@Override
  public void appendFrom(ReadableByteChannel channel, long size) throws StoreException {
    rollOverIfRequired(size);
    activeSegment.appendFrom(channel, size);
  }
Appends the given data to the active log segment. The data will be written to a single log segment i.e. the data
will not exist across segments.
@param channel The channel from which data needs to be written from
@param size The amount of data in bytes to be written from the channel
@throws IllegalArgumentException if the {@code size} is greater than a single segment's size.
@throws IllegalStateException if there no more capacity in the log.
@throws StoreException if there was a store exception while writing.
ambry-store/src/main/java/com/github/ambry/store/Log.java