com.google.cloud.dataflow.sdk.util.common

Class Counter<T>

java.lang.Object

com.google.cloud.dataflow.sdk.util.common.Counter<T>

Type Parameters:

T - the type of values aggregated by this counter

public abstract class Counter<T>
extends Object

A Counter enables the aggregation of a stream of values over time. The cumulative aggregate value is updated as new values are added, or it can be reset to a new value. Multiple kinds of aggregation are supported depending on the type of the counter.

Counters compare using value equality of their name, kind, and cumulative value. Equal counters should have equal toString()s.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	Counter.AggregationKind Possible kinds of counter aggregation.
static interface	Counter.CounterMean<T> The mean value of a Counter, represented as an aggregate value and a count.

Field Summary

Fields

Modifier and Type	Field and Description
protected Counter.AggregationKind	kind The kind of aggregation function to apply to this counter.
protected String	name The name of this counter.

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	Counter(String name, Counter.AggregationKind kind)

Method Summary

Modifier and Type	Method and Description
abstract Counter<T>	addValue(T value) Adds a new value to the aggregation stream.
static Counter<Boolean>	booleans(String name, Counter.AggregationKind kind) Constructs a new Counter that aggregates Boolean values according to the desired aggregation kind.
static Counter<Double>	doubles(String name, Counter.AggregationKind kind) Constructs a new Counter that aggregates Double values according to the desired aggregation kind.
boolean	equals(Object o)
abstract T	getAggregate() Returns the aggregated value, or the sum for MEAN aggregation, either total or, if delta, since the last update extraction or resetDelta.
abstract T	getAndResetDelta() Resets the counter's delta value to have no values accumulated and returns the value of the delta prior to the reset.
abstract Counter.CounterMean<T>	getAndResetMeanDelta() Resets the counter's delta value to have no values accumulated and returns the value of the delta prior to the reset, for a MEAN counter.
Counter.AggregationKind	getKind() Returns the counter's aggregation kind.
abstract Counter.CounterMean<T>	getMean() Returns the mean in the form of a CounterMean, or null if this is not a MEAN counter.
String	getName() Returns the counter's name.
Class<?>	getType() Returns the counter's type.
int	hashCode()
protected IllegalArgumentException	illegalArgumentException() Constructs an IllegalArgumentException explaining that this Counter's aggregation kind is not supported by its value type.
static Counter<Integer>	ints(String name, Counter.AggregationKind kind) Constructs a new Counter that aggregates Integer, values according to the desired aggregation kind.
boolean	isCompatibleWith(Counter<?> that) Returns whether this Counter is compatible with that Counter.
static Counter<Long>	longs(String name, Counter.AggregationKind kind) Constructs a new Counter that aggregates Long values according to the desired aggregation kind.
abstract Counter<T>	resetMeanToValue(long elementCount, T value) Resets the aggregation stream to this new value.
abstract Counter<T>	resetToValue(T value) Resets the aggregation stream to this new value.
String	toString() Returns a string representation of the Counter.

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

name

protected final String name

The name of this counter.

kind

protected final Counter.AggregationKind kind

The kind of aggregation function to apply to this counter.

Constructor Detail

Counter

protected Counter(String name,
                  Counter.AggregationKind kind)

Method Detail

ints

public static Counter<Integer> ints(String name,
                                    Counter.AggregationKind kind)

Constructs a new Counter that aggregates Integer, values according to the desired aggregation kind. The supported aggregation kinds are Counter.AggregationKind.SUM, Counter.AggregationKind.MIN, Counter.AggregationKind.MAX, and Counter.AggregationKind.MEAN. This is a convenience wrapper over a Counter implementation that aggregates Long values. This is useful when the application handles (boxed) Integer values that are not readily convertible to the (boxed) Long values otherwise expected by the Counter implementation aggregating Long values.

Parameters:

name - the name of the new counter

kind - the new counter's aggregation kind

Returns:

the newly constructed Counter

Throws:

IllegalArgumentException - if the aggregation kind is not supported

longs

public static Counter<Long> longs(String name,
                                  Counter.AggregationKind kind)

Constructs a new Counter that aggregates Long values according to the desired aggregation kind. The supported aggregation kinds are Counter.AggregationKind.SUM, Counter.AggregationKind.MIN, Counter.AggregationKind.MAX, and Counter.AggregationKind.MEAN.

Parameters:

name - the name of the new counter

kind - the new counter's aggregation kind

Returns:

the newly constructed Counter

Throws:

IllegalArgumentException - if the aggregation kind is not supported

doubles

public static Counter<Double> doubles(String name,
                                      Counter.AggregationKind kind)

Constructs a new Counter that aggregates Double values according to the desired aggregation kind. The supported aggregation kinds are Counter.AggregationKind.SUM, Counter.AggregationKind.MIN, Counter.AggregationKind.MAX, and Counter.AggregationKind.MEAN.

Parameters:

name - the name of the new counter

kind - the new counter's aggregation kind

Returns:

the newly constructed Counter

Throws:

IllegalArgumentException - if the aggregation kind is not supported

booleans

public static Counter<Boolean> booleans(String name,
                                        Counter.AggregationKind kind)

Constructs a new Counter that aggregates Boolean values according to the desired aggregation kind. The only supported aggregation kinds are Counter.AggregationKind.AND and Counter.AggregationKind.OR.

Parameters:

name - the name of the new counter

kind - the new counter's aggregation kind

Returns:

the newly constructed Counter

Throws:

IllegalArgumentException - if the aggregation kind is not supported

addValue

public abstract Counter<T> addValue(T value)

Adds a new value to the aggregation stream. Returns this (to allow method chaining).

resetToValue

public abstract Counter<T> resetToValue(T value)

Resets the aggregation stream to this new value. This aggregator must not be a MEAN aggregator. Returns this (to allow method chaining).

resetMeanToValue

public abstract Counter<T> resetMeanToValue(long elementCount,
                                            T value)

Resets the aggregation stream to this new value. Returns this (to allow method chaining). The value of elementCount must be non-negative, and this aggregator must be a MEAN aggregator.

getAndResetDelta

public abstract T getAndResetDelta()

Resets the counter's delta value to have no values accumulated and returns the value of the delta prior to the reset.

Returns:

the aggregate delta at the time this method is called

getAndResetMeanDelta

public abstract Counter.CounterMean<T> getAndResetMeanDelta()

Resets the counter's delta value to have no values accumulated and returns the value of the delta prior to the reset, for a MEAN counter.

Returns:

the mean delta t the time this method is called

getName

public String getName()

Returns the counter's name.

getKind

public Counter.AggregationKind getKind()

Returns the counter's aggregation kind.

getType

public Class<?> getType()

Returns the counter's type.

getAggregate

public abstract T getAggregate()

Returns the aggregated value, or the sum for MEAN aggregation, either total or, if delta, since the last update extraction or resetDelta.

getMean

@Nullable
public abstract Counter.CounterMean<T> getMean()

Returns the mean in the form of a CounterMean, or null if this is not a MEAN counter.

toString

public String toString()

Returns a string representation of the Counter. Useful for debugging logs. Example return value: "ElementCount:SUM(15)".

Overrides:

toString in class Object

equals

public boolean equals(Object o)

Overrides:

equals in class Object

hashCode

public int hashCode()

Overrides:

hashCode in class Object

isCompatibleWith

public boolean isCompatibleWith(Counter<?> that)

Returns whether this Counter is compatible with that Counter. If so, they can be merged into a single Counter.

illegalArgumentException

protected IllegalArgumentException illegalArgumentException()

Constructs an IllegalArgumentException explaining that this Counter's aggregation kind is not supported by its value type.