This documentation is for an unreleased version of Apache Flink. We recommend you use the latest stable version.

Traces #

Flink exposes a tracing system that allows gathering and exposing traces to external systems.

Reporting traces #

You can access the tracing system from any user function that extends RichFunction by calling getRuntimeContext().getMetricGroup(). This method returns a MetricGroup object via which you can report a new single span trace.

Reporting single Span #

A Span represents something that happened in Flink at certain point of time, that will be reported to a TraceReporter. To report a Span you can use the MetricGroup#addSpan(SpanBuilder) method.

Currently we don’t support traces with multiple spans. Each Span is self-contained and represents things like a checkpoint or recovery.

public class MyClass {
    void doSomething() {
        // (...)
        metricGroup.addSpan(
                Span.builder(MyClass.class, "SomeAction")
                        .setStartTsMillis(startTs) // Optional
                        .setEndTsMillis(endTs) // Optional
                        .setAttribute("foo", "bar");
    }
}

Currently reporting Spans from Python is not supported.

Reporter #

For information on how to set up Flink’s trace reporters please take a look at the trace reporters documentation.

System traces #

Flink reports traces listed below.

The tables below generally feature 5 columns:

• The “Scope” column describes what is that trace reported scope.

• The “Name” column describes the name of the reported trace.

• The “Attributes” column lists the names of all attributes that are reported with the given trace.

• The “Description” column provides information as to what a given attribute is reporting.

Checkpointing and initialization #

Flink reports a single span trace for the whole checkpoint and job initialization events once that event reaches a terminal state: COMPLETED or FAILED.

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