ZeroTierOne/ext/opentelemetry-cpp-1.21.0/examples/etw_threads

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.