@Test void linksSpans_serverMissingParentId() {
    List<Span> trace = Arrays.asList( // to allow sorting
      span("a", null, "a", Kind.SERVER, "arn", null, false),
      span("a", "a", "b", Kind.CLIENT, "arn", "link", false),
      // below the parent ID is null as it wasn't propagated
      span("a", null, "b", Kind.SERVER, "link", "arn", false)
        .toBuilder().shared(true).build()
    );

    // trace is actually reported in reverse order
    Collections.reverse(trace);

    assertThat(new DependencyLinker().putTrace(trace).link()).containsExactly(
      DependencyLink.newBuilder().parent("arn").child("link").callCount(1L).build()
    );
  }
Some don't propagate the server's parent ID which creates a race condition. Try to unwind it.

<p>See https://github.com/openzipkin/zipkin/pull/1745
zipkin/src/test/java/zipkin2/internal/DependencyLinkerTest.java