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inmem.go
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/
inmem.go
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package metrics
import (
"fmt"
"math"
"strings"
"sync"
"time"
)
// InmemSink provides a MetricSink that does in-memory aggregation
// without sending metrics over a network. It can be embedded within
// an application to provide profiling information.
type InmemSink struct {
// How long is each aggregation interval
interval time.Duration
// Retain controls how many metrics interval we keep
retain time.Duration
// maxIntervals is the maximum length of intervals.
// It is retain / interval.
maxIntervals int
// intervals is a slice of the retained intervals
intervals []*IntervalMetrics
intervalLock sync.RWMutex
}
// IntervalMetrics stores the aggregated metrics
// for a specific interval
type IntervalMetrics struct {
sync.RWMutex
// The start time of the interval
Interval time.Time
// Gauges maps the key to the last set value
Gauges map[string]float32
// Points maps the string to the list of emitted values
// from EmitKey
Points map[string][]float32
// Counters maps the string key to a sum of the counter
// values
Counters map[string]*AggregateSample
// Samples maps the key to an AggregateSample,
// which has the rolled up view of a sample
Samples map[string]*AggregateSample
}
// NewIntervalMetrics creates a new IntervalMetrics for a given interval
func NewIntervalMetrics(intv time.Time) *IntervalMetrics {
return &IntervalMetrics{
Interval: intv,
Gauges: make(map[string]float32),
Points: make(map[string][]float32),
Counters: make(map[string]*AggregateSample),
Samples: make(map[string]*AggregateSample),
}
}
// AggregateSample is used to hold aggregate metrics
// about a sample
type AggregateSample struct {
Count int // The count of emitted pairs
Sum float64 // The sum of values
SumSq float64 // The sum of squared values
Min float64 // Minimum value
Max float64 // Maximum value
LastUpdated time.Time // When value was last updated
}
// Computes a Stddev of the values
func (a *AggregateSample) Stddev() float64 {
num := (float64(a.Count) * a.SumSq) - math.Pow(a.Sum, 2)
div := float64(a.Count * (a.Count - 1))
if div == 0 {
return 0
}
return math.Sqrt(num / div)
}
// Computes a mean of the values
func (a *AggregateSample) Mean() float64 {
if a.Count == 0 {
return 0
}
return a.Sum / float64(a.Count)
}
// Ingest is used to update a sample
func (a *AggregateSample) Ingest(v float64) {
a.Count++
a.Sum += v
a.SumSq += (v * v)
if v < a.Min || a.Count == 1 {
a.Min = v
}
if v > a.Max || a.Count == 1 {
a.Max = v
}
a.LastUpdated = time.Now()
}
func (a *AggregateSample) String() string {
if a.Count == 0 {
return "Count: 0"
} else if a.Stddev() == 0 {
return fmt.Sprintf("Count: %d Sum: %0.3f LastUpdated: %s", a.Count, a.Sum, a.LastUpdated)
} else {
return fmt.Sprintf("Count: %d Min: %0.3f Mean: %0.3f Max: %0.3f Stddev: %0.3f Sum: %0.3f LastUpdated: %s",
a.Count, a.Min, a.Mean(), a.Max, a.Stddev(), a.Sum, a.LastUpdated)
}
}
// NewInmemSink is used to construct a new in-memory sink.
// Uses an aggregation interval and maximum retention period.
func NewInmemSink(interval, retain time.Duration) *InmemSink {
i := &InmemSink{
interval: interval,
retain: retain,
maxIntervals: int(retain / interval),
}
i.intervals = make([]*IntervalMetrics, 0, i.maxIntervals)
return i
}
func (i *InmemSink) SetGauge(key []string, val float32) {
k := i.flattenKey(key)
intv := i.getInterval()
intv.Lock()
defer intv.Unlock()
intv.Gauges[k] = val
}
func (i *InmemSink) EmitKey(key []string, val float32) {
k := i.flattenKey(key)
intv := i.getInterval()
intv.Lock()
defer intv.Unlock()
vals := intv.Points[k]
intv.Points[k] = append(vals, val)
}
func (i *InmemSink) IncrCounter(key []string, val float32) {
k := i.flattenKey(key)
intv := i.getInterval()
intv.Lock()
defer intv.Unlock()
agg := intv.Counters[k]
if agg == nil {
agg = &AggregateSample{}
intv.Counters[k] = agg
}
agg.Ingest(float64(val))
}
func (i *InmemSink) AddSample(key []string, val float32) {
k := i.flattenKey(key)
intv := i.getInterval()
intv.Lock()
defer intv.Unlock()
agg := intv.Samples[k]
if agg == nil {
agg = &AggregateSample{}
intv.Samples[k] = agg
}
agg.Ingest(float64(val))
}
// Data is used to retrieve all the aggregated metrics
// Intervals may be in use, and a read lock should be acquired
func (i *InmemSink) Data() []*IntervalMetrics {
// Get the current interval, forces creation
i.getInterval()
i.intervalLock.RLock()
defer i.intervalLock.RUnlock()
intervals := make([]*IntervalMetrics, len(i.intervals))
copy(intervals, i.intervals)
return intervals
}
func (i *InmemSink) getExistingInterval(intv time.Time) *IntervalMetrics {
i.intervalLock.RLock()
defer i.intervalLock.RUnlock()
n := len(i.intervals)
if n > 0 && i.intervals[n-1].Interval == intv {
return i.intervals[n-1]
}
return nil
}
func (i *InmemSink) createInterval(intv time.Time) *IntervalMetrics {
i.intervalLock.Lock()
defer i.intervalLock.Unlock()
// Check for an existing interval
n := len(i.intervals)
if n > 0 && i.intervals[n-1].Interval == intv {
return i.intervals[n-1]
}
// Add the current interval
current := NewIntervalMetrics(intv)
i.intervals = append(i.intervals, current)
n++
// Truncate the intervals if they are too long
if n >= i.maxIntervals {
copy(i.intervals[0:], i.intervals[n-i.maxIntervals:])
i.intervals = i.intervals[:i.maxIntervals]
}
return current
}
// getInterval returns the current interval to write to
func (i *InmemSink) getInterval() *IntervalMetrics {
intv := time.Now().Truncate(i.interval)
if m := i.getExistingInterval(intv); m != nil {
return m
}
return i.createInterval(intv)
}
// Flattens the key for formatting, removes spaces
func (i *InmemSink) flattenKey(parts []string) string {
joined := strings.Join(parts, ".")
return strings.Replace(joined, " ", "_", -1)
}