public void preWALAppend(WALKey key, WALEdit edit) throws IOException {
    if (this.coprocEnvironments.isEmpty()) {
      return;
    }
    execOperation(new RegionObserverOperationWithoutResult() {
      @Override
      public void call(RegionObserver observer) throws IOException {
        observer.preWALAppend(this, key, edit);
      }
    });
  }
@param fs     fileystem to read from
@param p      path to the file
@param in     {@link FSDataInputStreamWrapper}
@param size   Full size of the file
@param r      original reference file. This will be not null only when reading a split file.
@param reader the base reader instance
@return The reader to use
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/RegionCoprocessorHost.java