -49,6 +49,7 @@
 #include "optional.h"
 #include "string_view.h"
 #include "trace_id.h"
+#include "trace_source.h"
 
 namespace datadog {
 namespace tracing {
@@ -162,6 +163,8 @@ class Span {
   // Set end time of this span.  Doing so will override the default behavior of
   // using the current time in the destructor.
   void set_end_time(std::chrono::steady_clock::time_point);
+  // Specifies the product (AppSec, DBM) that created this span.
+  void set_source(Source);
 
   // Write information about this span and its trace into the specified `writer`
   // using all of the configured injection propagation styles.

include/datadog/trace_sampler_config.h

@@ -24,6 +24,7 @@ struct TraceSamplerRule final {
   Rate rate;
   SpanMatcher matcher;
   SamplingMechanism mechanism;
+  bool bypass_limiter = false;
 };
 
 struct TraceSamplerConfig {
@@ -50,6 +51,10 @@ class FinalizedTraceSamplerConfig {
   double max_per_second;
   std::vector<TraceSamplerRule> rules;
   std::unordered_map<ConfigName, ConfigMetadata> metadata;
+
+ public:
+  /// Returns the trace sampler configuration when APM Tracing is disabled.
+  static FinalizedTraceSamplerConfig apm_tracing_disabled_config();
 };
 
 Expected<FinalizedTraceSamplerConfig> finalize_config(

include/datadog/trace_segment.h

@@ -32,7 +32,6 @@
 #include <utility>
 #include <vector>
 
-#include "expected.h"
 #include "optional.h"
 #include "propagation_style.h"
 #include "runtime_id.h"
@@ -80,6 +79,8 @@ class TraceSegment {
 
   std::shared_ptr<ConfigManager> config_manager_;
 
+  bool tracing_enabled_;
+
  public:
   TraceSegment(const std::shared_ptr<Logger>& logger,
                const std::shared_ptr<Collector>& collector,
@@ -95,7 +96,8 @@ class TraceSegment {
                Optional<SamplingDecision> sampling_decision,
                Optional<std::string> additional_w3c_tracestate,
                Optional<std::string> additional_datadog_w3c_tracestate,
-               std::unique_ptr<SpanData> local_root);
+               std::unique_ptr<SpanData> local_root,
+               bool tracing_enabled = true);
 
   const SpanDefaults& defaults() const;
   const Optional<std::string>& hostname() const;
@@ -118,10 +120,13 @@ class TraceSegment {
   void span_finished();
 
   // Set the sampling decision to be a local, manual decision with the specified
-  // sampling `priority`.  Overwrite any previous sampling decision.
+  // sampling `priority`. Overwrite any previous sampling decision.
   void override_sampling_priority(int priority);
   void override_sampling_priority(SamplingPriority priority);
 
+  // Retrieves the local root span.
+  SpanData& local_root() const;
+
  private:
   // If `sampling_decision_` is null, use `trace_sampler_` to make a
   // sampling decision and assign it to `sampling_decision_`.