Initial commit

vendor/github.com/HdrHistogram/hdrhistogram-go/log_writer.go

@@ -0,0 +1,141 @@
+//The log format encodes into a single file, multiple histograms with optional shared meta data.
+package hdrhistogram
+
+import (
+	"fmt"
+	"io"
+	"regexp"
+	"time"
+)
+
+const HISTOGRAM_LOG_FORMAT_VERSION = "1.3"
+const MsToNsRatio float64 = 1000000.0
+
+type HistogramLogOptions struct {
+	startTimeStampSec float64
+	endTimeStampSec   float64
+	maxValueUnitRatio float64
+}
+
+func DefaultHistogramLogOptions() *HistogramLogOptions {
+	return &HistogramLogOptions{0, 0, MsToNsRatio}
+}
+
+type HistogramLogWriter struct {
+	baseTime int64
+	log      io.Writer
+}
+
+// Return the current base time offset
+func (lw *HistogramLogWriter) BaseTime() int64 {
+	return lw.baseTime
+}
+
+// Set a base time to subtract from supplied histogram start/end timestamps when
+// logging based on histogram timestamps.
+// baseTime 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.
+func (lw *HistogramLogWriter) SetBaseTime(baseTime int64) {
+	lw.baseTime = baseTime
+}
+
+func NewHistogramLogWriter(log io.Writer) *HistogramLogWriter {
+	return &HistogramLogWriter{baseTime: 0, log: log}
+}
+
+// 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
+//
+// By convention, 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 ( default ).
+// For logging with relative time stamps (time since a start point), the base time should be set with SetBaseTime(baseTime int64)
+//
+// The max value in the histogram will be reported scaled down by a default maxValueUnitRatio of 1000000.0 (which is the msec : nsec ratio).
+// If you need to specify a different start/end timestamp or a different maxValueUnitRatio you should use OutputIntervalHistogramWithLogOptions(histogram *Histogram, logOptions *HistogramLogOptions)
+func (lw *HistogramLogWriter) OutputIntervalHistogram(histogram *Histogram) (err error) {
+	return lw.OutputIntervalHistogramWithLogOptions(histogram, nil)
+}
+
+// Output an interval histogram, with the given timestamp information and the [optional] tag associated with the histogram
+//
+// If you specify non-nil logOptions, and non-zero start timestamp, the the specified timestamp information will be used, and the start timestamp information in the actual histogram will be ignored.
+// If you specify non-nil logOptions, and non-zero start timestamp, the the specified timestamp information will be used, and the end timestamp information in the actual histogram will be ignored.
+// If you specify non-nil logOptions, The max value reported with the interval line will be scaled by the given maxValueUnitRatio,
+// otherwise  a default maxValueUnitRatio of 1,000,000 (which is the msec : nsec ratio) will be used.
+//
+// By convention, 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 ( default ).
+// For logging with relative time stamps (time since a start point), the base time should be set with SetBaseTime(baseTime int64)
+func (lw *HistogramLogWriter) OutputIntervalHistogramWithLogOptions(histogram *Histogram, logOptions *HistogramLogOptions) (err error) {
+	tag := histogram.Tag()
+	var match bool
+	tagStr := ""
+	if tag != "" {
+		match, err = regexp.MatchString(".[, \\r\\n].", tag)
+		if err != nil {
+			return
+		}
+		if match {
+			err = fmt.Errorf("Tag string cannot contain commas, spaces, or line breaks. Used tag: %s", tag)
+			return
+		}
+		tagStr = fmt.Sprintf("Tag=%s,", tag)
+	}
+	var usedStartTime float64 = float64(histogram.StartTimeMs())
+	var usedEndTime float64 = float64(histogram.EndTimeMs())
+	var maxValueUnitRatio float64 = MsToNsRatio
+	if logOptions != nil {
+		if logOptions.startTimeStampSec != 0 {
+			usedStartTime = logOptions.startTimeStampSec
+		}
+		if logOptions.endTimeStampSec != 0 {
+			usedEndTime = logOptions.endTimeStampSec
+		}
+		maxValueUnitRatio = logOptions.maxValueUnitRatio
+	}
+	startTime := usedStartTime - float64(lw.baseTime)/1000.0
+	endTime := usedEndTime - float64(lw.baseTime)/1000.0
+	maxValueAsDouble := float64(histogram.Max()) / maxValueUnitRatio
+	cpayload, err := histogram.Encode(V2CompressedEncodingCookieBase)
+	if err != nil {
+		return
+	}
+	_, err = lw.log.Write([]byte(fmt.Sprintf("%s%f,%f,%f,%s\n", tagStr, startTime, endTime, maxValueAsDouble, string(cpayload))))
+	return
+}
+
+// Log a start time in the log.
+// Start time is represented as seconds since epoch with up to 3 decimal places. Line starts with the leading text '#[StartTime:'
+func (lw *HistogramLogWriter) OutputStartTime(start_time_msec int64) (err error) {
+	secs := start_time_msec / 1000
+	iso_str := time.Unix(secs, start_time_msec%int64(1000)*int64(1000000000)).Format(time.RFC3339)
+	_, err = lw.log.Write([]byte(fmt.Sprintf("#[StartTime: %d (seconds since epoch), %s]\n", secs, iso_str)))
+	return
+}
+
+// Log a base time in the log.
+// Base time is represented as seconds since epoch with up to 3 decimal places. Line starts with the leading text '#[BaseTime:'
+func (lw *HistogramLogWriter) OutputBaseTime(base_time_msec int64) (err error) {
+	secs := base_time_msec / 1000
+	_, err = lw.log.Write([]byte(fmt.Sprintf("#[Basetime: %d (seconds since epoch)]\n", secs)))
+	return
+}
+
+// Log a comment to the log.
+// A comment is any line that leads with '#' that is not matched by the BaseTime or StartTime formats. Comments are ignored when parsed.
+func (lw *HistogramLogWriter) OutputComment(comment string) (err error) {
+	_, err = lw.log.Write([]byte(fmt.Sprintf("#%s\n", comment)))
+	return
+}
+
+// Output a legend line to the log.
+// Human readable column headers. Ignored when parsed.
+func (lw *HistogramLogWriter) OutputLegend() (err error) {
+	_, err = lw.log.Write([]byte("\"StartTimestamp\",\"Interval_Length\",\"Interval_Max\",\"Interval_Compressed_Histogram\"\n"))
+	return
+}
+
+// Output a log format version to the log.
+func (lw *HistogramLogWriter) OutputLogFormatVersion() (err error) {
+	return lw.OutputComment(fmt.Sprintf("[Histogram log format version %s]", HISTOGRAM_LOG_FORMAT_VERSION))
+}