@Override public boolean isOverCapacity(Throwable e) {
    return e instanceof RejectedExecutionException || e instanceof ResponseTimeoutException;
  }
Internal code and api responses coerce to {@link RejectedExecutionException} when work is
rejected. We also classify {@link ResponseTimeoutException} as a capacity related exception
even though capacity is not the only reason (timeout could also result from a misconfiguration
or a network problem).
zipkin-storage/elasticsearch/src/main/java/zipkin2/elasticsearch/ElasticsearchStorage.java