K8S 内部服务调用域名解析超时

            package main

import (
    "context"
    "flag"
    "fmt"
    "net"
    "sync/atomic"
    "time"
)

var host string
var connections int
var duration int64
var limit int64
var timeoutCount int64

func main() {
    // os.Args = append(os.Args, "-host", "www.baidu.com", "-c", "200", "-d", "30", "-l", "5000")

    flag.StringVar(&host, "host", "", "Resolve host")
    flag.IntVar(&connections, "c", 100, "Connections")
    flag.Int64Var(&duration, "d", 0, "Duration(s)")
    flag.Int64Var(&limit, "l", 0, "Limit(ms)")
    flag.Parse()

    var count int64 = 0
    var errCount int64 = 0
    pool := make(chan interface{}, connections)
    exit := make(chan bool)
    var (
        min int64 = 0
        max int64 = 0
        sum int64 = 0
    )

    go func() {
        time.Sleep(time.Second * time.Duration(duration))
        exit <- true
    }()
endD:
    for {
        select {
        case pool <- nil:
            go func() {
                defer func() {
                    <-pool
                }()
                resolver := &net.Resolver{}
                now := time.Now()
                _, err := resolver.LookupIPAddr(context.Background(), host)
                use := time.Since(now).Nanoseconds() / int64(time.Millisecond)
                if min == 0 || use < min {
                    min = use
                }
                if use > max {
                    max = use
                }
                sum += use
                if limit > 0 && use >= limit {
                    timeoutCount++
                }
                atomic.AddInt64(&count, 1)
                if err != nil {
                    fmt.Println(err.Error())
                    atomic.AddInt64(&errCount, 1)
                }
            }()
        case <-exit:
            break endD
        }
    }

    fmt.Printf("request count：%d\nerror count：%d\n", count, errCount)
    fmt.Printf("request time：min(%dms) max(%dms) avg(%dms) timeout(%dn)\n", min, max, sum/count, timeoutCount)
}
        

            # 200个并发,持续30秒
./dns -host {service}.{namespace} -c 200 -d 30
        

            lifecycle:
  postStart:
    exec:
      command:
        - /bin/sh
        - -c
        - "/bin/echo ‘options single-request-reopen‘ >> /etc/resolv.conf"
        

            template:
  spec:
    dnsConfig:
      options:
        - name: single-request-reopen
        

            # kubectl -n kube-system get svc kube-dns -o jsonpath="{.spec.clusterIP}"
10.96.0.10
        

            wget -O nodelocaldns.yaml "https://github.com/kubernetes/kubernetes/raw/master/cluster/addons/dns/nodelocaldns/nodelocaldns.yaml" && sed -i ‘s/__PILLAR__DNS__SERVER__/10.96.0.10/g‘ nodelocaldns.yaml && sed -i ‘s/__PILLAR__LOCAL__DNS__/169.254.20.10/g‘ nodelocaldns.yaml && sed -i ‘s/__PILLAR__DNS__DOMAIN__/cluster.local/g‘ nodelocaldns.yaml && sed -i ‘s/__PILLAR__CLUSTER__DNS__/10.96.0.10/g‘ nodelocaldns.yaml && sed -i ‘s/__PILLAR__UPSTREAM__SERVERS__/\/etc\/resolv.conf/g‘ nodelocaldns.yaml
        

            # Copyright 2018 The Kubernetes Authors.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#

apiVersion: v1
kind: ServiceAccount
metadata:
  name: node-local-dns
  namespace: kube-system
  labels:
    kubernetes.io/cluster-service: "true"
    addonmanager.kubernetes.io/mode: Reconcile
---
apiVersion: v1
kind: Service
metadata:
  name: kube-dns-upstream
  namespace: kube-system
  labels:
    k8s-app: kube-dns
    kubernetes.io/cluster-service: "true"
    addonmanager.kubernetes.io/mode: Reconcile
    kubernetes.io/name: "KubeDNSUpstream"
spec:
  ports:
    - name: dns
      port: 53
      protocol: UDP
      targetPort: 53
    - name: dns-tcp
      port: 53
      protocol: TCP
      targetPort: 53
  selector:
    k8s-app: kube-dns
---
apiVersion: v1
kind: ConfigMap
metadata:
  name: node-local-dns
  namespace: kube-system
  labels:
    addonmanager.kubernetes.io/mode: Reconcile
data:
  Corefile: |
    cluster.local:53 {
        errors
        cache {
                success 9984 30
                denial 9984 5
        }
        reload
        loop
        bind 169.254.20.10 10.96.0.10
        forward . 10.96.0.10 {
                force_tcp
        }
        prometheus :9253
        health 169.254.20.10:8080
        }
    in-addr.arpa:53 {
        errors
        cache 30
        reload
        loop
        bind 169.254.20.10 10.96.0.10
        forward . 10.96.0.10 {
                force_tcp
        }
        prometheus :9253
        }
    ip6.arpa:53 {
        errors
        cache 30
        reload
        loop
        bind 169.254.20.10 10.96.0.10
        forward . 10.96.0.10 {
                force_tcp
        }
        prometheus :9253
        }
    .:53 {
        errors
        cache 30
        reload
        loop
        bind 169.254.20.10 10.96.0.10
        forward . /etc/resolv.conf {
                force_tcp
        }
        prometheus :9253
        }
---
apiVersion: apps/v1
kind: DaemonSet
metadata:
  name: node-local-dns
  namespace: kube-system
  labels:
    k8s-app: node-local-dns
    kubernetes.io/cluster-service: "true"
    addonmanager.kubernetes.io/mode: Reconcile
spec:
  updateStrategy:
    rollingUpdate:
      maxUnavailable: 10%
  selector:
    matchLabels:
      k8s-app: node-local-dns
  template:
    metadata:
      labels:
        k8s-app: node-local-dns
    spec:
      priorityClassName: system-node-critical
      serviceAccountName: node-local-dns
      hostNetwork: true
      dnsPolicy: Default # Don‘t use cluster DNS.
      tolerations:
        - key: "CriticalAddonsOnly"
          operator: "Exists"
      containers:
        - name: node-cache
          image: k8s.gcr.io/k8s-dns-node-cache:1.15.7
          resources:
            requests:
              cpu: 25m
              memory: 5Mi
          args:
            [
              "-localip",
              "169.254.20.10,10.96.0.10",
              "-conf",
              "/etc/Corefile",
              "-upstreamsvc",
              "kube-dns-upstream",
            ]
          securityContext:
            privileged: true
          ports:
            - containerPort: 53
              name: dns
              protocol: UDP
            - containerPort: 53
              name: dns-tcp
              protocol: TCP
            - containerPort: 9253
              name: metrics
              protocol: TCP
          livenessProbe:
            httpGet:
              host: 169.254.20.10
              path: /health
              port: 8080
            initialDelaySeconds: 60
            timeoutSeconds: 5
          volumeMounts:
            - mountPath: /run/xtables.lock
              name: xtables-lock
              readOnly: false
            - name: config-volume
              mountPath: /etc/coredns
            - name: kube-dns-config
              mountPath: /etc/kube-dns
      volumes:
        - name: xtables-lock
          hostPath:
            path: /run/xtables.lock
            type: FileOrCreate
        - name: kube-dns-config
          configMap:
            name: kube-dns
            optional: true
        - name: config-volume
          configMap:
            name: node-local-dns
            items:
              - key: Corefile
                path: Corefile.base
        

            template:
  spec:
    dnsConfig:
      nameservers:
        - 169.254.20.10
      searches:
        - public.svc.cluster.local
        - svc.cluster.local
        - cluster.local
      options:
        - name: ndots
        value: "5"
    dnsPolicy: None
        

            systemctl restart kubelet