ETW example and tests clean-up

api/include/opentelemetry/context/runtime_context.h

@@ -169,7 +169,7 @@ inline Token::~Token()
 }
 
 // The ThreadLocalContextStorage class is a derived class from
-// RuntimeContextStorage and provides a wrapper for propogating context through
+// RuntimeContextStorage and provides a wrapper for propagating context through
 // cpp thread locally. This file must be included to use the RuntimeContext
 // class if another implementation has not been registered.
 class ThreadLocalContextStorage : public RuntimeContextStorage

examples/CMakeLists.txt

@@ -2,6 +2,9 @@ if(WITH_OTLP_GRPC OR WITH_OTLP_HTTP)
   add_subdirectory(otlp)
   add_subdirectory(grpc)
 endif()
+if(WITH_ETW)
+  add_subdirectory(etw_threads)
+endif()
 if(WITH_JAEGER)
   add_subdirectory(jaeger)
 endif()

examples/etw_threads/CMakeLists.txt

@@ -0,0 +1,6 @@
+project(etw_threadpool)
+
+add_executable(etw_threadpool main.cc)
+
+target_link_libraries(etw_threadpool ${CMAKE_THREAD_LIBS_INIT}
+                      opentelemetry_api opentelemetry_exporter_etw)

examples/etw_threads/README.md

@@ -0,0 +1,32 @@
+# ETW Exporter multithreaded context propagation example
+
+## Preface
+
+This example shows how to pass context from main dispatcher thread to worker threads.
+While this example is convenient to run in Visual Studio with ETW exporter, the same
+logic should apply to any other exporter. Only the initial portion that obtains ETW
+Tracer is unique to ETW, the rest can be reused.
+
+## How to debug events in Visual Studio 2019 or newer
+
+Specify your component instrumentation name, which should match the destination ETW
+Provider Name or GUID. Example uses "OpenTelemetry-ETW-TLD" for the instrument /
+instrumentation name.
+
+In Visual Studio IDE:
+
+- navigate to `View -> Other Windows -> Diagnostic Events...`
+- click `Configure...` gear on top.
+- specify `OpenTelemetry-ETW-TLD` in the list of providers to monitor.
+- run example.
+- `Diagnostic Events` view shows you the event flow in realtime.
+
+## Explanation of the code flow
+
+`main` function acts as a dispatcher to manage thread pool called `pool`. `beep_bop`
+span is started in the `main`. Then in a loop up to `kMaxThreads` get started
+concurrently. Each thread executing `beep` function with a parent scope of `main`.
+`beep` subsequently calls into `bop` function, with a parent scope of `beep` span.
+Entire execution of all threads is grouped under the main span called `beep_bop`.
+At the end of execution, the `main` function joins all pending threads and ends
+the main span.

examples/etw_threads/main.cc

@@ -0,0 +1,154 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+// Include common Trace Provider API and processor
+#include "opentelemetry/sdk/trace/simple_processor.h"
+#include "opentelemetry/sdk/trace/tracer_provider.h"
+#include "opentelemetry/trace/provider.h"
+
+#include "opentelemetry/exporters/etw/etw_tracer_exporter.h"
+
+#include <iostream>
+#include <thread>
+
+#include <cstdio>
+#ifndef LOG_DEBUG
+#  include <mutex>
+
+/**
+ * @brief Thread-safe logger routine.
+ * @param format
+ * @param args
+ * @return
+ */
+static inline int log_vprintf(const char *format, va_list args)
+{
+  static std::mutex cout_mutex;
+  std::lock_guard<std::mutex> lk(cout_mutex);
+  return vprintf(format, args);
+};
+
+/**
+ * @brief Thread-safe logger routine.
+ * @param format
+ * @param
+ * @return
+ */
+static inline int log_printf(const char *format, ...)
+{
+  int result;
+  va_list ap;
+  va_start(ap, format);
+  result = log_vprintf(format, ap);
+  va_end(ap);
+  return result;
+};
+
+// Debug macros
+#  define LOG_DEBUG(fmt_, ...) log_printf(" " fmt_ "\n", ##__VA_ARGS__)
+#  define LOG_TRACE(fmt_, ...) log_printf(" " fmt_ "\n", ##__VA_ARGS__)
+#  define LOG_INFO(fmt_, ...) log_printf(" " fmt_ "\n", ##__VA_ARGS__)
+#  define LOG_WARN(fmt_, ...) log_printf(" " fmt_ "\n", ##__VA_ARGS__)
+#  define LOG_ERROR(fmt_, ...) log_printf(" " fmt_ "\n", ##__VA_ARGS__)
+#endif
+
+using namespace OPENTELEMETRY_NAMESPACE;
+
+using namespace opentelemetry::exporter::etw;
+
+// Specify destination ETW Provider Name or GUID.
+//
+// In Visual Studio:
+// - View -> Other Windows -> Diagnostic Events...
+// - Click Configure (gear on top).
+// - Specify "OpenTelemetry-ETW-TLD" in the list of providers.
+//
+// Event view shows event flow in realtime.
+const char *kGlobalProviderName = "OpenTelemetry-ETW-TLD";
+
+std::string providerName = kGlobalProviderName;
+
+// One provider can be used to associate with different destinations.
+exporter::etw::TracerProvider provider;
+
+// Code below is generic and may be reused with any other TracerProvider.
+// In ETW provider case - instrumentation name must match destination
+// ETW provider name.
+nostd::shared_ptr<trace::Tracer> tracer = provider.GetTracer(providerName, "1.0");
+
+// Obtain numeric thread id
+static inline uint64_t gettid()
+{
+  std::stringstream ss;
+  ss << std::this_thread::get_id();
+  uint64_t id = std::stoull(ss.str());
+  return id;
+}
+
+// bop gets called by beep.
+void bop()
+{
+  LOG_TRACE("bop worker tid=%u", gettid());
+  auto span = tracer->StartSpan("bop");
+  span->AddEvent("BopEvent", {{"tid", gettid()}});
+  span->SetAttribute("attrib", 2);
+  span->End();
+}
+
+// beep gets called in its own thread.
+// It is running in a thread pool, invoked via lambda by dispatcher.
+void beep()
+{
+  LOG_TRACE("beep worker tid=%u", gettid());
+  auto span = tracer->StartSpan("beep");
+  span->AddEvent("BeepEvent", {{"tid", gettid()}});
+  span->SetAttribute("attrib", 1);
+  {
+    auto bopScope = tracer->WithActiveSpan(span);
+    bop();
+  }
+  span->End();
+}
+
+// Max number of threads to spawn
+constexpr int kMaxThreads = 10;
+
+int main(int arc, char **argv)
+{
+  std::thread pool[kMaxThreads];
+
+  // Main dispatcher span: parent of all child thread spans.
+  auto mainSpan = tracer->StartSpan("beep_bop");
+  mainSpan->SetAttribute("attrib", 0);
+
+  // Start several threads to perform beep-bop actions.
+  LOG_TRACE("beep-boop dispatcher tid=%u", gettid());
+  for (auto i = 0; i < kMaxThreads; i++)
+  {
+    pool[i] = std::thread([&]() {
+      // This code runs in its own worker thread.
+      auto beepScope = tracer->WithActiveSpan(mainSpan);
+      // call beep -> bop
+      beep();
+    });
+  };
+
+  // Join all worker threads in the pool
+  for (auto &th : pool)
+  {
+    try
+    {
+      if (th.joinable())
+        th.join();
+    }
+    catch (...)
+    {
+      // thread might have been gracefully terminated already
+    }
+  }
+
+  // End span
+  mainSpan->End();
+
+  return 0;
+}