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// Copyright 2018, OpenCensus Authors
//
// 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 metricdata
import (
"time"
)
// Point is a single data point of a time series.
type Point struct {
// Time is the point in time that this point represents in a time series.
Time time.Time
// Value is the value of this point. Prefer using ReadValue to switching on
// the value type, since new value types might be added.
Value interface{}
}
//go:generate stringer -type ValueType
// NewFloat64Point creates a new Point holding a float64 value.
func NewFloat64Point(t time.Time, val float64) Point {
return Point{
Value: val,
Time: t,
}
}
// NewInt64Point creates a new Point holding an int64 value.
func NewInt64Point(t time.Time, val int64) Point {
return Point{
Value: val,
Time: t,
}
}
// NewDistributionPoint creates a new Point holding a Distribution value.
func NewDistributionPoint(t time.Time, val *Distribution) Point {
return Point{
Value: val,
Time: t,
}
}
// NewSummaryPoint creates a new Point holding a Summary value.
func NewSummaryPoint(t time.Time, val *Summary) Point {
return Point{
Value: val,
Time: t,
}
}
// ValueVisitor allows reading the value of a point.
type ValueVisitor interface {
VisitFloat64Value(float64)
VisitInt64Value(int64)
VisitDistributionValue(*Distribution)
VisitSummaryValue(*Summary)
}
// ReadValue accepts a ValueVisitor and calls the appropriate method with the
// value of this point.
// Consumers of Point should use this in preference to switching on the type
// of the value directly, since new value types may be added.
func (p Point) ReadValue(vv ValueVisitor) {
switch v := p.Value.(type) {
case int64:
vv.VisitInt64Value(v)
case float64:
vv.VisitFloat64Value(v)
case *Distribution:
vv.VisitDistributionValue(v)
case *Summary:
vv.VisitSummaryValue(v)
default:
panic("unexpected value type")
}
}
// Distribution contains summary statistics for a population of values. It
// optionally contains a histogram representing the distribution of those
// values across a set of buckets.
type Distribution struct {
// Count is the number of values in the population. Must be non-negative. This value
// must equal the sum of the values in bucket_counts if a histogram is
// provided.
Count int64
// Sum is the sum of the values in the population. If count is zero then this field
// must be zero.
Sum float64
// SumOfSquaredDeviation is the sum of squared deviations from the mean of the values in the
// population. For values x_i this is:
//
// Sum[i=1..n]((x_i - mean)^2)
//
// Knuth, "The Art of Computer Programming", Vol. 2, page 323, 3rd edition
// describes Welford's method for accumulating this sum in one pass.
//
// If count is zero then this field must be zero.
SumOfSquaredDeviation float64
// BucketOptions describes the bounds of the histogram buckets in this
// distribution.
//
// A Distribution may optionally contain a histogram of the values in the
// population.
//
// If nil, there is no associated histogram.
BucketOptions *BucketOptions
// Bucket If the distribution does not have a histogram, then omit this field.
// If there is a histogram, then the sum of the values in the Bucket counts
// must equal the value in the count field of the distribution.
Buckets []Bucket
}
// BucketOptions describes the bounds of the histogram buckets in this
// distribution.
type BucketOptions struct {
// Bounds specifies a set of bucket upper bounds.
// This defines len(bounds) + 1 (= N) buckets. The boundaries for bucket
// index i are:
//
// [0, Bounds[i]) for i == 0
// [Bounds[i-1], Bounds[i]) for 0 < i < N-1
// [Bounds[i-1], +infinity) for i == N-1
Bounds []float64
}
// Bucket represents a single bucket (value range) in a distribution.
type Bucket struct {
// Count is the number of values in each bucket of the histogram, as described in
// bucket_bounds.
Count int64
// Exemplar associated with this bucket (if any).
Exemplar *Exemplar
}
// Summary is a representation of percentiles.
type Summary struct {
// Count is the cumulative count (if available).
Count int64
// Sum is the cumulative sum of values (if available).
Sum float64
// HasCountAndSum is true if Count and Sum are available.
HasCountAndSum bool
// Snapshot represents percentiles calculated over an arbitrary time window.
// The values in this struct can be reset at arbitrary unknown times, with
// the requirement that all of them are reset at the same time.
Snapshot Snapshot
}
// Snapshot represents percentiles over an arbitrary time.
// The values in this struct can be reset at arbitrary unknown times, with
// the requirement that all of them are reset at the same time.
type Snapshot struct {
// Count is the number of values in the snapshot. Optional since some systems don't
// expose this. Set to 0 if not available.
Count int64
// Sum is the sum of values in the snapshot. Optional since some systems don't
// expose this. If count is 0 then this field must be zero.
Sum float64
// Percentiles is a map from percentile (range (0-100.0]) to the value of
// the percentile.
Percentiles map[float64]float64
}
//go:generate stringer -type Type
// Type is the overall type of metric, including its value type and whether it
// represents a cumulative total (since the start time) or if it represents a
// gauge value.
type Type int
// Metric types.
const (
TypeGaugeInt64 Type = iota
TypeGaugeFloat64
TypeGaugeDistribution
TypeCumulativeInt64
TypeCumulativeFloat64
TypeCumulativeDistribution
TypeSummary
)
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