10. Naming spans
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10. Naming spans

Picking a span name is not a trivial task. A span name should depict an operation name. The name should be low cardinality, so it should not include identifiers.

Since there is a lot of instrumentation going on, some span names are artificial:

Fortunately, for asynchronous processing, you can provide explicit naming.

10.1 @SpanName Annotation

You can name the span explicitly by using the @SpanName annotation, as shown in the following example:

	@SpanName("calculateTax")
	class TaxCountingRunnable implements Runnable {

		@Override
		public void run() {
			// perform logic
		}

	}

}

In this case, when processed in the following manner, the span is named calculateTax:

Runnable runnable = new TraceRunnable(this.tracing, spanNamer,
		new TaxCountingRunnable());
Future<?> future = executorService.submit(runnable);
// ... some additional logic ...
future.get();

10.2 toString() method

It is pretty rare to create separate classes for Runnable or Callable. Typically, one creates an anonymous instance of those classes. You cannot annotate such classes. To overcome that limitation, if there is no @SpanName annotation present, we check whether the class has a custom implementation of the toString() method.

Running such code leads to creating a span named calculateTax, as shown in the following example:

Runnable runnable = new TraceRunnable(this.tracing, spanNamer, new Runnable() {
	@Override
	public void run() {
		// perform logic
	}

	@Override
	public String toString() {
		return "calculateTax";
	}
});
Future<?> future = executorService.submit(runnable);
// ... some additional logic ...
future.get();
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9. Span lifecycle Home 11. Managing Spans with Annotations