kubernetes中coredns组件的高级用法
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
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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#
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