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Merge pull request #31331 from yashodhanmohan/feat/docker-cleanup 

Clean up docker references from Service documentations
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Kubernetes Prow Robot 2022-02-01 07:21:12 -08:00 committed by GitHub
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content/en/docs/concepts/services-networking/connect-applications-service.md
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@ -13,11 +13,9 @@ weight: 30
## The Kubernetes model for connecting containers ## The Kubernetes model for connecting containers
Now that you have a continuously running, replicated application you can expose it on a network. Before discussing the Kubernetes approach to networking, it is worthwhile to contrast it with the "normal" way networking works with Docker. Now that you have a continuously running, replicated application you can expose it on a network.
By default, Docker uses host-private networking, so containers can talk to other containers only if they are on the same machine. In order for Docker containers to communicate across nodes, there must be allocated ports on the machine's own IP address, which are then forwarded or proxied to the containers. This obviously means that containers must either coordinate which ports they use very carefully or ports must be allocated dynamically. Kubernetes assumes that pods can communicate with other pods, regardless of which host they land on. Kubernetes gives every pod its own cluster-private IP address, so you do not need to explicitly create links between pods or map container ports to host ports. This means that containers within a Pod can all reach each other's ports on localhost, and all pods in a cluster can see each other without NAT. The rest of this document elaborates on how you can run reliable services on such a networking model.
Coordinating port allocations across multiple developers or teams that provide containers is very difficult to do at scale, and exposes users to cluster-level issues outside of their control. Kubernetes assumes that pods can communicate with other pods, regardless of which host they land on. Kubernetes gives every pod its own cluster-private IP address, so you do not need to explicitly create links between pods or map container ports to host ports. This means that containers within a Pod can all reach each other's ports on localhost, and all pods in a cluster can see each other without NAT. The rest of this document elaborates on how you can run reliable services on such a networking model.
This guide uses a simple nginx server to demonstrate proof of concept. This guide uses a simple nginx server to demonstrate proof of concept.
@ -52,7 +50,7 @@ kubectl get pods -l run=my-nginx -o yaml | grep podIP
podIP: 10.244.2.5 podIP: 10.244.2.5
``` ```
You should be able to ssh into any node in your cluster and curl both IPs. Note that the containers are *not* using port 80 on the node, nor are there any special NAT rules to route traffic to the pod. This means you can run multiple nginx pods on the same node all using the same containerPort and access them from any other pod or node in your cluster using IP. Like Docker, ports can still be published to the host node's interfaces, but the need for this is radically diminished because of the networking model. You should be able to ssh into any node in your cluster and use a tool such as `curl` to make queries against both IPs. Note that the containers are *not* using port 80 on the node, nor are there any special NAT rules to route traffic to the pod. This means you can run multiple nginx pods on the same node all using the same `containerPort`, and access them from any other pod or node in your cluster using the assigned IP address for the Service. If you want to arrange for a specific port on the host Node to be forwarded to backing Pods, you can - but the networking model should mean that you do not need to do so.
You can read more about the [Kubernetes Networking Model](/docs/concepts/cluster-administration/networking/#the-kubernetes-network-model) if you're curious. You can read more about the [Kubernetes Networking Model](/docs/concepts/cluster-administration/networking/#the-kubernetes-network-model) if you're curious.

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content/en/docs/concepts/services-networking/service.md
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@ -450,10 +450,7 @@ variables and DNS.
### Environment variables ### Environment variables
When a Pod is run on a Node, the kubelet adds a set of environment variables When a Pod is run on a Node, the kubelet adds a set of environment variables
for each active Service. It supports both [Docker links for each active Service. It adds `{SVCNAME}_SERVICE_HOST` and `{SVCNAME}_SERVICE_PORT` variables, where the Service name is upper-cased and dashes are converted to underscores. It also supports variables (see [makeLinkVariables](https://github.com/kubernetes/kubernetes/blob/dd2d12f6dc0e654c15d5db57a5f9f6ba61192726/pkg/kubelet/envvars/envvars.go#L72)) that are compatible with Docker Engine's "_[legacy container links](https://docs.docker.com/network/links/)_" feature.
compatible](https://docs.docker.com/userguide/dockerlinks/) variables (see [makeLinkVariables](https://github.com/kubernetes/kubernetes/blob/dd2d12f6dc0e654c15d5db57a5f9f6ba61192726/pkg/kubelet/envvars/envvars.go#L72))
and simpler `{SVCNAME}_SERVICE_HOST` and `{SVCNAME}_SERVICE_PORT` variables,
where the Service name is upper-cased and dashes are converted to underscores.
For example, the Service `redis-master` which exposes TCP port 6379 and has been For example, the Service `redis-master` which exposes TCP port 6379 and has been
allocated cluster IP address 10.0.0.11, produces the following environment allocated cluster IP address 10.0.0.11, produces the following environment