介绍与应用
expvar 是 exposed variable 的简写
expvar 包是 Golang 官网为裸露 Go 利用外部指标数据所提供的规范对外接口，能够辅助获取和调试全局变量。
其通过 init 函数将内置的 expvarHandler(一个规范 http HandlerFunc)注册到 http 包 ListenAndServe 创立的默认 Server 上
如以下案例:
package main
import (
"encoding/json"
"expvar"
"fmt"
"github.com/gin-gonic/gin"
"net/http"
"runtime"
"time"
)
func main() {router := gin.Default() // 初始化一个 gin 实例
router.GET("/debug/vars", GetCurrentRunningStats) // 接口路由，如果 url 不是 /debug/vars，则用 metricBeat 去获取会出问题
s := &http.Server{
Addr: ":" + "6666",
Handler: router,
ReadTimeout: 5 * time.Second,
WriteTimeout: 5 * time.Second,
MaxHeaderBytes: 1 << 20,
}
s.ListenAndServe() // 开始监听}
var CuMemoryPtr *map[string]string
var BTCMemoryPtr *map[string]interface{}
// 开始工夫
var start = time.Now()
// calculateUptime 计算运行工夫
func calculateUptime() interface{} {return time.Since(start).String()}
// currentGoVersion 以后 Golang 版本
func currentGoVersion() interface{} {return runtime.Version()
}
// getNumCPUs 获取 CPU 外围数量
func getNumCPUs() interface{} {return runtime.NumCPU()
}
// getGoOS 以后零碎类型
func getGoOS() interface{} {return runtime.GOOS}
// getNumGoroutins 以后 goroutine 数量
func getNumGoroutins() interface{} {return runtime.NumGoroutine()
}
// getNumCgoCall CGo 调用次数
func getNumCgoCall() interface{} {return runtime.NumCgoCall()
}
// 业务特定的内存数据
func getCuMemoryMap() interface{} {
if CuMemoryPtr == nil {return 0} else {return len(*CuMemoryPtr)
}
}
// 业务特定的内存数据
func getBTCMemoryMap() interface{} {
if BTCMemoryPtr == nil {return 0} else {return len(*BTCMemoryPtr)
}
}
var lastPause uint32
// getLastGCPauseTime 获取上次 GC 的暂停工夫
func getLastGCPauseTime() interface{} {
var gcPause uint64
ms := new(runtime.MemStats)
statString := expvar.Get("memstats").String()
if statString != "" {json.Unmarshal([]byte(statString), ms)
if lastPause == 0 || lastPause != ms.NumGC {gcPause = ms.PauseNs[(ms.NumGC+255)%256]
lastPause = ms.NumGC
}
}
return gcPause
}
// GetCurrentRunningStats 返回以后运行信息
func GetCurrentRunningStats(c *gin.Context) {c.Writer.Header().Set("Content-Type", "application/json; charset=utf-8")
first := true
report := func(key string, value interface{}) {
if !first {fmt.Fprintf(c.Writer, ",\n")
}
first = false
if str, ok := value.(string); ok {fmt.Fprintf(c.Writer, "%q: %q", key, str)
} else {fmt.Fprintf(c.Writer, "%q: %v", key, value)
}
}
fmt.Fprintf(c.Writer, "{\n")
expvar.Do(func(kv expvar.KeyValue) {report(kv.Key, kv.Value)
})
fmt.Fprintf(c.Writer, "\n}\n")
c.String(http.StatusOK, "")
}
func init() { // 这些都是自定义变量，公布到 expvar 中，每次申请接口，expvar 会主动去获取这些变量，并返回
expvar.Publish("运行工夫", expvar.Func(calculateUptime))
expvar.Publish("version", expvar.Func(currentGoVersion))
expvar.Publish("cores", expvar.Func(getNumCPUs))
expvar.Publish("os", expvar.Func(getGoOS))
expvar.Publish("cgo", expvar.Func(getNumCgoCall))
expvar.Publish("goroutine", expvar.Func(getNumGoroutins))
expvar.Publish("gcpause", expvar.Func(getLastGCPauseTime))
expvar.Publish("CuMemory", expvar.Func(getCuMemoryMap))
expvar.Publish("BTCMemory", expvar.Func(getBTCMemoryMap))
}
运行程序，并申请127.0.0.1:6666/debug/vars
<details>
<summary>后果如下：</summary>
{
"BTCMemory": 0,
"CuMemory": 0,
"cgo": 1,
"cmdline": ["/var/folders/9t/839s3jmj73bcgyp5x_xh3gw00000gn/T/go-build1753052226/b001/exe/1"],
"cores": 8,
"gcpause": 0,
"goroutine": 3,
"memstats": {
"Alloc": 1516104,
"TotalAlloc": 1516104,
"Sys": 71961616,
"Lookups": 0,
"Mallocs": 12075,
"Frees": 1237,
"HeapAlloc": 1516104,
"HeapSys": 66650112,
"HeapIdle": 63930368,
"HeapInuse": 2719744,
"HeapReleased": 63930368,
"HeapObjects": 10838,
"StackInuse": 458752,
"StackSys": 458752,
"MSpanInuse": 46376,
"MSpanSys": 49152,
"MCacheInuse": 9600,
"MCacheSys": 16384,
"BuckHashSys": 4156,
"GCSys": 4227128,
"OtherSys": 555932,
"NextGC": 4473924,
"LastGC": 0,
"PauseTotalNs": 0,
"PauseNs": [
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"PauseEnd": [
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],
"NumGC": 0,
"NumForcedGC": 0,
"GCCPUFraction": 0,
"EnableGC": true,
"DebugGC": false,
"BySize": [
{
"Size": 0,
"Mallocs": 0,
"Frees": 0
},
{
"Size": 8,
"Mallocs": 251,
"Frees": 0
},
{
"Size": 16,
"Mallocs": 4258,
"Frees": 0
},
{
"Size": 24,
"Mallocs": 490,
"Frees": 0
},
{
"Size": 32,
"Mallocs": 1194,
"Frees": 0
},
{
"Size": 48,
"Mallocs": 745,
"Frees": 0
},
{
"Size": 64,
"Mallocs": 572,
"Frees": 0
},
{
"Size": 80,
"Mallocs": 72,
"Frees": 0
},
{
"Size": 96,
"Mallocs": 84,
"Frees": 0
},
{
"Size": 112,
"Mallocs": 2268,
"Frees": 0
},
{
"Size": 128,
"Mallocs": 79,
"Frees": 0
},
{
"Size": 144,
"Mallocs": 19,
"Frees": 0
},
{
"Size": 160,
"Mallocs": 164,
"Frees": 0
},
{
"Size": 176,
"Mallocs": 11,
"Frees": 0
},
{
"Size": 192,
"Mallocs": 16,
"Frees": 0
},
{
"Size": 208,
"Mallocs": 73,
"Frees": 0
},
{
"Size": 224,
"Mallocs": 5,
"Frees": 0
},
{
"Size": 240,
"Mallocs": 4,
"Frees": 0
},
{
"Size": 256,
"Mallocs": 30,
"Frees": 0
},
{
"Size": 288,
"Mallocs": 28,
"Frees": 0
},
{
"Size": 320,
"Mallocs": 50,
"Frees": 0
},
{
"Size": 352,
"Mallocs": 11,
"Frees": 0
},
{
"Size": 384,
"Mallocs": 30,
"Frees": 0
},
{
"Size": 416,
"Mallocs": 25,
"Frees": 0
},
{
"Size": 448,
"Mallocs": 3,
"Frees": 0
},
{
"Size": 480,
"Mallocs": 0,
"Frees": 0
},
{
"Size": 512,
"Mallocs": 9,
"Frees": 0
},
{
"Size": 576,
"Mallocs": 18,
"Frees": 0
},
{
"Size": 640,
"Mallocs": 57,
"Frees": 0
},
{
"Size": 704,
"Mallocs": 8,
"Frees": 0
},
{
"Size": 768,
"Mallocs": 1,
"Frees": 0
},
{
"Size": 896,
"Mallocs": 19,
"Frees": 0
},
{
"Size": 1024,
"Mallocs": 26,
"Frees": 0
},
{
"Size": 1152,
"Mallocs": 23,
"Frees": 0
},
{
"Size": 1280,
"Mallocs": 36,
"Frees": 0
},
{
"Size": 1408,
"Mallocs": 1,
"Frees": 0
},
{
"Size": 1536,
"Mallocs": 3,
"Frees": 0
},
{
"Size": 1792,
"Mallocs": 22,
"Frees": 0
},
{
"Size": 2048,
"Mallocs": 7,
"Frees": 0
},
{
"Size": 2304,
"Mallocs": 3,
"Frees": 0
},
{
"Size": 2688,
"Mallocs": 38,
"Frees": 0
},
{
"Size": 3072,
"Mallocs": 6,
"Frees": 0
},
{
"Size": 3200,
"Mallocs": 2,
"Frees": 0
},
{
"Size": 3456,
"Mallocs": 3,
"Frees": 0
},
{
"Size": 4096,
"Mallocs": 20,
"Frees": 0
},
{
"Size": 4864,
"Mallocs": 2,
"Frees": 0
},
{
"Size": 5376,
"Mallocs": 15,
"Frees": 0
},
{
"Size": 6144,
"Mallocs": 6,
"Frees": 0
},
{
"Size": 6528,
"Mallocs": 1,
"Frees": 0
},
{
"Size": 6784,
"Mallocs": 2,
"Frees": 0
},
{
"Size": 6912,
"Mallocs": 0,
"Frees": 0
},
{
"Size": 8192,
"Mallocs": 3,
"Frees": 0
},
{
"Size": 9472,
"Mallocs": 2,
"Frees": 0
},
{
"Size": 9728,
"Mallocs": 3,
"Frees": 0
},
{
"Size": 10240,
"Mallocs": 8,
"Frees": 0
},
{
"Size": 10880,
"Mallocs": 8,
"Frees": 0
},
{
"Size": 12288,
"Mallocs": 0,
"Frees": 0
},
{
"Size": 13568,
"Mallocs": 0,
"Frees": 0
},
{
"Size": 14336,
"Mallocs": 0,
"Frees": 0
},
{
"Size": 16384,
"Mallocs": 0,
"Frees": 0
},
{
"Size": 18432,
"Mallocs": 1,
"Frees": 0
}
]
},
"os": "darwin",
"version": "go1.16.7",
"运行工夫": "30.037286084s"
}</details>
其中，expvar 包会默认携带memstats，该字段内含 各种内存堆栈以及 GC 的一些信息，具体可见源码正文
<details>
<summary>src/runtime/mstats.go</summary>
src/runtime/mstats.go
// A MemStats records statistics about the memory allocator.
type MemStats struct {
// General statistics.
// Alloc is bytes of allocated heap objects.
//
// This is the same as HeapAlloc (see below).
Alloc uint64
// TotalAlloc is cumulative bytes allocated for heap objects.
//
// TotalAlloc increases as heap objects are allocated, but
// unlike Alloc and HeapAlloc, it does not decrease when
// objects are freed.
TotalAlloc uint64
// Sys is the total bytes of memory obtained from the OS.
//
// Sys is the sum of the XSys fields below. Sys measures the
// virtual address space reserved by the Go runtime for the
// heap, stacks, and other internal data structures. It's
// likely that not all of the virtual address space is backed
// by physical memory at any given moment, though in general
// it all was at some point.
Sys uint64
// Lookups is the number of pointer lookups performed by the
// runtime.
//
// This is primarily useful for debugging runtime internals.
Lookups uint64
// Mallocs is the cumulative count of heap objects allocated.
// The number of live objects is Mallocs - Frees.
Mallocs uint64
// Frees is the cumulative count of heap objects freed.
Frees uint64
// Heap memory statistics.
//
// Interpreting the heap statistics requires some knowledge of
// how Go organizes memory. Go divides the virtual address
// space of the heap into "spans", which are contiguous
// regions of memory 8K or larger. A span may be in one of
// three states:
//
// An "idle" span contains no objects or other data. The
// physical memory backing an idle span can be released back
// to the OS (but the virtual address space never is), or it
// can be converted into an "in use" or "stack" span.
//
// An "in use" span contains at least one heap object and may
// have free space available to allocate more heap objects.
//
// A "stack" span is used for goroutine stacks. Stack spans
// are not considered part of the heap. A span can change
// between heap and stack memory; it is never used for both
// simultaneously.
// HeapAlloc is bytes of allocated heap objects.
//
// "Allocated" heap objects include all reachable objects, as
// well as unreachable objects that the garbage collector has
// not yet freed. Specifically, HeapAlloc increases as heap
// objects are allocated and decreases as the heap is swept
// and unreachable objects are freed. Sweeping occurs
// incrementally between GC cycles, so these two processes
// occur simultaneously, and as a result HeapAlloc tends to
// change smoothly (in contrast with the sawtooth that is
// typical of stop-the-world garbage collectors).
HeapAlloc uint64
// HeapSys is bytes of heap memory obtained from the OS.
//
// HeapSys measures the amount of virtual address space
// reserved for the heap. This includes virtual address space
// that has been reserved but not yet used, which consumes no
// physical memory, but tends to be small, as well as virtual
// address space for which the physical memory has been
// returned to the OS after it became unused (see HeapReleased
// for a measure of the latter).
//
// HeapSys estimates the largest size the heap has had.
HeapSys uint64
// HeapIdle is bytes in idle (unused) spans.
//
// Idle spans have no objects in them. These spans could be
// (and may already have been) returned to the OS, or they can
// be reused for heap allocations, or they can be reused as
// stack memory.
//
// HeapIdle minus HeapReleased estimates the amount of memory
// that could be returned to the OS, but is being retained by
// the runtime so it can grow the heap without requesting more
// memory from the OS. If this difference is significantly
// larger than the heap size, it indicates there was a recent
// transient spike in live heap size.
HeapIdle uint64
// HeapInuse is bytes in in-use spans.
//
// In-use spans have at least one object in them. These spans
// can only be used for other objects of roughly the same
// size.
//
// HeapInuse minus HeapAlloc estimates the amount of memory
// that has been dedicated to particular size classes, but is
// not currently being used. This is an upper bound on
// fragmentation, but in general this memory can be reused
// efficiently.
HeapInuse uint64
// HeapReleased is bytes of physical memory returned to the OS.
//
// This counts heap memory from idle spans that was returned
// to the OS and has not yet been reacquired for the heap.
HeapReleased uint64
// HeapObjects is the number of allocated heap objects.
//
// Like HeapAlloc, this increases as objects are allocated and
// decreases as the heap is swept and unreachable objects are
// freed.
HeapObjects uint64
// Stack memory statistics.
//
// Stacks are not considered part of the heap, but the runtime
// can reuse a span of heap memory for stack memory, and
// vice-versa.
// StackInuse is bytes in stack spans.
//
// In-use stack spans have at least one stack in them. These
// spans can only be used for other stacks of the same size.
//
// There is no StackIdle because unused stack spans are
// returned to the heap (and hence counted toward HeapIdle).
StackInuse uint64
// StackSys is bytes of stack memory obtained from the OS.
//
// StackSys is StackInuse, plus any memory obtained directly
// from the OS for OS thread stacks (which should be minimal).
StackSys uint64
// Off-heap memory statistics.
//
// The following statistics measure runtime-internal
// structures that are not allocated from heap memory (usually
// because they are part of implementing the heap). Unlike
// heap or stack memory, any memory allocated to these
// structures is dedicated to these structures.
//
// These are primarily useful for debugging runtime memory
// overheads.
// MSpanInuse is bytes of allocated mspan structures.
MSpanInuse uint64
// MSpanSys is bytes of memory obtained from the OS for mspan
// structures.
MSpanSys uint64
// MCacheInuse is bytes of allocated mcache structures.
MCacheInuse uint64
// MCacheSys is bytes of memory obtained from the OS for
// mcache structures.
MCacheSys uint64
// BuckHashSys is bytes of memory in profiling bucket hash tables.
BuckHashSys uint64
// GCSys is bytes of memory in garbage collection metadata.
GCSys uint64
// OtherSys is bytes of memory in miscellaneous off-heap
// runtime allocations.
OtherSys uint64
// Garbage collector statistics.
// NextGC is the target heap size of the next GC cycle.
//
// The garbage collector's goal is to keep HeapAlloc ≤ NextGC.
// At the end of each GC cycle, the target for the next cycle
// is computed based on the amount of reachable data and the
// value of GOGC.
NextGC uint64
// LastGC is the time the last garbage collection finished, as
// nanoseconds since 1970 (the UNIX epoch).
LastGC uint64
// PauseTotalNs is the cumulative nanoseconds in GC
// stop-the-world pauses since the program started.
//
// During a stop-the-world pause, all goroutines are paused
// and only the garbage collector can run.
PauseTotalNs uint64
// PauseNs is a circular buffer of recent GC stop-the-world
// pause times in nanoseconds.
//
// The most recent pause is at PauseNs[(NumGC+255)%256]. In
// general, PauseNs[N%256] records the time paused in the most
// recent N%256th GC cycle. There may be multiple pauses per
// GC cycle; this is the sum of all pauses during a cycle.
PauseNs [256]uint64
// PauseEnd is a circular buffer of recent GC pause end times,
// as nanoseconds since 1970 (the UNIX epoch).
//
// This buffer is filled the same way as PauseNs. There may be
// multiple pauses per GC cycle; this records the end of the
// last pause in a cycle.
PauseEnd [256]uint64
// NumGC is the number of completed GC cycles.
NumGC uint32
// NumForcedGC is the number of GC cycles that were forced by
// the application calling the GC function.
NumForcedGC uint32
// GCCPUFraction is the fraction of this program's available
// CPU time used by the GC since the program started.
//
// GCCPUFraction is expressed as a number between 0 and 1,
// where 0 means GC has consumed none of this program's CPU. A
// program's available CPU time is defined as the integral of
// GOMAXPROCS since the program started. That is, if
// GOMAXPROCS is 2 and a program has been running for 10
// seconds, its "available CPU" is 20 seconds. GCCPUFraction
// does not include CPU time used for write barrier activity.
//
// This is the same as the fraction of CPU reported by
// GODEBUG=gctrace=1.
GCCPUFraction float64
// EnableGC indicates that GC is enabled. It is always true,
// even if GOGC=off.
EnableGC bool
// DebugGC is currently unused.
DebugGC bool
// BySize reports per-size class allocation statistics.
//
// BySize[N] gives statistics for allocations of size S where
// BySize[N-1].Size < S ≤ BySize[N].Size.
//
// This does not report allocations larger than BySize[60].Size.
BySize [61]struct {
// Size is the maximum byte size of an object in this
// size class.
Size uint32
// Mallocs is the cumulative count of heap objects
// allocated in this size class. The cumulative bytes
// of allocation is Size*Mallocs. The number of live
// objects in this size class is Mallocs - Frees.
Mallocs uint64
// Frees is the cumulative count of heap objects freed
// in this size class.
Frees uint64
}
}</details>
对于各个字段的意义 可参考：
1、Alloc uint64 //Go 语言框架 堆空间调配的字节数
2、TotalAlloc uint64 // 从服务开始运行至今分配器为调配的堆空间总和，只减少，开释时不缩小
3、Sys uint64 // 服务当初应用的零碎内存
4、Lookups uint64 // 被 runtime 监督的指针数
5、Mallocs uint64 // 服务 malloc 的次数
6、Frees uint64 // 服务回收的 heap objects 的字节数
7、HeapAlloc uint64 // 服务调配的堆内存字节数
8、HeapSys uint64 // 零碎调配的作为运行栈的内存
9、HeapIdle uint64 // 申请但未调配的堆内存或者回收了的堆内存（闲暇）字节数
10、HeapInuse uint64 // 正在应用的堆内存字节数
10、HeapReleased uint64 // 返回给 OS 的堆内存，相似 C /C++ 中的 free
11、HeapObjects uint64 // 堆内存块申请的量
12、StackInuse uint64 // 正在应用的栈字节数
13、StackSys uint64 // 零碎调配的作为运行栈的内存
14、MSpanInuse uint64 // 用于测试用的构造体应用的字节数
15、MSpanSys uint64 // 零碎为测试用的构造体调配的字节数
16、MCacheInuse uint64 //mcache 构造体申请的字节数(不会被视为垃圾回收)
17、MCacheSys uint64 // 操作系统申请的堆空间用于 mcache 的字节数
18、BuckHashSys uint64 // 用于分析桶散列表的堆空间
19、GCSys uint64 // 垃圾回收标记元信息应用的内存
20、OtherSys uint64 //golang 零碎架构占用的额定空间
21、NextGC uint64 // 垃圾回收器检视的内存大小
22、LastGC uint64 // 垃圾回收器最初一次执行工夫。23、PauseTotalNs uint64 // 垃圾回收或者其余信息收集导致服务暂停的次数。24、PauseNs [256]uint64 // 一个循环队列，记录最近垃圾回收零碎中断的工夫
25、PauseEnd [256]uint64 // 一个循环队列，记录最近垃圾回收零碎中断的工夫开始点。26、NumForcedGC uint32 // 服务调用 runtime.GC()强制应用垃圾回收的次数。27、GCCPUFraction float64 // 垃圾回收占用服务 CPU 工作的工夫总和。如果有 100 个 goroutine，垃圾回收的工夫为 1S, 那么就占用了 100S。28、BySize // 内存分配器应用状况以上参考 golang 程序的监控神器 —-expvar
社区同行开发的 expvarmon 工具，能够在命令行终端以图形化的形式 实时展现特定的指标数据的变动，（expvarmon 即 expvar monitor）
go get github.com/divan/expvarmon
启动方才的程序，而后执行如下命令，可实时查看利用指标变动（期间能够进行不同 qps 的申请）
expvarmon -ports="http://localhost:6666/debug/vars" -i 1s
参考 给 expvarmon 插上数据长久化的“翅膀”
官网库或出名我的项目中的应用
src/net/http/triv.go 中应用了这个包
另外
golang.org/x/tools@v0.1.6/cmd/godoc/main.go
golang.org/x/tools@v0.1.6/go/internal/gccgoimporter/gccgoinstallation_test.go
go/test/bench/garbage/parser.go
也有应用
以及后面提到的 expvarmon
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