com.aquenos.cassandra.pvarchiver.controlsystem

Class AbstractStatefulSampleDecimator<SampleType extends Sample>

java.lang.Object

com.aquenos.cassandra.pvarchiver.controlsystem.AbstractSampleDecimator<SampleType>

com.aquenos.cassandra.pvarchiver.controlsystem.AbstractStatefulSampleDecimator<SampleType>

Type Parameters:

SampleType - type that is implemented by all samples that are passed to this sample decimator and that is also implemented by the sample generated by this sample decimator. Typically, this is the sample type used by the control-system support that provides the concrete implementation that inherits from this base class.

All Implemented Interfaces:

SampleDecimator<SampleType>

public abstract class AbstractStatefulSampleDecimator<SampleType extends Sample>
extends AbstractSampleDecimator<SampleType>

Abstract base class for sample decimator implementations, handling some of the state management. In addition to storing the channel name and the interval start time and length, this class takes care of handling some of the state when processing samples.

Each sample passed to this class's processSample(Sample) method is forwarded to the processSampleInternal(Sample, long, long) method, adding the start and end time of the interval for which this sample should be used. Usually, the start time is the time also specified by the sample and the end time is the time specified by the next sample. However, when processing the first sample, the start time is the start time of the interval that is covered by this decimator. Consequently, when processing the last sample, the end time is the end time of the interval covered by this decimator.

The buildDecimatedSample() method forwards to the buildDecimatedSampleInternal() method because it has to make a last call to processSampleInternal(Sample, long, long) for the last sample that has been received but not processed yet.

Author:

Sebastian Marsching

Constructor Summary

Constructors

Constructor and Description
AbstractStatefulSampleDecimator(String channelName, long intervalStartTime, long intervalLength) Creates the sample decimator and initializes the channel name and the interval start-time and length with the specified values.

Method Summary

Modifier and Type	Method and Description
void	buildDecimatedSample() Builds the decimated sample.
protected abstract void	buildDecimatedSampleInternal() Builds the decimated sample.
void	processSample(SampleType sample) Processes a sample, updating the internal state with the information from the sample.
protected abstract void	processSampleInternal(SampleType sample, long startTime, long endTime) Processes a sample, updating the decimators internal state.

Methods inherited from class com.aquenos.cassandra.pvarchiver.controlsystem.AbstractSampleDecimator

getChannelName, getIntervalLength, getIntervalStartTime

Methods inherited from class java.lang.Object

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

Methods inherited from interface com.aquenos.cassandra.pvarchiver.controlsystem.SampleDecimator

getDecimatedSample, getDecimatedSampleEstimatedSize

Constructor Detail

AbstractStatefulSampleDecimator

public AbstractStatefulSampleDecimator(String channelName,
                                       long intervalStartTime,
                                       long intervalLength)

Creates the sample decimator and initializes the channel name and the interval start-time and length with the specified values.

Parameters:

channelName - name identifying the channel covered by this sample decimator.

intervalStartTime - start time of the interval covered by this sample decimator. The time is specified as the number of nanoseconds since epoch (January 1st, 1970, 00:00:00 UTC).

intervalLength - length of the interval covered by this sample decimator. The length is specified in nanoseconds.

Method Detail

buildDecimatedSample

public final void buildDecimatedSample()

Description copied from interface: SampleDecimator

Builds the decimated sample. This method must only be called after SampleDecimator.processSample(Sample) has been called at least once. It must be called before calling SampleDecimator.getDecimatedSample() or SampleDecimator.getDecimatedSampleEstimatedSize(). SampleDecimator.processSample(Sample) must not be called again after calling this method and this method must only be called once. This method may throw an IllegalStateException if the specified call order is violated. However, there is no guarantee that such an exception is thrown.

processSample

public final void processSample(SampleType sample)

Description copied from interface: SampleDecimator

Processes a sample, updating the internal state with the information from the sample. This method must be called for every sample that is is in the interval specified by the start time and length (as returned by SampleDecimator.getIntervalStartTime() and SampleDecimator.getIntervalLength()).

The first sample passed to this method must have a time stamp that is less than or equal to the interval start-time. This method must be called at least once before calling SampleDecimator.buildDecimatedSample(). It must not be called after calling SampleDecimator.buildDecimatedSample(). This method may throw an IllegalStateException if the specified call order is violated. However, there is no guarantee that such an exception is thrown.

Parameters:

sample - sample that shall be processed, updating the sample decimator's internal state.

buildDecimatedSampleInternal

protected abstract void buildDecimatedSampleInternal()

Builds the decimated sample. This method has to be implemented by child classes in order to calculate the sample that is subsequently returned by SampleDecimator.getDecimatedSample(). This method is only called once and only after all calls to processSampleInternal(Sample, long, long) have been made.

processSampleInternal

protected abstract void processSampleInternal(SampleType sample,
                                              long startTime,
                                              long endTime)

Processes a sample, updating the decimators internal state. This method has to be implemented by child classes in order to process source samples. The specified start time is the start of the interval for which the specified sample should be used (inclusive). The specified end time is the end of the interval for which the specified sample should be used (exclusive). Both times are specified as the number of nanoseconds since epoch (January 1st, 1970, 00:00:00 UTC).

Usually, the start time is the time also specified by the sample and the end time is the time specified by the next sample. However, when processing the first sample, the start time is the start time of the interval that is covered by this decimator. Consequently, when processing the last sample, the end time is the end time of the interval covered by this decimator.

Parameters:

sample - sample that shall be processed.

startTime - start time of the interval for which the specified sample shall be used.

endTime - end time of the interval for which the specified sample shall be used.