package org.HdrHistogram_voltpatches;
import javax.xml.bind.DatatypeConverter;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.OutputStream;
import java.io.PrintStream;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.util.Arrays;
import java.util.Date;
import java.util.Locale;
import java.util.zip.Deflater;
import static java.nio.ByteOrder.BIG_ENDIAN;
/**
* A histogram log writer.
* <p>
* A Histogram logs are used to capture full fidelity, per-time-interval
* histograms of a recorded value.
* <p>
* 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.
* <p>
* This log writer will produce histogram logs that adhere to the
* histogram log format (see {{@link HistogramLogReader} for log format
* details). Optional comments, start time, legend, and format version
* can be logged.
* <p>
* 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).
*
*/
public class HistogramLogWriter {
private static final String HISTOGRAM_LOG_FORMAT_VERSION = "1.2";
private final PrintStream log;
private ByteBuffer targetBuffer;
private long baseTime = 0;
/**
* Constructs a new HistogramLogWriter around a newly created file with the specified file name.
* @param outputFileName The name of the file to create
* @throws FileNotFoundException when unable to open outputFileName
*/
public HistogramLogWriter(final String outputFileName) throws FileNotFoundException {
log = new PrintStream(outputFileName);
}
/**
* Constructs a new HistogramLogWriter that will write into the specified file.
* @param outputFile The File to write to
* @throws FileNotFoundException when unable to open outputFile
*/
public HistogramLogWriter(final File outputFile) throws FileNotFoundException {
log = new PrintStream(outputFile);
}
/**
* Constructs a new HistogramLogWriter that will write into the specified output stream.
* @param outputStream The OutputStream to write to
*/
public HistogramLogWriter(final OutputStream outputStream) {
log = new PrintStream(outputStream);
}
/**
* Constructs a new HistogramLogWriter that will write into the specified print stream.
* @param printStream The PrintStream to write to
*/
public HistogramLogWriter(final PrintStream printStream) {
log = printStream;
}
/**
* Output an interval histogram, with the given timestamp and a configurable maxValueUnitRatio.
* (note that the specified timestamp will be used, and the timestamp in the actual
* histogram will be ignored).
* The max value reported with the interval line will be scaled by the given maxValueUnitRatio.
* @param startTimeStampSec The start timestamp to log with the interval histogram, in seconds.
* @param endTimeStampSec The end timestamp to log with the interval histogram, in seconds.
* @param histogram The interval histogram to log.
* @param maxValueUnitRatio The ratio by which to divide the histogram's max value when reporting on it.
*/
public void outputIntervalHistogram(final double startTimeStampSec,
final double endTimeStampSec,
final EncodableHistogram histogram,
final double maxValueUnitRatio) {
if ((targetBuffer == null) || targetBuffer.capacity() < histogram.getNeededByteBufferCapacity()) {
targetBuffer = ByteBuffer.allocate(histogram.getNeededByteBufferCapacity()).order(BIG_ENDIAN);
}
targetBuffer.clear();
int compressedLength = histogram.encodeIntoCompressedByteBuffer(targetBuffer, Deflater.BEST_COMPRESSION);
byte[] compressedArray = Arrays.copyOf(targetBuffer.array(), compressedLength);
log.format(Locale.US, "%.3f,%.3f,%.3f,%s\n",
startTimeStampSec,
endTimeStampSec - startTimeStampSec,
histogram.getMaxValueAsDouble() / maxValueUnitRatio,
DatatypeConverter.printBase64Binary(compressedArray)
);
}
/**
* Output an interval histogram, with the given timestamp.
* (note that the specified timestamp will be used, and the timestamp 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.
* @param startTimeStampSec The start timestamp to log with the interval histogram, in seconds.
* @param endTimeStampSec The end timestamp to log with the interval histogram, in seconds.
* @param histogram The interval histogram to log.
*/
public void outputIntervalHistogram(final double startTimeStampSec,
final double endTimeStampSec,
final EncodableHistogram histogram) {
outputIntervalHistogram(startTimeStampSec, endTimeStampSec, histogram, 1000000.0);
}
/**
* Output an interval histogram, using the start/end timestamp indicated in 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 {@link org.HdrHistogram_voltpatches.HdrHistogram.HistogramLogWriter#setBaseTime}).
* The default base time is 0.
* <p>
* 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 {@link org.HdrHistogram_voltpatches.HdrHistogram.HistogramLogWriter#setBaseTime}.
* <p>
* 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.
* @param histogram The interval histogram to log.
*/
public void outputIntervalHistogram(final EncodableHistogram histogram) {
outputIntervalHistogram((histogram.getStartTimeStamp() - baseTime)/1000.0,
(histogram.getEndTimeStamp() - baseTime)/1000.0,
histogram);
}
/**
* Log a start time in the log.
* @param startTimeMsec time (in milliseconds) since the absolute start time (the epoch)
*/
public void outputStartTime(final long startTimeMsec) {
log.format(Locale.US, "#[StartTime: %.3f (seconds since epoch), %s]\n",
startTimeMsec / 1000.0,
(new Date(startTimeMsec)).toString());
}
/**
* Log a base time in the log.
* @param baseTimeMsec time (in milliseconds) since the absolute start time (the epoch)
*/
public void outputBaseTime(final long baseTimeMsec) {
log.format(Locale.US, "#[BaseTime: %.3f (seconds since epoch)]\n",
baseTimeMsec/1000.0);
}
/**
* Log a comment to the log.
* Comments will be preceded with with the '#' character.
* @param comment the comment string.
*/
public void outputComment(final String comment) {
log.format("#%s\n", comment);
}
/**
* Output a legend line to the log.
*/
public void outputLegend() {
log.println("\"StartTimestamp\",\"Interval_Length\",\"Interval_Max\",\"Interval_Compressed_Histogram\"");
}
/**
* Output a log format version to the log.
*/
public void outputLogFormatVersion() {
outputComment("[Histogram log format version " + HISTOGRAM_LOG_FORMAT_VERSION +"]");
}
/**
* 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.
* @param baseTimeMsec
*/
public void setBaseTime(long baseTimeMsec) {
this.baseTime = baseTimeMsec;
}
/**
* return the current base time offset (see {@link org.HdrHistogram_voltpatches.HdrHistogram.HistogramLogWriter#setBaseTime}).
* @return the current base time
*/
public long getBaseTime() {
return baseTime;
}
}