Implement statistics logger

stats/logger.go

@@ -0,0 +1,106 @@
+package stats
+
+import (
+	"fmt"
+	"io"
+	"os"
+	"sync"
+	"time"
+
+	"github.com/rcrowley/go-metrics"
+)
+
+type Logger struct {
+	sync.Mutex
+	out      io.Writer
+	interval time.Duration
+	stats    map[string]*loggerStats
+}
+
+type loggerStats struct {
+	time   metrics.Histogram
+	errors metrics.Counter
+}
+
+func NewLogger(out io.Writer, interval time.Duration) *Logger {
+	l := &Logger{
+		out:      out,
+		interval: interval,
+		stats:    make(map[string]*loggerStats),
+	}
+	go l.printWithInterval()
+
+	return l
+}
+
+func NewStdoutLogger(interval time.Duration) *Logger {
+	l := &Logger{
+		out:      os.Stdout,
+		interval: interval,
+		stats:    make(map[string]*loggerStats),
+	}
+	go l.printWithInterval()
+
+	return l
+}
+
+func (l *Logger) Add(name string, dur time.Duration) {
+	l.metrics(name).time.Update(int64(dur))
+}
+
+func (l *Logger) Error(name string) {
+	l.metrics(name).errors.Inc(1)
+}
+
+func (l *Logger) Print() {
+	for name, s := range l.stats {
+		fmt.Fprintf(l.out, "%s statistics:\n"+
+			"Processed: %d\n"+
+			"Errors:    %d\n"+
+			"Min:       %.8fms\n"+
+			"Max:       %.8fms\n"+
+			"95%%:       %.8fms\n"+
+			"Mean:      %.8fms\n"+
+			"StdDev:    %.8fms\n",
+			name,
+			s.time.Count(),
+			s.errors.Count(),
+			float64(s.time.Min())/1000000,
+			float64(s.time.Max())/1000000,
+			s.time.Percentile(0.95)/1000000,
+			s.time.Mean()/1000000,
+			s.time.StdDev()/1000000,
+		)
+		s.time.Clear()
+		s.errors.Clear()
+	}
+}
+
+func (l *Logger) printWithInterval() {
+	if l.interval == 0 {
+		return
+	}
+
+	for range time.NewTicker(l.interval).C {
+		l.Print()
+	}
+}
+
+func (l *Logger) metrics(name string) *loggerStats {
+	if _, ok := l.stats[name]; !ok {
+		l.Lock()
+		defer l.Unlock()
+
+		// Double checking being protected by mutex
+		if s, ok := l.stats[name]; ok {
+			return s
+		}
+
+		l.stats[name] = &loggerStats{
+			time:   metrics.NewHistogram(metrics.NewUniformSample(1000)),
+			errors: metrics.NewCounter(),
+		}
+	}
+
+	return l.stats[name]
+}