// 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 All. 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 (for example, 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)) }