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