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Merge pull request #5931 from WIZARD-CXY/updatehostportdoc 

update hostport doc
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Qiming 2017-11-28 10:00:19 +08:00 committed by GitHub
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docs/concepts/configuration/overview.md
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@ -39,7 +39,17 @@ This is a living document. If you think of something that is not on this list bu
- It's typically best to create a [service](/docs/concepts/services-networking/service/) before the corresponding [replication controllers](/docs/concepts/workloads/controllers/replicationcontroller/). This lets the scheduler spread the pods that comprise the service. - It's typically best to create a [service](/docs/concepts/services-networking/service/) before the corresponding [replication controllers](/docs/concepts/workloads/controllers/replicationcontroller/). This lets the scheduler spread the pods that comprise the service.
- Don't use `hostPort` unless it is absolutely necessary (for example: for a node daemon). It specifies the port number to expose on the host. When you bind a Pod to a `hostPort`, there are a limited number of places to schedule a pod due to port conflicts— you can only schedule as many such Pods as there are nodes in your Kubernetes cluster. - Don't use `hostPort` unless it is absolutely necessary (for example: for a node daemon).
It specifies the port number to expose on the host.
When you bind a Pod to a `hostPort`, there are a limited number of places to schedule a pod due to port conflicts.
The conflict comes from the requirement of an unique <hostIP,hostPort,protocol> combination.
Different <hostIP,hostPort,protocol> combinations mean different requirements.
For example, a pod that binds to host port 80 on 127.0.0.1 with TCP protocol has no conflict with another Pod that binds to host port 80 on 127.0.0.2 with TCP protocol.
*Special notes on hostIP and protocol*: If you don't specify the hostIP and protocol explicitly,
kubernetes will use 0.0.0.0 and TCP as the default hostIP and protocol,
where "0.0.0.0" is a wildcard IP that will match all <*,hostPort,protocol> on the node the pod is scheduled on.
Specifically, it will match all <IP,hostPort,protocol> tuples for all IPs on the host.
If you only need access to the port for debugging purposes, you can use the [kubectl proxy and apiserver proxy](/docs/tasks/access-kubernetes-api/http-proxy-access-api/) or [kubectl port-forward](/docs/tasks/access-application-cluster/port-forward-access-application-cluster/). If you only need access to the port for debugging purposes, you can use the [kubectl proxy and apiserver proxy](/docs/tasks/access-kubernetes-api/http-proxy-access-api/) or [kubectl port-forward](/docs/tasks/access-application-cluster/port-forward-access-application-cluster/).
You can use a [Service](/docs/concepts/services-networking/service/) object for external service access. You can use a [Service](/docs/concepts/services-networking/service/) object for external service access.