org.apache.hadoop.fs.statistics

Class IOStatisticsSnapshot

java.lang.Object

org.apache.hadoop.fs.statistics.IOStatisticsSnapshot

All Implemented Interfaces:

Serializable, IOStatistics, IOStatisticsAggregator

@InterfaceAudience.Public
 @InterfaceStability.Evolving
public final class IOStatisticsSnapshot
extends Object
implements IOStatistics, Serializable, IOStatisticsAggregator

Snapshot of statistics from a different source.

It is serializable so that frameworks which can use java serialization to propagate data (Spark, Flink...) can send the statistics back. For this reason, TreeMaps are explicitly used as field types, even though IDEs can recommend use of Map instead. For security reasons, untrusted java object streams should never be deserialized. If for some reason this is required, use requiredSerializationClasses() to get the list of classes used when deserializing instances of this object.

It is annotated for correct serializations with jackson2.

See Also:

Serialized Form

Field Summary

Fields inherited from interface org.apache.hadoop.fs.statistics.IOStatistics

MAX_UNSET_VALUE, MIN_UNSET_VALUE

Constructor Summary

Constructors

Constructor and Description
IOStatisticsSnapshot() Construct.
IOStatisticsSnapshot(IOStatistics source) Construct, taking a snapshot of the source statistics data if the source is non-null.

Method Summary

Modifier and Type	Method and Description
boolean	aggregate(IOStatistics source) Aggregate the current statistics with the source reference passed in.
void	clear() Clear all the maps.
Map<String,Long>	counters() Map of counters.
Map<String,Long>	gauges() Map of gauges.
Map<String,Long>	maximums() Map of maximums.
Map<String,MeanStatistic>	meanStatistics() Map of meanStatistics.
Map<String,Long>	minimums() Map of minimums.
static List<Class>	requiredSerializationClasses() What classes are needed to deserialize this class? Needed to securely unmarshall this from untrusted sources.
static org.apache.hadoop.util.JsonSerialization<IOStatisticsSnapshot>	serializer() Get a JSON serializer for this class.
void	snapshot(IOStatistics source) Take a snapshot.
String	toString()

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

IOStatisticsSnapshot

public IOStatisticsSnapshot()

Construct.

IOStatisticsSnapshot

public IOStatisticsSnapshot(IOStatistics source)

Construct, taking a snapshot of the source statistics data if the source is non-null. If the source is null, the empty maps are created

Parameters:

source - statistics source. Nullable.

Method Detail

clear

public void clear()

Clear all the maps.

snapshot

public void snapshot(IOStatistics source)

Take a snapshot. This completely overwrites the map data with the statistics from the source.

Parameters:

source - statistics source.

aggregate

public boolean aggregate(@Nullable
                         IOStatistics source)

Aggregate the current statistics with the source reference passed in. The operation is synchronized.

Specified by:

aggregate in interface IOStatisticsAggregator

Parameters:

source - source; may be null

Returns:

true if a merge took place.

counters

public Map<String,Long> counters()

Description copied from interface: IOStatistics

Map of counters.

Specified by:

counters in interface IOStatistics

Returns:

the current map of counters.

gauges

public Map<String,Long> gauges()

Description copied from interface: IOStatistics

Map of gauges.

Specified by:

gauges in interface IOStatistics

Returns:

the current map of gauges.

minimums

public Map<String,Long> minimums()

Description copied from interface: IOStatistics

Map of minimums.

Specified by:

minimums in interface IOStatistics

Returns:

the current map of minimums.

maximums

public Map<String,Long> maximums()

Description copied from interface: IOStatistics

Map of maximums.

Specified by:

maximums in interface IOStatistics

Returns:

the current map of maximums.

meanStatistics

public Map<String,MeanStatistic> meanStatistics()

Description copied from interface: IOStatistics

Map of meanStatistics.

Specified by:

meanStatistics in interface IOStatistics

Returns:

the current map of MeanStatistic statistics.

toString

public String toString()

Overrides:

toString in class Object

serializer

public static org.apache.hadoop.util.JsonSerialization<IOStatisticsSnapshot> serializer()

Get a JSON serializer for this class.

Returns:

a serializer.

requiredSerializationClasses

public static List<Class> requiredSerializationClasses()

What classes are needed to deserialize this class? Needed to securely unmarshall this from untrusted sources.

Returns:

a list of required classes to deserialize the data.