1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
|
// Copyright The OpenTelemetry Authors
// SPDX-License-Identifier: Apache-2.0
package exemplar // import "go.opentelemetry.io/otel/sdk/metric/exemplar"
import (
"context"
"time"
"go.opentelemetry.io/otel/attribute"
"go.opentelemetry.io/otel/trace"
)
// storage is an exemplar storage for [Reservoir] implementations.
type storage struct {
// store are the measurements sampled.
//
// This does not use []metricdata.Exemplar because it potentially would
// require an allocation for trace and span IDs in the hot path of Offer.
store []measurement
}
func newStorage(n int) *storage {
return &storage{store: make([]measurement, n)}
}
// Collect returns all the held exemplars.
//
// The Reservoir state is preserved after this call.
func (r *storage) Collect(dest *[]Exemplar) {
*dest = reset(*dest, len(r.store), len(r.store))
var n int
for _, m := range r.store {
if !m.valid {
continue
}
m.exemplar(&(*dest)[n])
n++
}
*dest = (*dest)[:n]
}
// measurement is a measurement made by a telemetry system.
type measurement struct {
// FilteredAttributes are the attributes dropped during the measurement.
FilteredAttributes []attribute.KeyValue
// Time is the time when the measurement was made.
Time time.Time
// Value is the value of the measurement.
Value Value
// SpanContext is the SpanContext active when a measurement was made.
SpanContext trace.SpanContext
valid bool
}
// newMeasurement returns a new non-empty Measurement.
func newMeasurement(ctx context.Context, ts time.Time, v Value, droppedAttr []attribute.KeyValue) measurement {
return measurement{
FilteredAttributes: droppedAttr,
Time: ts,
Value: v,
SpanContext: trace.SpanContextFromContext(ctx),
valid: true,
}
}
// exemplar returns m as an [Exemplar].
func (m measurement) exemplar(dest *Exemplar) {
dest.FilteredAttributes = m.FilteredAttributes
dest.Time = m.Time
dest.Value = m.Value
if m.SpanContext.HasTraceID() {
traceID := m.SpanContext.TraceID()
dest.TraceID = traceID[:]
} else {
dest.TraceID = dest.TraceID[:0]
}
if m.SpanContext.HasSpanID() {
spanID := m.SpanContext.SpanID()
dest.SpanID = spanID[:]
} else {
dest.SpanID = dest.SpanID[:0]
}
}
func reset[T any](s []T, length, capacity int) []T {
if cap(s) < capacity {
return make([]T, length, capacity)
}
return s[:length]
}
|
