@Override
  public boolean isDeviceAlive(IDeviceID device, long ttl) {
    return ttl == Long.MAX_VALUE
        || endTimes[deviceToIndex.get(device)] >= CommonDateTimeUtils.currentTime() - ttl;
  }
Deserialize TimeIndex and get devices only.

@param inputStream inputStream
@return device name
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/storageengine/dataregion/tsfile/timeindex/ArrayDeviceTimeIndex.java