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获取Goroutine的ID

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在Golang的FAQ中，解释了为什么goroutine是匿名的，没有暴露出ID等状态信息，主要是因为如果一个特定的goroutine有了名字(ID)，开发者就会忽略使用多个goroutine来处理信息的可能，从而限制库的使用。

但是，有时候开发者也需要获取goroutine来进行特定的操作。本文介绍如何从堆栈信息中获取goroutine信息。

panic获取堆栈信息

当go程序panic的时候，会打印出goroutine的ID, 状态，函数，调用栈的信息。

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func TestPanic(t *testing.T){
	panic("get stack info")
}

堆栈信息

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goroutine 18 [running]:
testing.tRunner.func1.1(0x111b7e0, 0x116c710)
	/usr/local/go/src/testing/testing.go:1076 +0x30d
testing.tRunner.func1(0xc000082600)
	/usr/local/go/src/testing/testing.go:1079 +0x41a
panic(0x111b7e0, 0x116c710)
	/usr/local/go/src/runtime/panic.go:969 +0x175
awesomeProject/goid.TestPanic(0xc000082600)
	/Users/liangyaopei/go/src/awesomeProject/goid/goid_test.go:6 +0x39
testing.tRunner(0xc000082600, 0x114d490)
	/usr/local/go/src/testing/testing.go:1127 +0xef
created by testing.(*T).Run
	/usr/local/go/src/testing/testing.go:1178 +0x38

可以看到，goroutine的ID是18，当前状态是running，调用的函数是testing.tRunner.func1。

goroutine的状态

在/runtime/traceback.go中，可以看到goroutine一共有以下的状态:

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var gStatusStrings = [...]string{
	_Gidle:      "idle",
	_Grunnable:  "runnable",
	_Grunning:   "running",
	_Gsyscall:   "syscall",
	_Gwaiting:   "waiting",
	_Gdead:      "dead",
	_Gcopystack: "copystack",
	_Gpreempted: "preempted",
}

runtime.Stack获取堆栈信息

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package runtime

// Stack formats a stack trace of the calling goroutine into buf
// and returns the number of bytes written to buf.
// If all is true, Stack formats stack traces of all other goroutines
// into buf after the trace for the current goroutine.
func Stack(buf []byte, all bool) int {
    if all {
		stopTheWorld("stack trace")
	}
    ...
    if all {
		startTheWorld()
	}
}

runtime.Stack(),接受2个参数，一个是保存信息的字符串数字，另一个all表示是否要打印全部的堆栈信息。如果all为true，就会先调用stopTheWorld
看下面的测试:

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func TestGetStackInfo(t *testing.T) {
	var (
		size = 64 * 1024
		all  = false
	)
	buf := make([]byte, size)
	runtime.Stack(buf, all)
	t.Logf("%s", string(buf))
}

输入结果:

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goid_test.go:19: goroutine 18 [running]:
       awesomeProject/goid.TestGetStackInfo(0xc000082600)
       	/Users/liangyaopei/go/src/awesomeProject/goid/goid_test.go:18 +0x6f
       testing.tRunner(0xc000082600, 0x114d5c0)
       	/usr/local/go/src/testing/testing.go:1127 +0xef
       created by testing.(*T).Run
       	/usr/local/go/src/testing/testing.go:1178 +0x386

可以看到，输入的结果都是有格式的。

解析堆栈信息，获取goroutine ID

在stack.go中，通过调用runtime.Stack函数，获取当前的堆栈信息，然后解析。

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// GetInfo returns goroutine stack information.
// Stack information includes id, state, firstFunction,fullStack and timestamp.
func GetInfo(all bool) []Stack {
	var stacks []Stack

	var curStack *Stack
	stackReader := bufio.NewReader(bytes.NewReader(getStackBuffer(all)))
	for {
		line, err := stackReader.ReadString('\n')
		if err == io.EOF {
			break
		}
		if err != nil {
			panic("bufio.NewReader failed on a fixed string")
		}
		// If we see the goroutine header, start a new stack.
		isFirstLine := false
		if strings.HasPrefix(line, "goroutine ") {
			// flush any previous stack
			if curStack != nil {
				stacks = append(stacks, *curStack)
			}
			id, goState := parseGoStackHeader(line)
			curStack = &Stack{
				id:        id,
				state:     goState,
				fullStack: &bytes.Buffer{},
				timeStamp: time.Now().UnixNano(),
			}
			isFirstLine = true
		}
		curStack.fullStack.WriteString(line)
		if !isFirstLine && curStack.firstFunction == "" {
			curStack.firstFunction = parseFirstFunc(line)
		}
	}
	if curStack != nil {
		stacks = append(stacks, *curStack)
	}
	return stacks
}

通过解析以下的信息格式，获取对于的id。

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xxx.go:19: goroutine xx [xx]:

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