Documentation
¶
Overview ¶
Package metrics provides a stable interface to access implementation-defined metrics exported by the Go runtime. This package is similar to existing functions like runtime.ReadMemStats and [debug.ReadGCStats], but significantly more general.
The set of metrics defined by this package may evolve as the runtime itself evolves, and also enables variation across Go implementations, whose relevant metric sets may not intersect.
Interface ¶
Metrics are designated by a string key, rather than, for example, a field name in a struct. The full list of supported metrics is always available in the slice of Descriptions returned by All. Each Description also includes useful information about the metric.
Thus, users of this API are encouraged to sample supported metrics defined by the slice returned by All to remain compatible across Go versions. Of course, situations arise where reading specific metrics is critical. For these cases, users are encouraged to use build tags, and although metrics may be deprecated and removed, users should consider this to be an exceptional and rare event, coinciding with a very large change in a particular Go implementation.
Each metric key also has a "kind" that describes the format of the metric's value. In the interest of not breaking users of this package, the "kind" for a given metric is guaranteed not to change. If it must change, then a new metric will be introduced with a new key and a new "kind."
Metric key format ¶
As mentioned earlier, metric keys are strings. Their format is simple and well-defined, designed to be both human and machine readable. It is split into two components, separated by a colon: a rooted path and a unit. The choice to include the unit in the key is motivated by compatibility: if a metric's unit changes, its semantics likely did also, and a new key should be introduced.
For more details on the precise definition of the metric key's path and unit formats, see the documentation of the Name field of the Description struct.
A note about floats ¶
This package supports metrics whose values have a floating-point representation. In order to improve ease-of-use, this package promises to never produce the following classes of floating-point values: NaN, infinity.
Supported metrics ¶
Below is the full list of supported metrics, ordered lexicographically.
/cgo/go-to-c-calls:calls Count of calls made from Go to C by the current process. /cpu/classes/gc/mark/assist:cpu-seconds Estimated total CPU time goroutines spent performing GC tasks to assist the GC and prevent it from falling behind the application. This metric is an overestimate, and not directly comparable to system CPU time measurements. Compare only with other /cpu/classes metrics. /cpu/classes/gc/mark/dedicated:cpu-seconds Estimated total CPU time spent performing GC tasks on processors (as defined by GOMAXPROCS) dedicated to those tasks. This metric is an overestimate, and not directly comparable to system CPU time measurements. Compare only with other /cpu/classes metrics. /cpu/classes/gc/mark/idle:cpu-seconds Estimated total CPU time spent performing GC tasks on spare CPU resources that the Go scheduler could not otherwise find a use for. This should be subtracted from the total GC CPU time to obtain a measure of compulsory GC CPU time. This metric is an overestimate, and not directly comparable to system CPU time measurements. Compare only with other /cpu/classes metrics. /cpu/classes/gc/pause:cpu-seconds Estimated total CPU time spent with the application paused by the GC. Even if only one thread is running during the pause, this is computed as GOMAXPROCS times the pause latency because nothing else can be executing. This is the exact sum of samples in /gc/pause:seconds if each sample is multiplied by GOMAXPROCS at the time it is taken. This metric is an overestimate, and not directly comparable to system CPU time measurements. Compare only with other /cpu/classes metrics. /cpu/classes/gc/total:cpu-seconds Estimated total CPU time spent performing GC tasks. This metric is an overestimate, and not directly comparable to system CPU time measurements. Compare only with other /cpu/classes metrics. Sum of all metrics in /cpu/classes/gc. /cpu/classes/idle:cpu-seconds Estimated total available CPU time not spent executing any Go or Go runtime code. In other words, the part of /cpu/classes/total:cpu-seconds that was unused. This metric is an overestimate, and not directly comparable to system CPU time measurements. Compare only with other /cpu/classes metrics. /cpu/classes/scavenge/assist:cpu-seconds Estimated total CPU time spent returning unused memory to the underlying platform in response eagerly in response to memory pressure. This metric is an overestimate, and not directly comparable to system CPU time measurements. Compare only with other /cpu/classes metrics. /cpu/classes/scavenge/background:cpu-seconds Estimated total CPU time spent performing background tasks to return unused memory to the underlying platform. This metric is an overestimate, and not directly comparable to system CPU time measurements. Compare only with other /cpu/classes metrics. /cpu/classes/scavenge/total:cpu-seconds Estimated total CPU time spent performing tasks that return unused memory to the underlying platform. This metric is an overestimate, and not directly comparable to system CPU time measurements. Compare only with other /cpu/classes metrics. Sum of all metrics in /cpu/classes/scavenge. /cpu/classes/total:cpu-seconds Estimated total available CPU time for user Go code or the Go runtime, as defined by GOMAXPROCS. In other words, GOMAXPROCS integrated over the wall-clock duration this process has been executing for. This metric is an overestimate, and not directly comparable to system CPU time measurements. Compare only with other /cpu/classes metrics. Sum of all metrics in /cpu/classes. /cpu/classes/user:cpu-seconds Estimated total CPU time spent running user Go code. This may also include some small amount of time spent in the Go runtime. This metric is an overestimate, and not directly comparable to system CPU time measurements. Compare only with other /cpu/classes metrics. /gc/cycles/automatic:gc-cycles Count of completed GC cycles generated by the Go runtime. /gc/cycles/forced:gc-cycles Count of completed GC cycles forced by the application. /gc/cycles/total:gc-cycles Count of all completed GC cycles. /gc/gogc:percent Heap size target percentage configured by the user, otherwise 100. This value is set by the GOGC environment variable, and the runtime/debug.SetGCPercent function. /gc/gomemlimit:bytes Go runtime memory limit configured by the user, otherwise math.MaxInt64. This value is set by the GOMEMLIMIT environment variable, and the runtime/debug.SetMemoryLimit function. /gc/heap/allocs-by-size:bytes Distribution of heap allocations by approximate size. Bucket counts increase monotonically. Note that this does not include tiny objects as defined by /gc/heap/tiny/allocs:objects, only tiny blocks. /gc/heap/allocs:bytes Cumulative sum of memory allocated to the heap by the application. /gc/heap/allocs:objects Cumulative count of heap allocations triggered by the application. Note that this does not include tiny objects as defined by /gc/heap/tiny/allocs:objects, only tiny blocks. /gc/heap/frees-by-size:bytes Distribution of freed heap allocations by approximate size. Bucket counts increase monotonically. Note that this does not include tiny objects as defined by /gc/heap/tiny/allocs:objects, only tiny blocks. /gc/heap/frees:bytes Cumulative sum of heap memory freed by the garbage collector. /gc/heap/frees:objects Cumulative count of heap allocations whose storage was freed by the garbage collector. Note that this does not include tiny objects as defined by /gc/heap/tiny/allocs:objects, only tiny blocks. /gc/heap/goal:bytes Heap size target for the end of the GC cycle. /gc/heap/live:bytes Heap memory occupied by live objects that were marked by the previous GC. /gc/heap/objects:objects Number of objects, live or unswept, occupying heap memory. /gc/heap/tiny/allocs:objects Count of small allocations that are packed together into blocks. These allocations are counted separately from other allocations because each individual allocation is not tracked by the runtime, only their block. Each block is already accounted for in allocs-by-size and frees-by-size. /gc/limiter/last-enabled:gc-cycle GC cycle the last time the GC CPU limiter was enabled. This metric is useful for diagnosing the root cause of an out-of-memory error, because the limiter trades memory for CPU time when the GC's CPU time gets too high. This is most likely to occur with use of SetMemoryLimit. The first GC cycle is cycle 1, so a value of 0 indicates that it was never enabled. /gc/pauses:seconds Distribution of individual GC-related stop-the-world pause latencies. Bucket counts increase monotonically. /gc/scan/globals:bytes The total amount of global variable space that is scannable. /gc/scan/heap:bytes The total amount of heap space that is scannable. /gc/scan/stack:bytes The number of bytes of stack that were scanned last GC cycle. /gc/scan/total:bytes The total amount space that is scannable. Sum of all metrics in /gc/scan. /gc/stack/starting-size:bytes The stack size of new goroutines. /godebug/non-default-behavior/execerrdot:events The number of non-default behaviors executed by the os/exec package due to a non-default GODEBUG=execerrdot=... setting. /godebug/non-default-behavior/gocachehash:events The number of non-default behaviors executed by the cmd/go package due to a non-default GODEBUG=gocachehash=... setting. /godebug/non-default-behavior/gocachetest:events The number of non-default behaviors executed by the cmd/go package due to a non-default GODEBUG=gocachetest=... setting. /godebug/non-default-behavior/gocacheverify:events The number of non-default behaviors executed by the cmd/go package due to a non-default GODEBUG=gocacheverify=... setting. /godebug/non-default-behavior/http2client:events The number of non-default behaviors executed by the net/http package due to a non-default GODEBUG=http2client=... setting. /godebug/non-default-behavior/http2server:events The number of non-default behaviors executed by the net/http package due to a non-default GODEBUG=http2server=... setting. /godebug/non-default-behavior/installgoroot:events The number of non-default behaviors executed by the go/build package due to a non-default GODEBUG=installgoroot=... setting. /godebug/non-default-behavior/jstmpllitinterp:events The number of non-default behaviors executed by the html/template package due to a non-default GODEBUG=jstmpllitinterp=... setting. /godebug/non-default-behavior/multipartmaxheaders:events The number of non-default behaviors executed by the mime/multipart package due to a non-default GODEBUG=multipartmaxheaders=... setting. /godebug/non-default-behavior/multipartmaxparts:events The number of non-default behaviors executed by the mime/multipart package due to a non-default GODEBUG=multipartmaxparts=... setting. /godebug/non-default-behavior/multipathtcp:events The number of non-default behaviors executed by the net package due to a non-default GODEBUG=multipathtcp=... setting. /godebug/non-default-behavior/panicnil:events The number of non-default behaviors executed by the runtime package due to a non-default GODEBUG=panicnil=... setting. /godebug/non-default-behavior/randautoseed:events The number of non-default behaviors executed by the math/rand package due to a non-default GODEBUG=randautoseed=... setting. /godebug/non-default-behavior/tarinsecurepath:events The number of non-default behaviors executed by the archive/tar package due to a non-default GODEBUG=tarinsecurepath=... setting. /godebug/non-default-behavior/tlsmaxrsasize:events The number of non-default behaviors executed by the crypto/tls package due to a non-default GODEBUG=tlsmaxrsasize=... setting. /godebug/non-default-behavior/x509sha1:events The number of non-default behaviors executed by the crypto/x509 package due to a non-default GODEBUG=x509sha1=... setting. /godebug/non-default-behavior/x509usefallbackroots:events The number of non-default behaviors executed by the crypto/x509 package due to a non-default GODEBUG=x509usefallbackroots=... setting. /godebug/non-default-behavior/zipinsecurepath:events The number of non-default behaviors executed by the archive/zip package due to a non-default GODEBUG=zipinsecurepath=... setting. /memory/classes/heap/free:bytes Memory that is completely free and eligible to be returned to the underlying system, but has not been. This metric is the runtime's estimate of free address space that is backed by physical memory. /memory/classes/heap/objects:bytes Memory occupied by live objects and dead objects that have not yet been marked free by the garbage collector. /memory/classes/heap/released:bytes Memory that is completely free and has been returned to the underlying system. This metric is the runtime's estimate of free address space that is still mapped into the process, but is not backed by physical memory. /memory/classes/heap/stacks:bytes Memory allocated from the heap that is reserved for stack space, whether or not it is currently in-use. Currently, this represents all stack memory for goroutines. It also includes all OS thread stacks in non-cgo programs. Note that stacks may be allocated differently in the future, and this may change. /memory/classes/heap/unused:bytes Memory that is reserved for heap objects but is not currently used to hold heap objects. /memory/classes/metadata/mcache/free:bytes Memory that is reserved for runtime mcache structures, but not in-use. /memory/classes/metadata/mcache/inuse:bytes Memory that is occupied by runtime mcache structures that are currently being used. /memory/classes/metadata/mspan/free:bytes Memory that is reserved for runtime mspan structures, but not in-use. /memory/classes/metadata/mspan/inuse:bytes Memory that is occupied by runtime mspan structures that are currently being used. /memory/classes/metadata/other:bytes Memory that is reserved for or used to hold runtime metadata. /memory/classes/os-stacks:bytes Stack memory allocated by the underlying operating system. In non-cgo programs this metric is currently zero. This may change in the future.In cgo programs this metric includes OS thread stacks allocated directly from the OS. Currently, this only accounts for one stack in c-shared and c-archive build modes, and other sources of stacks from the OS are not measured. This too may change in the future. /memory/classes/other:bytes Memory used by execution trace buffers, structures for debugging the runtime, finalizer and profiler specials, and more. /memory/classes/profiling/buckets:bytes Memory that is used by the stack trace hash map used for profiling. /memory/classes/total:bytes All memory mapped by the Go runtime into the current process as read-write. Note that this does not include memory mapped by code called via cgo or via the syscall package. Sum of all metrics in /memory/classes. /sched/gomaxprocs:threads The current runtime.GOMAXPROCS setting, or the number of operating system threads that can execute user-level Go code simultaneously. /sched/goroutines:goroutines Count of live goroutines. /sched/latencies:seconds Distribution of the time goroutines have spent in the scheduler in a runnable state before actually running. Bucket counts increase monotonically. /sync/mutex/wait/total:seconds Approximate cumulative time goroutines have spent blocked on a sync.Mutex or sync.RWMutex. This metric is useful for identifying global changes in lock contention. Collect a mutex or block profile using the runtime/pprof package for more detailed contention data.
Index ¶
Examples ¶
Constants ¶
This section is empty.
Variables ¶
This section is empty.
Functions ¶
func Read ¶
func Read(m []Sample)
Readは与えられたメトリックサンプルのスライスの各Valueフィールドを埋めます。 望ましいメトリックは、適切な名前でスライスに存在している必要があります。 このAPIのユーザーは、効率化のために同じスライスを呼び出しの間で再利用することを推奨されますが、必須ではありません。 再利用にはいくつかの注意点があります。特に、Valueが優れている間にその値を読み取ったり操作したりしてはいけません。それはデータ競合です。 この特性は、Pointer型のValue（たとえば、Float64Histogramなど）にも含まれます。その基礎となるストレージは、可能な限りReadによって再利用されます。 このような値を並行設定で安全に使用するには、すべてのデータをディープコピーする必要があります。 複数のRead呼び出しを同時に実行することは安全ですが、その引数は共有するアンダーライイングメモリを持っていてはいけません。 疑わしい場合は、常に安全な新しい[]Sampleを作成してください。ただし、効率は悪いかもしれません。 Allに表示されない名前のサンプル値は、その名前が不明であることを示すためにKindBadとしてValueが埋められます。
Example (ReadingAllMetrics) ¶
// すべてのサポートされているメトリクスの説明を取得する。
descs := metrics.All()
// 各メトリックのサンプルを作成します。
samples := make([]metrics.Sample, len(descs))
for i := range samples {
samples[i].Name = descs[i].Name
}
// メトリクスをサンプリングします。可能な場合、サンプルスライスを再利用してください！
metrics.Read(samples)
// すべての結果を繰り返す。
for _, sample := range samples {
// 名前と値を取り出す。
name, value := sample.Name, sample.Value
// 各サンプルを処理する。
switch value.Kind() {
case metrics.KindUint64:
fmt.Printf("%s: %d\n", name, value.Uint64())
case metrics.KindFloat64:
fmt.Printf("%s: %f\n", name, value.Float64())
case metrics.KindFloat64Histogram:
// ヒストグラムはかなり大きくなるかもしれませんので、この例のために
// 中央値のざっくりした推定値を取り出しましょう。
fmt.Printf("%s: %f\n", name, medianBucket(value.Float64Histogram()))
case metrics.KindBad:
// これは起きてはいけないはずです。なぜなら、すべてのメトリクスは構築されているからです。
panic("bug in runtime/metrics package!")
default:
// 新しいメトリクスが追加されると、これが発生する可能性があります。
//
// ここでは、安全策として、単にそれをログに記録しておくことで、
// 現時点では無視します。
// 最悪の場合、一時的に新しいメトリクスの情報を見逃すかもしれませんが、
fmt.Printf("%s: unexpected metric Kind: %v\n", name, value.Kind())
}
}
Output:
Example (ReadingOneMetric) ¶
package main
import (
"github.com/shogo82148/std/fmt"
"github.com/shogo82148/std/runtime/metrics"
)
func main() {
// 読み取りたいメトリックの名前。
const myMetric = "/memory/classes/heap/free:bytes"
// メトリクスのサンプルを作成します。
sample := make([]metrics.Sample, 1)
sample[0].Name = myMetric
// メトリックをサンプリングする。
metrics.Read(sample)
// メトリックが実際にサポートされているか確認します。
// もしサポートされていなければ、結果の値は常にKindBadになります。
if sample[0].Value.Kind() == metrics.KindBad {
panic(fmt.Sprintf("metric %q no longer supported", myMetric))
}
// 結果を処理する。
//
// メトリックに特定の Kind を想定することは問題ありません。
// それらは変更されないことが保証されています。
freeBytes := sample[0].Value.Uint64()
fmt.Printf("free but not released memory: %d\n", freeBytes)
}
Output:
Types ¶
type Description ¶
type Description struct {
// Nameは単位を含むメトリクスのフルネームです。
//
// メトリクスの形式は以下の正規表現で表されます。
//
// ^(?P<name>/[^:]+):(?P<unit>[^:*/]+(?:[*/][^:*/]+)*)$
//
// この形式は、名前をコロンで区切られた2つのコンポーネントに分割します。1つは常に/で始まるパスであり、もう1つは機械で解釈可能な単位です。名前は/文字の間に任意の有効なUnicodeコードポイントを含むことができますが、慣例として小文字の英字とハイフンを使用することが推奨されています。このようなパスの例としては、"/memory/heap/free"があります。
//
// 単位は、*または/で区切られた接頭辞のない小文字の英語の単位名（単数形または複数形）の連続です。単位名には、区切り文字でない有効なUnicodeコードポイントを含めることができます。単位の例には、"seconds"、"bytes"、"bytes/second"、"cpu-seconds"、"byte*cpu-seconds"、および"bytes/second/second"があります。
//
// ヒストグラムの場合、複数の単位が適用される場合があります。たとえば、バケットの単位とカウントの単位です。ヒストグラムの場合、カウントの単位は常に"samples"であり、サンプルのタイプはメトリクスの名前で明示されますが、名前の単位はバケットの単位を指定します。
//
// 完全な名前の例としては、"/memory/heap/free:bytes"があります。
Name string
// Descriptionはメトリックを説明する英文です。
Description string
// Kindはこのメトリックの値の種類です。
//
// このフィールドの目的は、アプリケーションが理解できない型の値を持つメトリックをフィルタリングできるようにすることです。
Kind ValueKind
// Cumulativeはメトリクスが累積的かどうかを示します。累積メトリクスが単一の数値である場合、それは単調に増加します。メトリクスが分布である場合、各バケットのカウントが単調に増加します。
//
// したがって、このフラグはこの値からレートを計算することが有用かどうかを示します。
Cumulative bool
}
Descriptionはランタイムメトリクスを説明します。
type Float64Histogram ¶
type Float64Histogram struct {
// Countsには、各ヒストグラムバケットの重みが格納されています。
//
// バケット数Nが与えられた場合、Count[n]は範囲[bucket[n]、bucket[n+1])の重みです。
// ただし、0 <= n < N。
Counts []uint64
// Buckets はヒストグラムのバケットの境界を含み、増加する順序で格納します。
//
// Buckets[0] は最小バケットの包括的な下限であり、
// Buckets[len(Buckets)-1] は最大バケットの排他的な上限です。
// したがって、len(Buckets)-1 個のカウントがあります。さらに、len(Buckets) != 1 は常に成り立ちます。
// なぜならば、少なくとも 2 つの境界が必要で、0 個の境界を使用して 0 個のバケットを記述するためです。
//
// Buckets[0] には値 -Inf を許可し、Buckets[len(Buckets)-1] には値 Inf を許可します。
//
// 特定のメトリック名に対して、Buckets の値はプログラムの終了まで呼び出しの間変わらないことが保証されています。
//
// このスライスの値は、他の Float64Histograms の Buckets フィールドとエイリアスを持つことが許可されているため、
// 内部の値は読み取ることしかできません。変更する必要がある場合は、ユーザーがコピーを作成する必要があります。
Buckets []float64
}
Float64Histogramはfloat64値の分布を表します。
type Sample ¶
type Sample struct {
// Nameはサンプリングされたメトリクスの名前です。
//
// これは、Allによって返されるメトリクスの説明の1つの名前と対応する必要があります。
Name string
// Valueはメトリックサンプルの値です。
Value Value
}
サンプルは単一のメトリックサンプルをキャプチャします。
type Value ¶
type Value struct {
// contains filtered or unexported fields
}
Valueはランタイムが返すメトリック値を表します。
func (Value) Float64 ¶
Float64はメトリックの内部float64値を返します。
もしv.Kind() != KindFloat64なら、このメソッドはパニックを引き起こします。
func (Value) Float64Histogram ¶
func (v Value) Float64Histogram() *Float64Histogram
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