commonlib/src/main/java/com/streamsets/pipeline/lib/io/MultiFileReader.java
public Map<String, Long> getOffsetsLag(Map<String, String> offsetMap) throws IOException{
    return fileContextProvider.getOffsetsLag(offsetMap);
  }
public Map<String, Long> getOffsetsLag(Map<String, String> offsetMap) throws IOException{
    return fileContextProvider.getOffsetsLag(offsetMap);
  }
Determines the offset lag for each active file being read.

@param offsetMap the current Offset for file keys.
@return map of fileKey to offset.