percentile

type Entries ¶

type Entries []Entry

Entries is a slice of Entry

func (slice Entries) Len() int

func (slice Entries) Less(i, j int) bool

func (slice Entries) Swap(i, j int)

type Entry ¶

type Entry struct {
	V     float64 `json:"v"`
	G     uint32  `json:"g"`
	Delta uint32  `json:"d"`
}

Entry is an element of the sketch. For the definition of g and delta, see the original paper http://infolab.stanford.edu/~datar/courses/cs361a/papers/quantiles.pdf

func (e *Entry) MarshalJSON() ([]byte, error)

func (e *Entry) UnmarshalJSON(b []byte) error

type GKArray ¶

type GKArray struct {
	// the last item of Entries will always be the max inserted value
	Entries  Entries   `json:"entries"`
	Incoming []float64 `json:"buf"`
	// TODO[Charles]: incorporate min in entries so that we can get rid of the field.
	Min   float64 `json:"min"`
	Max   float64 `json:"max"`
	Count int64   `json:"cnt"`
	Sum   float64 `json:"sum"`
	Avg   float64 `json:"avg"`
}

GKArray is a version of GK with a buffer for the incoming values. The expected usage is that Add() is called in the agent, while Merge() and Quantile() are called in the backend; in other words, values are added to the sketch in the agent, sketches are sent to the backend where they are merged with other sketches, and quantile queries are made to the merged sketches only. This allows us to ignore the Incoming buffer once the sketch goes through a Merge. GKArray therefore has two versions of compress:

1. compressWithIncoming(incomingEntries []Entry) is used during Merge(), and sets Incoming to nil after compressing so that merged sketches do not allocate unnecessary storage.
2. compressAndAllocateBuf() is used during Add(), and allocates Incoming after compressing for further addition of values to the sketch.

func NewGKArray() GKArray

func (s GKArray) Add(v float64) GKArray

func (s GKArray) IsValid() bool

func (s GKArray) Merge(o GKArray) GKArray

func (s GKArray) Quantile(q float64) float64

func (s GKArray) Quantiles(qValues []float64) []float64

type NoSketchError ¶

type NoSketchError struct{}

NoSketchError is the error returned when not enough samples have been submitted to generate a sketch

func (e NoSketchError) Error() string

type Sketch ¶

type Sketch struct {
	Timestamp int64   `json:"timestamp"`
	Sketch    GKArray `json:"qsketch"`
}

Sketch represents a quantile sketch at a specific time

type SketchSeries ¶

type SketchSeries struct {
	Name       string          `json:"metric"`
	Tags       []string        `json:"tags"`
	Host       string          `json:"host"`
	Interval   int64           `json:"interval"`
	Sketches   []Sketch        `json:"sketches"`
	ContextKey ckey.ContextKey `json:"-"`
}

SketchSeries holds an array of sketches.

type SketchSeriesList ¶

type SketchSeriesList []*SketchSeries

SketchSeriesList represents a list of SketchSeries ready to be serialized

func (sl SketchSeriesList) Marshal() ([]byte, error)

func (sl SketchSeriesList) MarshalJSON() ([]byte, error)

func (sl SketchSeriesList) SplitPayload(times int) ([]marshaler.Marshaler, error)