@Test @Timeout(3000L) void doesntHangWhenAllDown() {
    TestPropertyValues.of(
      "spring.config.name=zipkin-server",
      "zipkin.storage.type:elasticsearch",
      "zipkin.storage.elasticsearch.timeout:1000",
      "zipkin.storage.elasticsearch.hosts:127.0.0.1:1234,127.0.0.1:5678")
      .applyTo(context);
    Access.registerElasticsearch(context);
    context.refresh();

    try (ElasticsearchStorage storage = context.getBean(ElasticsearchStorage.class)) {
      CheckResult result = storage.check();
      assertThat(result.ok()).isFalse();
    }
  }
blocking a little is ok, but blocking forever is not.
zipkin-server/src/test/java/zipkin2/server/internal/elasticsearch/ITElasticsearchClientInitialization.java