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Merge pull request #2204 from steveperry-53/env-yaml

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Fix link.
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Steve Perry
2017-01-17 16:22:29 -08:00
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title: Using Environment Variables title: Using Environment Variables
--- ---
This example demonstrates running pods, replication controllers, and This example demonstrates running pods, replication controllers, and
services. It shows two types of pods: frontend and backend, with services. It shows two types of pods: frontend and backend, with
services on top of both. Accessing the frontend pod will return services on top of both. Accessing the frontend pod will return
environment information about itself, and a backend pod that it has environment information about itself, and a backend pod that it has
accessed through the service. The goal is to illuminate the accessed through the service. The goal is to illuminate the
environment metadata available to running containers inside the environment metadata available to running containers inside the
Kubernetes cluster. The documentation for the Kubernetes environment Kubernetes cluster. The documentation for the Kubernetes environment
is [here](/docs/user-guide/container-environment). is [here](/docs/user-guide/container-environment).
![Diagram](/images/docs/diagram.png) ![Diagram](/images/docs/diagram.png)
## Prerequisites ## Prerequisites
This example assumes that you have a Kubernetes cluster installed and This example assumes that you have a Kubernetes cluster installed and
running, and that you have installed the `kubectl` command line tool running, and that you have installed the `kubectl` command line tool
somewhere in your path. Please see the [getting somewhere in your path. Please see the [getting
started](/docs/getting-started-guides/) for installation instructions started](/docs/getting-started-guides/) for installation instructions
for your platform. for your platform.
## Optional: Build your own containers ## Optional: Build your own containers
The code for the containers is under These are the configuration files for the containers:
[containers/](/docs/user-guide/containers/)
* [backend-rc.yaml](https://raw.githubusercontent.com/kubernetes/kubernetes.github.io/master/docs/user-guide/environment-guide/backend-rc.yaml)
## Get everything running * [backend-srv.yaml](https://raw.githubusercontent.com/kubernetes/kubernetes.github.io/master/docs/user-guide/environment-guide/backend-srv.yaml)
* [show-rc.yaml](https://raw.githubusercontent.com/kubernetes/kubernetes.github.io/master/docs/user-guide/environment-guide/show-rc.yaml)
```shell * [show-srv.yaml](https://raw.githubusercontent.com/kubernetes/kubernetes.github.io/master/docs/user-guide/environment-guide/show-srv.yaml)
kubectl create -f ./backend-rc.yaml
kubectl create -f ./backend-srv.yaml ## Get everything running
kubectl create -f ./show-rc.yaml
kubectl create -f ./show-srv.yaml ```shell
``` kubectl create -f ./backend-rc.yaml
kubectl create -f ./backend-srv.yaml
## Query the service kubectl create -f ./show-rc.yaml
kubectl create -f ./show-srv.yaml
Use `kubectl describe service show-srv` to determine the public IP of ```
your service.
## Query the service
> Note: If your platform does not support external load balancers,
you'll need to open the proper port and direct traffic to the Use `kubectl describe service show-srv` to determine the public IP of
internal IP shown for the frontend service with the above command your service.
Run `curl <public ip>:80` to query the service. You should get > Note: If your platform does not support external load balancers,
something like this back: you'll need to open the proper port and direct traffic to the
internal IP shown for the frontend service with the above command
```shell
Pod Name: show-rc-xxu6i Run `curl <public ip>:80` to query the service. You should get
Pod Namespace: default something like this back:
USER_VAR: important information
```shell
Kubernetes environment variables Pod Name: show-rc-xxu6i
BACKEND_SRV_SERVICE_HOST = 10.147.252.185 Pod Namespace: default
BACKEND_SRV_SERVICE_PORT = 5000 USER_VAR: important information
KUBERNETES_RO_SERVICE_HOST = 10.147.240.1
KUBERNETES_RO_SERVICE_PORT = 80 Kubernetes environment variables
KUBERNETES_SERVICE_HOST = 10.147.240.2 BACKEND_SRV_SERVICE_HOST = 10.147.252.185
KUBERNETES_SERVICE_PORT = 443 BACKEND_SRV_SERVICE_PORT = 5000
KUBE_DNS_SERVICE_HOST = 10.147.240.10 KUBERNETES_RO_SERVICE_HOST = 10.147.240.1
KUBE_DNS_SERVICE_PORT = 53 KUBERNETES_RO_SERVICE_PORT = 80
KUBERNETES_SERVICE_HOST = 10.147.240.2
Found backend ip: 10.147.252.185 port: 5000 KUBERNETES_SERVICE_PORT = 443
Response from backend KUBE_DNS_SERVICE_HOST = 10.147.240.10
Backend Container KUBE_DNS_SERVICE_PORT = 53
Backend Pod Name: backend-rc-6qiya
Backend Namespace: default Found backend ip: 10.147.252.185 port: 5000
``` Response from backend
Backend Container
First the frontend pod's information is printed. The pod name and Backend Pod Name: backend-rc-6qiya
[namespace](https://github.com/kubernetes/kubernetes/blob/{{page.githubbranch}}/docs/design/namespaces.md) are retrieved from the Backend Namespace: default
[Downward API](/docs/user-guide/downward-api). Next, `USER_VAR` is the name of ```
an environment variable set in the [pod
definition](/docs/user-guide/environment-guide/show-rc.yaml). Then, the dynamic Kubernetes environment First the frontend pod's information is printed. The pod name and
variables are scanned and printed. These are used to find the backend [namespace](https://github.com/kubernetes/kubernetes/blob/{{page.githubbranch}}/docs/design/namespaces.md) are retrieved from the
service, named `backend-srv`. Finally, the frontend pod queries the [Downward API](/docs/user-guide/downward-api). Next, `USER_VAR` is the name of
backend service and prints the information returned. Again the backend an environment variable set in the [pod
pod returns its own pod name and namespace. definition](/docs/user-guide/environment-guide/show-rc.yaml). Then, the dynamic Kubernetes environment
variables are scanned and printed. These are used to find the backend
Try running the `curl` command a few times, and notice what service, named `backend-srv`. Finally, the frontend pod queries the
changes. Ex: `watch -n 1 curl -s <ip>` Firstly, the frontend service backend service and prints the information returned. Again the backend
is directing your request to different frontend pods each time. The pod returns its own pod name and namespace.
frontend pods are always contacting the backend through the backend
service. This results in a different backend pod servicing each Try running the `curl` command a few times, and notice what
request as well. changes. Ex: `watch -n 1 curl -s <ip>` Firstly, the frontend service
is directing your request to different frontend pods each time. The
## Cleanup frontend pods are always contacting the backend through the backend
service. This results in a different backend pod servicing each
```shell request as well.
kubectl delete rc,service -l type=show-type
kubectl delete rc,service -l type=backend-type ## Cleanup
```
```shell
kubectl delete rc,service -l type=show-type
kubectl delete rc,service -l type=backend-type
```