westonpace commented on a change in pull request #11964:
URL: https://github.com/apache/arrow/pull/11964#discussion_r771734507
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File path: cpp/src/arrow/util/tracing_internal.h
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@@ -97,6 +98,57 @@ AsyncGenerator<T> WrapAsyncGenerator(AsyncGenerator<T>
wrapped,
return fut;
};
}
+
+/// \brief Start a new span for each invocation of a generator.
+///
+/// The parent span of the new span will be the currently active span
+/// (if any) as of when WrapAsyncGenerator was itself called.
+template <typename T>
+AsyncGenerator<T> WrapAsyncGenerator(AsyncGenerator<T> wrapped,
+ const std::string& span_name) {
+ opentelemetry::trace::StartSpanOptions options;
+ options.parent = GetTracer()->GetCurrentSpan()->GetContext();
+ return WrapAsyncGenerator(std::move(wrapped), std::move(options), span_name);
+}
+
+/// \brief End the given span when the given async generator ends.
+///
+/// The span will be made the active span each time the generator is called.
+template <typename T>
+AsyncGenerator<T> TieSpanToAsyncGenerator(
+ AsyncGenerator<T> wrapped,
+ opentelemetry::nostd::shared_ptr<opentelemetry::trace::Span> span) {
+ return [=]() mutable -> Future<T> {
+ auto scope = GetTracer()->WithActiveSpan(span);
+ auto fut = wrapped();
+ fut.AddCallback([span](const Result<T>& result) {
+ if (!result.ok() || IsIterationEnd(*result)) {
+ MarkSpan(result.status(), span.get());
+ span->End();
+ }
+ });
+ return fut;
Review comment:
The order of callback can be undetermined in the event of:
```
Future<> fut = DoThing(); // Future unfinished at this point
fut.AddCallback(...); // Callback actually added
// Future finishes but callbacks haven't run yet...
fut.AddCallback(...); // Runs immediately
```
This has caused several subtle bugs and left me paranoid of `AddCallback`.
That being said, if the ordering truly doesn't matter, then it should be fine
here.
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