/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.accumulo.core.file.rfile;
import java.io.PrintStream;
import java.util.ArrayList;
import java.util.Map;
import org.apache.accumulo.core.data.ByteSequence;
import org.apache.accumulo.core.data.Key;
import org.apache.accumulo.core.data.Value;
import org.apache.hadoop.io.Text;
/**
* Interface used to gather metrics from RFiles.
*
* @param <T>
* Type used to return metrics in getMetrics(). This does not impact collection of metrics at all, is only used in that method.
*/
public interface MetricsGatherer<T> {
/**
* Initialize the gatherer when it is registered with the RFile Reader
*
* @param cf
* Map of the LocalityGroup names to their column families
*/
void init(Map<String,ArrayList<ByteSequence>> cf);
/**
* Start a new LocalityGroup. This method is used when the RFile seeks to the next LocalityGroup.
*
* @param cf
* Text object of the column family of the first entry in the locality group
*/
void startLocalityGroup(Text cf);
/**
* Collect and store metrics for the given entry.
*
* @param key
* Key object of the entry you are collecting metrics from
*
* @param val
* Value object of the entry you are collecting metrics from
*
*/
void addMetric(Key key, Value val);
/**
* Start a new block within a LocalityGroup. This method is used when the RFile moves on the the next block in the LocalityGroup.
*/
void startBlock();
/**
* Print the results of the metrics gathering by locality group in the format: Metric name Number of keys Percentage of keys Number of blocks Percentage of
* blocks
*
* @param hash
* Boolean to determine whether the values being printed should be hashed
* @param metricWord
* String of the name of the metric that was collected
* @param out
* PrintStream of where the information should be written to
*/
void printMetrics(boolean hash, String metricWord, PrintStream out);
/**
* @return the metrics gathered
*/
T getMetrics();
}