Go env:

GOARCH="amd64"

GOBIN="/root/"

GOEXE=""

GOHOSTARCH="amd64"

GOHOSTOS="linux"

GOOS="linux"

GOPATH="/data/workspace/kubernetes"

GORACE=""

GOROOT="/usr/local/go"

GOTOOLDIR="/usr/local/go/pkg/tool/linux_amd64"

GO15VENDOREXPERIMENT="1"

CC="gcc"

GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0"

CXX="g++"

CGO_ENABLED="1"

Go version:

go version go1.6.3 linux/amd64

This issues is happend on a “performance test env” kube-apiserver with high load. kube-apiserver panic and exit:

fatal error: concurrent map read and map write

goroutine 77930636 [running]:
runtime.throw(0x2f4c4c0, 0x21)
    /root/.gvm/gos/go1.6.3/src/runtime/panic.go:547 +0x90 fp=0xca67b477f0     sp=0xca67b477d8
runtime.mapaccess1_faststr(0x2a8e520, 0xc9e29000f0, 0x2c11220, 0xa, 0x433e360)
    /root/.gvm/gos/go1.6.3/src/runtime/hashmap_fast.go:202 +0x5b fp=0xca67b47850 sp=0xca67b477f0
k8s.io/kubernetes/pkg/httplog.(*respLogger).Log(0xcbddf2ae70)
       /data/gerrit/src/k8s.io/kubernetes/_output/local/go/src/k8s.io/kubernetes/pkg/httplog/log.go:180 +0x43d fp=0xca67b47af8 sp=0xca67b47850
k8s.io/kubernetes/pkg/apiserver.RecoverPanics.func1(0x7f099f157090, 0xcbddf2ae70, 0xcd7569e380)
     /data/gerrit/src/k8s.io/kubernetes/_output/local/go/src/k8s.io/kubernetes/pkg/apiserver/handlers.go:174 +0x15d fp=0xca67b47b50 sp=0xca67b47af8
    net/http.HandlerFunc.ServeHTTP(0xc821a4eac0, 0x7f099f157058, 0xca0f4eb450, 0xcd7569e380)
    /root/.gvm/gos/go1.6.3/src/net/http/server.go:1618 +0x3a fp=0xca67b47b70 sp=0xca67b47b50
net/http.serverHandler.ServeHTTP(0xc8215a7b80, 0x7f099f157058, 0xca0f4eb450, 0xcd7569e380)
    /root/.gvm/gos/go1.6.3/src/net/http/server.go:2081 +0x19e fp=0xca67b47bd0 sp=0xca67b47b70
net/http.(*conn).serve(0xc8b5d6b980)
    /root/.gvm/gos/go1.6.3/src/net/http/server.go:1472 +0xf2e fp=0xca67b47f98 sp=0xca67b47bd0
runtime.goexit()
    /root/.gvm/gos/go1.6.3/src/runtime/asm_amd64.s:1998 +0x1 fp=0xca67b47fa0 sp=0xca67b47f98
created by net/http.(*Server).Serve
    /root/.gvm/gos/go1.6.3/src/net/http/server.go:2137 +0x44e

corresponding source code:

pkg/apiserver/handlers.go

145 func RecoverPanics(handler http.Handler) http.Handler {
146 return http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
147 defer func() {
148     if x := recover(); x != nil {
149         http.Error(w, "apis panic. Look in log for details.", http.StatusInternalServerError)
150         glog.Errorf("APIServer panic'd on %v %v: %v\n%s\n", req.Method, req.RequestURI, x, debug.Stack())
151     }
152 }()
153 defer httplog.NewLogged(req, &w).StacktraceWhen(
        httplog.StatusIsNot(
            http.StatusOK,
            http.StatusCreated,
            http.StatusAccepted,
            http.StatusBadRequest,
            http.StatusMovedPermanently,
            http.StatusTemporaryRedirect,
            http.StatusConflict,
            http.StatusNotFound,
            http.StatusUnauthorized,
            http.StatusForbidden,
            errors.StatusUnprocessableEntity,
            http.StatusSwitchingProtocols,
            http.StatusRequestTimeout,
            errors.StatusTooManyRequests,
        ),
170 ).Log()

    // Dispatch to the internal handler
    handler.ServeHTTP(w, req)
174 })
}

pkg/httplog/log.go:

159 func (rl *respLogger) Log() {
160 latency := time.Since(rl.startTime)
161 if glog.V(2) {
162     extraInfo := ""
163     if latency >= time.Millisecond*200 && latency < time.Second {
        extraInfo = fmt.Sprintf("%d00.Millisecond", latency/(time.Millisecond*100))
    } else if latency >= time.Second && latency < time.Minute { // Warning
        extraInfo = fmt.Sprintf("%d.Second", latency/(time.Second))
    } else if latency >= time.Minute { // nce will timeout
        extraInfo = fmt.Sprintf("%d.Minutes", latency/(time.Minute))
    }
    method := rl.req.Method
    if len(rl.req.Header["Detailed-Method"]) > 0 {
        method = rl.req.Header["Detailed-Method"][0]
    }

    remoteIP := rl.getXForwardIPAdress(rl.req)


    if !rl.hijacked {
        //glog.InfoDepth(1, fmt.Sprintf("%s %s: (%v) %v%v%v [%s %s]", rl.req.Method, rl.req.RequestURI, latency, rl.status, rl.statusStack, rl.addedInfo, rl.req.Header["User-Agent"], rl.req.RemoteAddr))
180         glog.InfoDepth(1, fmt.Sprintf("%v %s %s: (%sms) %v%v [%s %s]-%s %v", rl.req.Header["X-Requestid"], method, rl.req.RequestURI, GetMilliLatency(latency), rl.status, rl.addedInfo, rl.req.Header["User-Agent"], remoteIP, extraInfo, rl.statusStack))
    } else {
        //glog.InfoDepth(1, fmt.Sprintf("%s %s: (%v) hijacked [%s %s]", rl.req.Method, rl.req.RequestURI, latency, rl.req.Header["User-Agent"], rl.req.RemoteAddr))
        glog.InfoDepth(1, fmt.Sprintf("%v %s %s: (%sms) hijacked [%s %s]-%s", rl.req.Header["X-Requestid"], method, rl.req.RequestURI, GetMilliLatency(latency), rl.req.Header["User-Agent"], remoteIP, extraInfo))
    }
}

}

In handler.ServeHTTP, I changed request.Header. I cann't find the reason:

(1) "serveHTTP" and "defer log" works in a serial manner. So not exist "concurrent read and write"

(2) Even if exist "concurrent read and write", there exist "recover" func to deal with panics, so the kube-apiserver shoud not exit.

The question has cost me lots of time, who can help me? Thanks