doc 'till you drop

Author: dgoffredo

src/datadog/runtime_id.h

@@ -1,6 +1,10 @@
 #pragma once
 
-// TODO: document
+// This component provides a `class`, `RuntimeID`, that is a wrapper around an
+// RFC 4122 UUIDv4. `RuntimeID` identifies the current run of the application in
+// which this tracing library is embedded.
+//
+// See `TracerConfig::runtime_id`, declared in `tracer_config.h`.
 
 #include <string>
 
@@ -12,11 +16,11 @@ class RuntimeID {
   RuntimeID();
 
  public:
-  // Return the canonical textual representation of this ID.
+  // Return the canonical textual representation of this runtime ID.
   const std::string& string() const { return uuid_; }
 
   // Return a pseudo-randomly generated runtime ID. The underlying generator is
-  // `random_uint64()` declared in `random.h`.
+  // `random_uint64()`, declared in `random.h`.
   static RuntimeID generate();
 };
 

src/datadog/tracer_config.h

@@ -110,7 +110,11 @@ struct TracerConfig {
   // the `DD_TRACE_128_BIT_TRACEID_GENERATION_ENABLED` environment variable.
   bool trace_id_128_bit = false;
 
-  // TODO: document
+  // `runtime_id` denotes the current run of the application in which the tracer
+  // is embedded. If `runtime_id` is not specified, then it defaults to a
+  // pseudo-randomly generated value. A server that contains multiple tracers,
+  // such as those in the worker threads/processes of a reverse proxy, might
+  // specify the same `runtime_id` for all tracer instances in the same run.
   Optional<RuntimeID> runtime_id;
 };