@Override
  public void close() {
    if (compressor != null) {
      this.fileContext.getCompression().returnCompressor(compressor);
      compressor = null;
    }
  }
Releases the compressor this writer uses to compress blocks into the compressor pool.
hbase-common/src/main/java/org/apache/hadoop/hbase/io/encoding/HFileBlockDefaultEncodingContext.java