@Override
  public boolean isDecommissionInProgress() {
    // note that, the decommission file will be removed by calling deleteStoreFiles() when replica is being dropped. We
    // don't need to explicitly delete it. The file is also used for failure recovery to resume decommission process.
    return (new File(dataDir, DECOMMISSION_FILE_NAME)).exists();
  }
@return The number of byte been written to log
ambry-store/src/main/java/com/github/ambry/store/BlobStore.java