Package org.HdrHistogram

Class HistogramLogWriter

java.lang.Object

org.HdrHistogram.HistogramLogWriter

public class HistogramLogWriter
extends Object

A histogram log writer.

A Histogram logs are used to capture full fidelity, per-time-interval histograms of a recorded value.

For example, a histogram log can be used to capture high fidelity reaction-time logs for some measured system or subsystem component. Such a log would capture a full reaction time histogram for each logged interval, and could be used to later reconstruct a full HdrHistogram of the measured reaction time behavior for any arbitrary time range within the log, by adding [only] the relevant interval histograms.

This log writer will produce histogram logs that adhere to the histogram log format (see {HistogramLogReader for log format details). Optional comments, start time, legend, and format version can be logged.

The log writer will use the

By convention, it is typical for the logging application to use a comment to indicate the logging application at the head of the log, followed by the log format version, a start time, and a legend (in that order).

Constructor Summary

Constructors

Constructor	Description
HistogramLogWriter(File outputFile)	Constructs a new HistogramLogWriter that will write into the specified file.
HistogramLogWriter(OutputStream outputStream)	Constructs a new HistogramLogWriter that will write into the specified output stream.
HistogramLogWriter(PrintStream printStream)	Constructs a new HistogramLogWriter that will write into the specified print stream.
HistogramLogWriter(String outputFileName)	Constructs a new HistogramLogWriter around a newly created file with the specified file name.

Method Summary

Modifier and Type	Method	Description
void	close()	Closes the file or output stream for this log writer.
long	getBaseTime()	return the current base time offset (see setBaseTime(long)).
void	outputBaseTime(long baseTimeMsec)	Log a base time in the log.
void	outputComment(String comment)	Log a comment to the log.
void	outputIntervalHistogram(double startTimeStampSec, double endTimeStampSec, EncodableHistogram histogram)	Output an interval histogram, with the given timestamp information, and the [optional] tag associated with the histogram.
void	outputIntervalHistogram(double startTimeStampSec, double endTimeStampSec, EncodableHistogram histogram, double maxValueUnitRatio)	Output an interval histogram, with the given timestamp information and the [optional] tag associated with the histogram, using a configurable maxValueUnitRatio.
void	outputIntervalHistogram(EncodableHistogram histogram)	Output an interval histogram, using the start/end timestamp indicated in the histogram, and the [optional] tag associated with the histogram.
void	outputLegend()	Output a legend line to the log.
void	outputLogFormatVersion()	Output a log format version to the log.
void	outputStartTime(long startTimeMsec)	Log a start time in the log.
void	setBaseTime(long baseTimeMsec)	Set a base time to subtract from supplied histogram start/end timestamps when logging based on histogram timestamps.

Methods inherited from class java.lang.Object

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

Constructor Detail

HistogramLogWriter

public HistogramLogWriter(String outputFileName)
                   throws FileNotFoundException

Constructs a new HistogramLogWriter around a newly created file with the specified file name.

Parameters:

outputFileName - The name of the file to create

Throws:

FileNotFoundException - when unable to open outputFileName

HistogramLogWriter

public HistogramLogWriter(File outputFile)
                   throws FileNotFoundException

Constructs a new HistogramLogWriter that will write into the specified file.

Parameters:

outputFile - The File to write to

Throws:

FileNotFoundException - when unable to open outputFile

HistogramLogWriter

public HistogramLogWriter(OutputStream outputStream)

Constructs a new HistogramLogWriter that will write into the specified output stream.

Parameters:

outputStream - The OutputStream to write to

HistogramLogWriter

public HistogramLogWriter(PrintStream printStream)

Constructs a new HistogramLogWriter that will write into the specified print stream.

Parameters:

printStream - The PrintStream to write to

Method Detail

close

public void close()

Closes the file or output stream for this log writer.

outputIntervalHistogram

public void outputIntervalHistogram(double startTimeStampSec,
                                    double endTimeStampSec,
                                    EncodableHistogram histogram,
                                    double maxValueUnitRatio)

Output an interval histogram, with the given timestamp information and the [optional] tag associated with the histogram, using a configurable maxValueUnitRatio. (note that the specified timestamp information will be used, and the timestamp information in the actual histogram will be ignored). The max value reported with the interval line will be scaled by the given maxValueUnitRatio.

Parameters:

startTimeStampSec - The start timestamp to log with the interval histogram, in seconds.

endTimeStampSec - The end timestamp to log with the interval histogram, in seconds.

histogram - The interval histogram to log.

maxValueUnitRatio - The ratio by which to divide the histogram's max value when reporting on it.

outputIntervalHistogram

public void outputIntervalHistogram(double startTimeStampSec,
                                    double endTimeStampSec,
                                    EncodableHistogram histogram)

Output an interval histogram, with the given timestamp information, and the [optional] tag associated with the histogram. (note that the specified timestamp information will be used, and the timestamp information in the actual histogram will be ignored). The max value in the histogram will be reported scaled down by a default maxValueUnitRatio of 1,000,000 (which is the msec : nsec ratio). Caller should use the direct form specifying maxValueUnitRatio some other ratio is needed for the max value output.

Parameters:

startTimeStampSec - The start timestamp to log with the interval histogram, in seconds.

endTimeStampSec - The end timestamp to log with the interval histogram, in seconds.

histogram - The interval histogram to log.

outputIntervalHistogram

public void outputIntervalHistogram(EncodableHistogram histogram)

Output an interval histogram, using the start/end timestamp indicated in the histogram, and the [optional] tag associated with the histogram. The histogram start and end timestamps are assumed to be in msec units. Logging will be in seconds, realtive by a base time (if set via setBaseTime(long)). The default base time is 0.

By covention, histogram start/end time are generally stamped with absolute times in msec since the epoch. For logging with absolute time stamps, the base time would remain zero. For logging with relative time stamps (time since a start point), the base time should be set with setBaseTime(long).

The max value in the histogram will be reported scaled down by a default maxValueUnitRatio of 1,000,000 (which is the msec : nsec ratio). Caller should use the direct form specifying maxValueUnitRatio if some other ratio is needed for the max value output.

Parameters:

histogram - The interval histogram to log.

outputStartTime

public void outputStartTime(long startTimeMsec)

Log a start time in the log.

Parameters:

startTimeMsec - time (in milliseconds) since the absolute start time (the epoch)

outputBaseTime

public void outputBaseTime(long baseTimeMsec)

Log a base time in the log.

Parameters:

baseTimeMsec - time (in milliseconds) since the absolute start time (the epoch)

outputComment

public void outputComment(String comment)

Log a comment to the log. Comments will be preceded with with the '#' character.

Parameters:

comment - the comment string.

outputLegend

public void outputLegend()

Output a legend line to the log.

outputLogFormatVersion

public void outputLogFormatVersion()

Output a log format version to the log.

setBaseTime

public void setBaseTime(long baseTimeMsec)

Set a base time to subtract from supplied histogram start/end timestamps when logging based on histogram timestamps. Base time is expected to be in msec since the epoch, as histogram start/end times are typically stamped with absolute times in msec since the epoch.

Parameters:

baseTimeMsec - base time to calculate timestamp deltas from

getBaseTime

public long getBaseTime()

return the current base time offset (see setBaseTime(long)).

Returns:

the current base time