Spring cloud sleuth: Bug (or unexpected call to internal code): parent can only be null in a local root

Question

I'm encountering a strange brave/spring-cloud-sleuth issue that only occurs when testing the application in a @SpringBootTest set up. The application makes use of a basic spring-cloud-starter-sleuth setup, no additional configuration is used other than implementing the dependency:

<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-sleuth</artifactId>
    <!-- <version>3.1.1</version> (version is derived from spring-cloud-dependencies bom) -->
</dependency>

The error that pops up every now and then during a mvn clean install:

Exception in thread "ForkJoinPool-1-worker-53" java.lang.AssertionError: Bug (or unexpected call to internal code): parent can only be null in a local root!
        at brave.internal.recorder.PendingSpans.getOrCreate(PendingSpans.java:89)
        at brave.Tracer._toSpan(Tracer.java:410)
        at brave.Tracer.toSpan(Tracer.java:382)
        at brave.Tracer.toSpan(Tracer.java:376)
        at brave.LazySpan.span(LazySpan.java:141)
        at brave.LazySpan.context(LazySpan.java:40)
        at org.springframework.cloud.sleuth.brave.bridge.BraveSpan.context(BraveSpan.java:49)
        at org.springframework.cloud.sleuth.brave.bridge.BraveTracer.nextSpan(BraveTracer.java:64)
        at org.springframework.cloud.sleuth.instrument.async.TraceRunnable.run(TraceRunnable.java:61)
        at java.base/java.util.concurrent.ForkJoinTask$RunnableExecuteAction.exec(ForkJoinTask.java:1426)
        at java.base/java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:290)
        at java.base/java.util.concurrent.ForkJoinPool$WorkQueue.topLevelExec(ForkJoinPool.java:1020)
        at java.base/java.util.concurrent.ForkJoinPool.scan(ForkJoinPool.java:1656)
        at java.base/java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1594)
        at java.base/java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:183)

Is anyone familiar with the stack trace above?

Answer 1

I found a solution almost straight after posting the question. The issue seems to be related to https://github.com/openzipkin/brave/issues/1295 . At the time of writing this post the issue has not been fixed yet.

I noticed that the error thrown is a java.lang.AssertionError, and I have disabled assertions in the package where the error occurs until a fix has been created. By configuring the maven-surefire-plugin and maven-failsafe-plugin as follows the assertion can be disabled:

<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-surefire-plugin</artifactId>
    <configuration>
        <argLine>@{argLine} -da:brave.internal.recorder...</argLine>
    </configuration>
</plugin>

<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-failsafe-plugin</artifactId>
    <configuration>
        <argLine>@{argLine} -da:brave.internal.recorder...</argLine>
    </configuration>
</plugin>