String appendSpanIds(List<Span> spans, StringBuilder message) {
    message.append("[");
    int i = 0;
    Iterator<Span> iterator = spans.iterator();
    while (iterator.hasNext() && i++ < 3) {
      message.append(idString(iterator.next()));
      if (iterator.hasNext()) message.append(", ");
    }
    if (iterator.hasNext()) message.append("...");

    return message.append("]").toString();
  }
When storing spans, an exception can be raised before or after the fact. This adds context of
span ids to give logs more relevance.
zipkin-collector/core/src/main/java/zipkin2/collector/Collector.java