spark CustomMetric 源码
spark CustomMetric 代码
文件路径：/sql/catalyst/src/main/java/org/apache/spark/sql/connector/metric/CustomMetric.java
/*
* 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.spark.sql.connector.metric;
import org.apache.spark.annotation.Evolving;
/**
* A custom metric. Data source can define supported custom metrics using this interface.
* During query execution, Spark will collect the task metrics using {@link CustomTaskMetric}
* and combine the metrics at the driver side. How to combine task metrics is defined by the
* metric class with the same metric name.
*
* When Spark needs to aggregate task metrics, it will internally construct the instance of
* custom metric class defined in data source by using reflection. Spark requires the class
* implementing this interface to have a 0-arg constructor.
*
* @since 3.2.0
*/
@Evolving
public interface CustomMetric {
/**
* Returns the name of custom metric.
*/
String name();
/**
* Returns the description of custom metric.
*/
String description();
/**
* The initial value of this metric.
*/
long initialValue = 0L;
/**
* Given an array of task metric values, returns aggregated final metric value.
*/
String aggregateTaskMetrics(long[] taskMetrics);
}
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