View Traces in Jaeger

In recent Jaeger versions, OTLP is supported natively. This means we can send traces to it directly without OpenTelemetry Collector in the middle.

Let's review the example provided in README first.

using OpenTelemetry
using Term # optional, for better display

global_tracer_provider(TracerProvider());

Here we set a TracerProvider as the global_tracer_provider. One argument we omitted when constructing TracerProvider is the span_processor. Its default value is SimpleSpanProcessor(ConsoleExporter()). By default, it will redirect all the spans to console.

with_span("Hello, World!") do
    with_span("from") do
        @info "OpenTelemetry.jl!"
    end
end

In the above code, two spans are created. As you can see, the span context of these two spans are correlated. The trace_id and span_id in the OpenTelemetry.jl! log record is also associated with the inner span of from.

Export Spans to Jaeger

Let's setup the Jaeger first:

cd docs/src/tutorials/View_Traces_in_Jaeger
docker compose up

Then we replace the original ConsoleExporter with OtlpHttpTracesExporter.

global_tracer_provider(TracerProvider(;span_processor=SimpleSpanProcessor(OtlpHttpTracesExporter())))

with_span("Hello, World!") do
    with_span("from") do
        @info "OpenTelemetry.jl!"
    end
end

Now open the Jaeger web portal at http://localhost:16686/. You should find a trace with the name of unknown_service:julia: Hello, World! by filtering the service. After clicking the Find Traces button, you should see the detailed spans like the the screenshot below.

Reduce the Time Cost with BatchSpanProcessor

Note that with SimpleSpanProcessor, we're actually sending spans to the Jaeger immediately at the end of each span. To reduce the overall time cost, we can replace it with BatchSpanProcessor.

global_tracer_provider(TracerProvider(;span_processor=BatchSpanProcessor(OtlpHttpTracesExporter())))

with_span("Hello, World!") do
    with_span("from") do
        @info "OpenTelemetry.jl!"
    end
end