blob: 35534dd70da50f6cf05cc21845f24e781e8dd1ad (
plain)
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
|
// Copyright 2020 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package metrics
import (
_ "runtime" // depends on the runtime via a linkname'd function
"unsafe"
)
// Sample captures a single metric sample.
type Sample struct {
// Name is the name of the metric sampled.
//
// It must correspond to a name in one of the metric descriptions
// returned by Descriptions.
Name string
// Value is the value of the metric sample.
Value Value
}
// Implemented in the runtime.
func runtime_readMetrics(unsafe.Pointer, int, int)
// Read populates each Value field in the given slice of metric samples.
//
// Desired metrics should be present in the slice with the appropriate name.
// The user of this API is encouraged to re-use the same slice between calls for
// efficiency, but is not required to do so.
//
// Note that re-use has some caveats. Notably, Values should not be read or
// manipulated while a Read with that value is outstanding; that is a data race.
// This property includes pointer-typed Values (e.g. Float64Histogram) whose
// underlying storage will be reused by Read when possible. To safely use such
// values in a concurrent setting, all data must be deep-copied.
//
// It is safe to execute multiple Read calls concurrently, but their arguments
// must share no underlying memory. When in doubt, create a new []Sample from
// scratch, which is always safe, though may be inefficient.
//
// Sample values with names not appearing in All will have their Value populated
// as KindBad to indicate that the name is unknown.
func Read(m []Sample) {
runtime_readMetrics(unsafe.Pointer(&m[0]), len(m), cap(m))
}
|
