介绍与使用
expvar 是 exposed variable的简写
expvar包是 Golang 官方为暴露Go应用内部指标数据所提供的标准对外接口，可以辅助获取和调试全局变量。
其通过init函数将内置的expvarHandler(一个标准http HandlerFunc)注册到http包ListenAndServe创建的默认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{}
// 开始时间
var start = time.Now()
// calculateUptime 计算运行时间
func calculateUptime() interface{} {
return time.Since(start).String()
}
// currentGoVersion 当前 Golang 版本
func currentGoVersion() interface{} {
return runtime.Version()
}
// getNumCPUs 获取 CPU 核心数量
func getNumCPUs() interface{} {
return runtime.NumCPU()
}
// getGoOS 当前系统类型
func getGoOS() interface{} {
return runtime.GOOS
}
// getNumGoroutins 当前 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 的暂停时间
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 返回当前运行信息
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，发布到expvar中，每次请求接口，expvar会自动去获取这些变量，并返回
expvar.Publish("运行时间", 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，并请求127.0.0.1:6666/debug/vars
<details>
<summary>结果如下：</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",
"运行时间": "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，具体可见源码注释
<details>
<summary>src/runtime/mstats.go</summary>
// 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 堆空间分配的字节数
2、TotalAlloc uint64 //从服务开始运行至今分配器为分配的堆空间总和，只增加，释放时不减少
3、Sys uint64 //服务现在使用的系统内存
4、Lookups uint64 //被runtime监视的指针数
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 //服务分配的堆内存字节数
8、HeapSys uint64 //系统分配的作为运行栈的内存
9、HeapIdle uint64 //申请但未分配的堆内存或者回收了的堆内存（空闲）字节数
10、HeapInuse uint64 //正在使用的堆内存字节数
10、HeapReleased uint64 //返回给OS的堆内存，类似C/C++中的free
11、HeapObjects uint64 //堆内存块申请的量
12、StackInuse uint64 //正在使用的栈字节数
13、StackSys uint64 //系统分配的作为运行栈的内存
14、MSpanInuse uint64 //用于测试用的结构体使用的字节数
15、MSpanSys uint64 //系统为测试用的结构体分配的字节数
16、MCacheInuse uint64 //mcache结构体申请的字节数(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 //用于剖析桶散列表的堆空间
19、GCSys uint64 //垃圾回收标记元信息使用的内存
20、OtherSys uint64 //golang系统架构占用的额外空间
21、NextGC uint64 //垃圾回收器检视的内存大小
22、LastGC uint64 // 垃圾回收器最后一次执行时间。
23、PauseTotalNs uint64 // 垃圾回收或者其他信息收集导致服务暂停的次数。
24、PauseNs [256]uint64 //一个循环队列，记录最近垃圾回收系统中断的时间
25、PauseEnd [256]uint64 //一个循环队列，记录最近垃圾回收系统中断的时间开始点。
26、NumForcedGC uint32 //服务调用runtime.GC()强制使用垃圾回收的次数。
27、GCCPUFraction float64 //垃圾回收占用服务CPU工作的时间总和。如果有100个goroutine，垃圾回收的时间为1S,那么就占用了100S。
28、BySize //内存分配器使用情况社区同行开发的expvarmon工具，可以在命令行终端以图形化的方式实时展示特定的指标数据的变化，（expvarmon 即expvar monitor）
go get github.com/divan/expvarmon
启动刚才的程序，然后执行如下命令，可实时查看应用指标变化 （期间可以进行不同qps的请求）
expvarmon -ports="http://localhost:6666/debug/vars" -i 1s
官方库或知名项目中的使用
src/net/http/triv.go 中使用了这个包
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
也有使用
以及前面提到的expvarmon
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