int evictToRecoverSpans(int spansToRecover) {
    int spansEvicted = 0;
    while (spansToRecover > 0) {
      int spansInOldestTrace = deleteOldestTrace();
      spansToRecover -= spansInOldestTrace;
      spansEvicted += spansInOldestTrace;
    }
    return spansEvicted;
  }
Returns the count of spans evicted.
zipkin/src/main/java/zipkin2/storage/InMemoryStorage.java