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vendor/cloud.google.com/go/bigtable/internal/stat/stats.go

@@ -0,0 +1,144 @@
+// Copyright 2016 Google Inc. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package stat
+
+import (
+	"bytes"
+	"encoding/csv"
+	"fmt"
+	"io"
+	"math"
+	"sort"
+	"strconv"
+	"text/tabwriter"
+	"time"
+)
+
+type byDuration []time.Duration
+
+func (data byDuration) Len() int           { return len(data) }
+func (data byDuration) Swap(i, j int)      { data[i], data[j] = data[j], data[i] }
+func (data byDuration) Less(i, j int) bool { return data[i] < data[j] }
+
+// quantile returns a value representing the kth of q quantiles.
+// May alter the order of data.
+func quantile(data []time.Duration, k, q int) (quantile time.Duration, ok bool) {
+	if len(data) < 1 {
+		return 0, false
+	}
+	if k > q {
+		return 0, false
+	}
+	if k < 0 || q < 1 {
+		return 0, false
+	}
+
+	sort.Sort(byDuration(data))
+
+	if k == 0 {
+		return data[0], true
+	}
+	if k == q {
+		return data[len(data)-1], true
+	}
+
+	bucketSize := float64(len(data)-1) / float64(q)
+	i := float64(k) * bucketSize
+
+	lower := int(math.Trunc(i))
+	var upper int
+	if i > float64(lower) && lower+1 < len(data) {
+		// If the quantile lies between two elements
+		upper = lower + 1
+	} else {
+		upper = lower
+	}
+	weightUpper := i - float64(lower)
+	weightLower := 1 - weightUpper
+	return time.Duration(weightLower*float64(data[lower]) + weightUpper*float64(data[upper])), true
+}
+
+type Aggregate struct {
+	Name               string
+	Count, Errors      int
+	Min, Median, Max   time.Duration
+	P75, P90, P95, P99 time.Duration // percentiles
+}
+
+// NewAggregate constructs an aggregate from latencies. Returns nil if latencies does not contain aggregateable data.
+func NewAggregate(name string, latencies []time.Duration, errorCount int) *Aggregate {
+	agg := Aggregate{Name: name, Count: len(latencies), Errors: errorCount}
+
+	if len(latencies) == 0 {
+		return nil
+	}
+	var ok bool
+	if agg.Min, ok = quantile(latencies, 0, 2); !ok {
+		return nil
+	}
+	if agg.Median, ok = quantile(latencies, 1, 2); !ok {
+		return nil
+	}
+	if agg.Max, ok = quantile(latencies, 2, 2); !ok {
+		return nil
+	}
+	if agg.P75, ok = quantile(latencies, 75, 100); !ok {
+		return nil
+	}
+	if agg.P90, ok = quantile(latencies, 90, 100); !ok {
+		return nil
+	}
+	if agg.P95, ok = quantile(latencies, 95, 100); !ok {
+		return nil
+	}
+	if agg.P99, ok = quantile(latencies, 99, 100); !ok {
+		return nil
+	}
+	return &agg
+}
+
+func (agg *Aggregate) String() string {
+	if agg == nil {
+		return "no data"
+	}
+	var buf bytes.Buffer
+	tw := tabwriter.NewWriter(&buf, 0, 0, 1, ' ', 0) // one-space padding
+	fmt.Fprintf(tw, "min:\t%v\nmedian:\t%v\nmax:\t%v\n95th percentile:\t%v\n99th percentile:\t%v\n",
+		agg.Min, agg.Median, agg.Max, agg.P95, agg.P99)
+	tw.Flush()
+	return buf.String()
+}
+
+// WriteCSV writes a csv file to the given Writer,
+// with a header row and one row per aggregate.
+func WriteCSV(aggs []*Aggregate, iow io.Writer) error {
+	w := csv.NewWriter(iow)
+	defer w.Flush()
+	err := w.Write([]string{"name", "count", "errors", "min", "median", "max", "p75", "p90", "p95", "p99"})
+	if err != nil {
+		return err
+	}
+	for _, agg := range aggs {
+		err = w.Write([]string{
+			agg.Name, strconv.Itoa(agg.Count), strconv.Itoa(agg.Errors),
+			agg.Min.String(), agg.Median.String(), agg.Max.String(),
+			agg.P75.String(), agg.P90.String(), agg.P95.String(), agg.P99.String(),
+		})
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}