org.apache.hadoop.fs.statistics.IOStatisticsSupport Maven / Gradle / Ivy
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* 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.hadoop.fs.statistics;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.fs.statistics.impl.StubDurationTracker;
import org.apache.hadoop.fs.statistics.impl.StubDurationTrackerFactory;
/**
* Support for working with IOStatistics.
*/
@InterfaceAudience.Public
@InterfaceStability.Unstable
public final class IOStatisticsSupport {
private IOStatisticsSupport() {
}
/**
* Take a snapshot of the current statistics state.
*
* This is not an atomic option.
*
* The instance can be serialized, and its
* {@code toString()} method lists all the values.
* @param statistics statistics
* @return a snapshot of the current values.
*/
public static IOStatisticsSnapshot
snapshotIOStatistics(IOStatistics statistics) {
return new IOStatisticsSnapshot(statistics);
}
/**
* Create a snapshot statistics instance ready to aggregate data.
*
* The instance can be serialized, and its
* {@code toString()} method lists all the values.
* @return an empty snapshot
*/
public static IOStatisticsSnapshot
snapshotIOStatistics() {
return new IOStatisticsSnapshot();
}
/**
* Get the IOStatistics of the source, casting it
* if it is of the relevant type, otherwise,
* if it implements {@link IOStatisticsSource}
* extracting the value.
*
* Returns null if the source isn't of the write type
* or the return value of
* {@link IOStatisticsSource#getIOStatistics()} was null.
* @return an IOStatistics instance or null
*/
public static IOStatistics retrieveIOStatistics(
final Object source) {
if (source instanceof IOStatistics) {
return (IOStatistics) source;
} else if (source instanceof IOStatisticsSource) {
return ((IOStatisticsSource) source).getIOStatistics();
} else {
// null source or interface not implemented
return null;
}
}
/**
* Return a stub duration tracker factory whose returned trackers
* are always no-ops.
*
* As singletons are returned, this is very low-cost to use.
* @return a duration tracker factory.
*/
public static DurationTrackerFactory stubDurationTrackerFactory() {
return StubDurationTrackerFactory.STUB_DURATION_TRACKER_FACTORY;
}
/**
* Get a stub duration tracker.
* @return a stub tracker.
*/
public static DurationTracker stubDurationTracker() {
return StubDurationTracker.STUB_DURATION_TRACKER;
}
}