kubernetes中coredns组件的高级用法-创新互联

通过coredns实现内外流量分离

场景

旧业务固定了域名，无法通过内部service直接访问服务
需要实现内部流量和外部流量自动拆分

实现

通过coredns的rewrite功能实现以上能力,如以下内部访问tenant.msa.chinamcloud.com域名时，会将流量转发到tenantapi.yunjiao.svc.cluster.local域名，实现内外域名访问一致。
部分版本nginx配置时候可能遇见无法访问的情况

[root@k8s-master1 ingress]# cat coredns.yaml
apiVersion: v1
data:
  Corefile: |
    .:53 {
        errors
        health
        rewrite name tenant.msa.chinamcloud.com tenantapi.yunjiao.svc.cluster.local
        rewrite name console.msa.chinamcloud.com console.yunjiao.svc.cluster.local
        rewrite name user.msa.chinamcloud.com userapi.yunjiao.svc.cluster.local
        rewrite name lims.msa.chinamcloud.com lims.yunjiao.svc.cluster.local
        rewrite name labapp.msa.chinamcloud.com limsapp.yunjiao.svc.cluster.local
        kubernetes cluster.local in-addr.arpa ip6.arpa {
           pods insecure
           upstream
           fallthrough in-addr.arpa ip6.arpa
        }
        prometheus :9153
        forward . /etc/resolv.conf
        cache 30
        loop
        reload
        loadbalance
    }
kind: ConfigMap
metadata:
  creationTimestamp: "2019-04-02T04:57:19Z"
  name: coredns
  namespace: kube-system
  resourceVersion: "197"
  selfLink: /api/v1/namespaces/kube-system/configmaps/coredns
  uid: cb686453-5503-11e9-8ea6-005056be93f5

检查

[root@k8s-master1 ingress]#  kubectl run -it --rm --restart=Never --image=infoblox/dnstools:latest dnstools
If you don't see a command prompt, try pressing enter.
dnstools# ping tenant.msa.chinamcloud.com
PING tenant.msa.chinamcloud.com (10.98.220.54): 56 data bytes
^C
--- tenant.msa.chinamcloud.com ping statistics ---
4 packets transmitted, 0 packets received, 100% packet loss

kubernetes内部实现hosts功能

coredns配置参考文档

10年积累的成都网站制作、成都网站建设、外贸营销网站建设经验，可以快速应对客户对网站的新想法和需求。提供各种问题对应的解决方案。让选择我们的客户得到更好、更有力的网络服务。我虽然不认识你，你也不认识我。但先制作网站后付款的网站建设流程，更有郸城免费网站建设让你可以放心的选择与我们合作。

场景

通过kubernetes的coredns实现子域名解析
实现kubernetes内部 hosts绑定功能

实现

创建pod时声明hosts(不推荐)

[root@k8s-master-1 coredns]# kubectl  explain  pods.spec.hostAliases
KIND:     Pod
VERSION:  v1

RESOURCE: hostAliases <[]Object>

DESCRIPTION:
     HostAliases is an optional list of hosts and IPs that will be injected into
     the pod's hosts file if specified. This is only valid for non-hostNetwork
     pods.

     HostAlias holds the mapping between IP and hostnames that will be injected
     as an entry in the pod's hosts file.

FIELDS:
   hostnames    <[]string>
     Hostnames for the above IP address.

   ip   
     IP address of the host file entry.

[root@k8s-master-1 coredns]#

coredns的hosts特性声明

hosts 字段部分指明了三个域名的解析地址

[root@k8s-master-1 coredns]# cat coredns-cm.yaml
apiVersion: v1
data:
  Corefile: |
    .:53 {
        errors
        health
        hosts {
            100.64.139.66 minio.chinamcloud.com
            100.64.139.66 registry.chinamcloud.com
            100.64.139.66 gitlab.chinamcloud.com
            fallthrough
        }
        kubernetes cluster.local in-addr.arpa ip6.arpa {
           pods insecure
           upstream
           fallthrough in-addr.arpa ip6.arpa
        }
        prometheus :9153
        forward . /etc/resolv.conf
        cache 30
        loop
        reload
        loadbalance
    }
kind: ConfigMap
metadata:
  name: coredns
  namespace: kube-system

根据域名指定上游dns服务器

sobeydemo.com 字段指明了解析该域名的dns服务器地址

[root@k8s-master-1 coredns]# cat coredns-cm.yaml
apiVersion: v1
data:
  Corefile: |
    .:53 {
        errors
        health
        kubernetes cluster.local in-addr.arpa ip6.arpa {
           pods insecure
           upstream
           fallthrough in-addr.arpa ip6.arpa
        }
        prometheus :9153
        forward . /etc/resolv.conf
        cache 30
        loop
        reload
        loadbalance
    }
    sobeydemo.com {
        forward . 100.64.134.250:53
    }
kind: ConfigMap
metadata:
  name: coredns
  namespace: kube-system

检查

[root@k8s-master-1 coredns]#  kubectl run -it --rm --restart=Never --image=infoblox/dnstools:latest dnstools
If you don't see a command prompt, try pressing enter.
dnstools# host 0DJ01YUR.sobeydemo.com
0DJ01YUR.sobeydemo.com has address 100.64.148.116
0DJ01YUR.sobeydemo.com has IPv6 address 2002:6440:9474::6440:9474
dnstools# host minio.chinamcloud.com
minio.chinamcloud.com has address 100.64.139.66
Host minio.chinamcloud.com not found: 3(NXDOMAIN)
Host minio.chinamcloud.com not found: 3(NXDOMAIN)
dnstools#

另外有需要云服务器可以了解下创新互联cdcxhl.cn，海内外云服务器15元起步，三天无理由+7*72小时售后在线，公司持有idc许可证，提供“云服务器、裸金属服务器、高防服务器、香港服务器、美国服务器、虚拟主机、免备案服务器”等云主机租用服务以及企业上云的综合解决方案，具有“安全稳定、简单易用、服务可用性高、性价比高”等特点与优势，专为企业上云打造定制，能够满足用户丰富、多元化的应用场景需求。

分享标题：kubernetes中coredns组件的高级用法-创新互联
分享网址：http://mswzjz.cn/article/edhei.html

网站建设知识