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我目前再RedHat工作，负责OpenShift 的测试工作，分享下OpenShift的Router是怎么工作的
首先说下k8s的service，大家都知道，k8s proxy 进程的目的是做service->pod的代理，支持两种方式，一种是在node上添加ip table rule， 为每一个service 启动一个tcp port 做监听，在node上写一条ip table rule ,将service Ip 的请求nat 到kube-proxy 为其代理的端口，然后代理请求servive的IP 通过一定算法将请求转发到Pod ，一种是直接将到Service ip的请求转发到pod， 通过iptable 的方式，为每一个endpoint添加ip table.
要想通过域名解析的方式访问pod的话，可以在DNS中将域名解析到service ip.openshift 的解决方案是利用haproxy 作为router，在每一个Node上启动一个haproxy 的pod，监听53端口，在DNS 服务器中将所有的域名解析请求转发到router pod 的node上，然后router pod，也就是haproxy再将请求转发到pod，这个过程完全无需人工操作。大概步骤如下：
1. 创建pod
2. 创建service
3.创建route，没个route都对应一个service，对应一个域名,可以直接从DeploymentConfig expose出来: oc expose dc/<dc_name>
4.openshift router controller，当然这个controller 运行在 haproxy的pod上，会监听service endpoint(service 对应的POD)的变化动态的修改haproxy 配置，当新创建一个route的时候，会再haproxy中添加对应的配置，当service endpoint增加或者删除或者状态不是ready的时候会修改ha-proxy配置以确保转发到健康的pod上面。
5. 目前每一个ha-proxy的配置文件都包括全网的域名解析的配置，有 user story 在做 route sharding,某一个router pod只解析某部分域名，从而减小route的配置文件的大小和满足不同域名需要不同的解析方式的需求
6. 当然，每一次pod的增减都去跟改配置和刷新haproxy配置文件会频繁的刷新haproxy 配置，目前也支持延迟刷新的功能，在一个周期内去刷新一次。
7. openshift不仅支持haproxy router, 还支持h5,详细请参考 https://docs.openshift.org/lat ... .html
8.更多route相关新功能请参考 https://trello.com/b/TV5P9gKe/networking
以下为一些resource的template 定义，贴到这作为参考。
[vagrant@ose ~]$ oc get service nodejs-example -o json
{
"kind": "Service",
"apiVersion": "v1",
"metadata": {"name": "nodejs-example","namespace": "haowang","selfLink": "/api/v1/namespaces/haowang/services/nodejs-example","uid": "1f832486-ef2e-11e5-bcc1-fa163efe3ad5","resourceVersion": "43606","creationTimestamp": "2016-03-21T06:28:28Z","labels": {"template": "nodejs-example"},"annotations": {"description": "Exposes and load balances the application pods"}
},
"spec": {"ports": [{"name": "web","protocol": "TCP","port": 8080,"targetPort": 8080}],"selector": {"name": "nodejs-example"},"portalIP": "172.31.174.255","clusterIP": "172.31.174.255","type": "ClusterIP","sessionAffinity": "None"
},
"status": {"loadBalancer": {}
}
}
[vagrant@ose ~]$ oc get route -o json
{
"kind": "List",
"apiVersion": "v1",
"metadata": {},
"items": [{"kind": "Route","apiVersion": "v1","metadata": {"name": "nodejs-example","namespace": "haowang","selfLink": "/oapi/v1/namespaces/haowang/routes/nodejs-example","uid": "1f80762b-ef2e-11e5-bcc1-fa163efe3ad5","resourceVersion": "43607","creationTimestamp": "2016-03-21T06:28:28Z","labels": {"template": "nodejs-example"},"annotations": {"openshift.io/host.generated": "true"}},"spec": {"host": "nodejs-example-haowang.0319-j7r.qe.rhcloud.com","to": {"kind": "Service","name": "nodejs-example"}},"status": {"ingress": [{"host": "nodejs-example-haowang.0319-j7r.qe.rhcloud.com","routerName": "router","conditions": [{"type": "Admitted","status": "True","lastTransitionTime": "2016-03-21T06:28:28Z"}]}]}}
]
}[vagrant@ose ~]$ oc get endpoints -o json
{
"kind": "List",
"apiVersion": "v1",
"metadata": {},
"items": [{"kind": "Endpoints","apiVersion": "v1","metadata": {"name": "nodejs-example","namespace": "haowang","selfLink": "/api/v1/namespaces/haowang/endpoints/nodejs-example","uid": "1f8d0087-ef2e-11e5-bcc1-fa163efe3ad5","resourceVersion": "44576","creationTimestamp": "2016-03-21T06:28:28Z","labels": {"template": "nodejs-example"}},"subsets": [{"addresses": [{"ip": "10.2.2.18","targetRef": {"kind": "Pod","namespace": "haowang","name": "nodejs-example-2-qagll","uid": "a73aedef-ef2f-11e5-bcc1-fa163efe3ad5","resourceVersion": "44570"}}],"ports": [{"name": "web","port": 8080,"protocol": "TCP"}]}]}
]
}