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Enhancements in clarity to access-application-cluster/connecting-frontend-backend.md (#25927)

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* Enhancements in clarity to docs/tasks/access-application-cluster/connecting-frontend-backend.md

* Code review comments

* Reverting name of service due to backed value in Dockerimage
This commit is contained in:
Leonardo Murillo
2021-01-13 19:47:03 -06:00
committed by GitHub
parent ee4af3155c
commit f7b29716fd
9 changed files with 114 additions and 93 deletions
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content/en/docs/tasks/access-application-cluster/connecting-frontend-backend.md
+51 -40
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@@ -1,22 +1,24 @@
---
title: Connect a Front End to a Back End Using a Service
title: Connect a Frontend to a Backend Using Services
content_type: tutorial
weight: 70
---
<!-- overview -->
This task shows how to create a frontend and a backend
microservice. The backend microservice is a hello greeter. The
frontend and backend are connected using a Kubernetes
{{< glossary_tooltip term_id="service" >}} object.
This task shows how to create a _frontend_ and a _backend_ microservice. The backend
microservice is a hello greeter. The frontend exposes the backend using nginx and a
Kubernetes {{< glossary_tooltip term_id="service" >}} object.
## {{% heading "objectives" %}}
* Create and run a microservice using a {{< glossary_tooltip term_id="deployment" >}} object.
* Route traffic to the backend using a frontend.
* Use a Service object to connect the frontend application to the
backend application.
* Create and run a sample `hello` backend microservice using a
{{< glossary_tooltip term_id="deployment" >}} object.
* Use a Service object to send traffic to the backend microservice's multiple replicas.
* Create and run a `nginx` frontend microservice, also using a Deployment object.
* Configure the frontend microservice to send traffic to the backend microservice.
* Use a Service object of `type=LoadBalancer` to expose the frontend microservice
outside the cluster.
## {{% heading "prerequisites" %}}
@@ -34,24 +36,24 @@ require a supported environment. If your environment does not support this, you
The backend is a simple hello greeter microservice. Here is the configuration
file for the backend Deployment:
{{< codenew file="service/access/hello.yaml" >}}
{{< codenew file="service/access/backend-deployment.yaml" >}}
Create the backend Deployment:
```shell
kubectl apply -f https://k8s.io/examples/service/access/hello.yaml
kubectl apply -f https://k8s.io/examples/service/access/backend-deployment.yaml
```
View information about the backend Deployment:
```shell
kubectl describe deployment hello
kubectl describe deployment backend
```
The output is similar to this:
```
Name: hello
Name: backend
Namespace: default
CreationTimestamp: Mon, 24 Oct 2016 14:21:02 -0700
Labels: app=hello
@@ -59,7 +61,7 @@ Labels: app=hello
track=stable
Annotations: deployment.kubernetes.io/revision=1
Selector: app=hello,tier=backend,track=stable
Replicas: 7 desired | 7 updated | 7 total | 7 available | 0 unavailable
Replicas: 3 desired | 3 updated | 3 total | 3 available | 0 unavailable
StrategyType: RollingUpdate
MinReadySeconds: 0
RollingUpdateStrategy: 1 max unavailable, 1 max surge
@@ -80,14 +82,14 @@ Conditions:
Available True MinimumReplicasAvailable
Progressing True NewReplicaSetAvailable
OldReplicaSets: <none>
NewReplicaSet: hello-3621623197 (7/7 replicas created)
NewReplicaSet: hello-3621623197 (3/3 replicas created)
Events:
...
```
## Creating the backend Service object
## Creating the `hello` Service object
The key to connecting a frontend to a backend is the backend
The key to sending requests from a frontend to a backend is the backend
Service. A Service creates a persistent IP address and DNS name entry
so that the backend microservice can always be reached. A Service uses
{{< glossary_tooltip text="selectors" term_id="selector" >}} to find
@@ -95,42 +97,51 @@ the Pods that it routes traffic to.
First, explore the Service configuration file:
{{< codenew file="service/access/hello-service.yaml" >}}
{{< codenew file="service/access/backend-service.yaml" >}}
In the configuration file, you can see that the Service routes traffic to Pods
that have the labels `app: hello` and `tier: backend`.
In the configuration file, you can see that the Service, named `hello` routes
traffic to Pods that have the labels `app: hello` and `tier: backend`.
Create the `hello` Service:
Create the backend Service:
```shell
kubectl apply -f https://k8s.io/examples/service/access/hello-service.yaml
kubectl apply -f https://k8s.io/examples/service/access/backend-service.yaml
```
At this point, you have a backend Deployment running, and you have a
Service that can route traffic to it.
At this point, you have a `backend` Deployment running three replicas of your `hello`
application, and you have a Service that can route traffic to them. However, this
service is neither available nor resolvable outside the cluster.
## Creating the frontend
Now that you have your backend, you can create a frontend that connects to the backend.
The frontend connects to the backend worker Pods by using the DNS name
given to the backend Service. The DNS name is "hello", which is the value
of the `name` field in the preceding Service configuration file.
Now that you have your backend running, you can create a frontend that is accessible
outside the cluster, and connects to the backend by proxying requests to it.
The Pods in the frontend Deployment run an nginx image that is configured
to find the hello backend Service. Here is the nginx configuration file:
The frontend sends requests to the backend worker Pods by using the DNS name
given to the backend Service. The DNS name is `hello`, which is the value
of the `name` field in the `examples/service/access/backend-service.yaml`
configuration file.
{{< codenew file="service/access/frontend.conf" >}}
The Pods in the frontend Deployment run a nginx image that is configured
to proxy requests to the `hello` backend Service. Here is the nginx configuration file:
Similar to the backend, the frontend has a Deployment and a Service. The
configuration for the Service has `type: LoadBalancer`, which means that
the Service uses the default load balancer of your cloud provider.
{{< codenew file="service/access/frontend-nginx.conf" >}}
{{< codenew file="service/access/frontend.yaml" >}}
Similar to the backend, the frontend has a Deployment and a Service. An important
difference to notice between the backend and frontend services, is that the
configuration for the frontend Service has `type: LoadBalancer`, which means that
the Service uses a load balancer provisioned by your cloud provider and will be
accessible from outside the cluster.
{{< codenew file="service/access/frontend-service.yaml" >}}
{{< codenew file="service/access/frontend-deployment.yaml" >}}
Create the frontend Deployment and Service:
```shell
kubectl apply -f https://k8s.io/examples/service/access/frontend.yaml
kubectl apply -f https://k8s.io/examples/service/access/frontend-deployment.yaml
kubectl apply -f https://k8s.io/examples/service/access/frontend-service.yaml
```
The output verifies that both resources were created:
@@ -178,7 +189,7 @@ cluster.
## Send traffic through the frontend
The frontend and backends are now connected. You can hit the endpoint
The frontend and backend are now connected. You can hit the endpoint
by using the curl command on the external IP of your frontend Service.
```shell
@@ -196,17 +207,17 @@ The output shows the message generated by the backend:
To delete the Services, enter this command:
```shell
kubectl delete services frontend hello
kubectl delete services frontend backend
```
To delete the Deployments, the ReplicaSets and the Pods that are running the backend and frontend applications, enter this command:
```shell
kubectl delete deployment frontend hello
kubectl delete deployment frontend backend
```
## {{% heading "whatsnext" %}}
* Learn more about [Services](/docs/concepts/services-networking/service/)
* Learn more about [ConfigMaps](/docs/tasks/configure-pod-container/configure-pod-configmap/)
* Learn more about [DNS for Service and Pods](/docs/concepts/services-networking/dns-pod-service/)
content/en/examples/service/access/Dockerfile
+1 -1
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@@ -1,4 +1,4 @@
FROM nginx:1.17.3
RUN rm /etc/nginx/conf.d/default.conf
COPY frontend.conf /etc/nginx/conf.d
COPY frontend-nginx.conf /etc/nginx/conf.d
content/en/examples/service/access/hello.yaml → content/en/examples/service/access/backend-deployment.yaml
+4 -2
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@@ -1,14 +1,15 @@
---
apiVersion: apps/v1
kind: Deployment
metadata:
name: hello
name: backend
spec:
selector:
matchLabels:
app: hello
tier: backend
track: stable
replicas: 7
replicas: 3
template:
metadata:
labels:
@@ -22,3 +23,4 @@ spec:
ports:
- name: http
containerPort: 80
...
content/en/examples/service/access/hello-service.yaml → content/en/examples/service/access/backend-service.yaml
+2
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@@ -1,3 +1,4 @@
---
apiVersion: v1
kind: Service
metadata:
@@ -10,3 +11,4 @@ spec:
- protocol: TCP
port: 80
targetPort: http
...
content/en/examples/service/access/frontend-deployment.yaml
+27
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@@ -0,0 +1,27 @@
---
apiVersion: apps/v1
kind: Deployment
metadata:
name: frontend
spec:
selector:
matchLabels:
app: hello
tier: frontend
track: stable
replicas: 1
template:
metadata:
labels:
app: hello
tier: frontend
track: stable
spec:
containers:
- name: nginx
image: "gcr.io/google-samples/hello-frontend:1.0"
lifecycle:
preStop:
exec:
command: ["/usr/sbin/nginx","-s","quit"]
...
content/en/examples/service/access/frontend-nginx.conf
+14
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@@ -0,0 +1,14 @@
# The identifier Backend is internal to nginx, and used to name this specific upstream
upstream Backend {
# hello is the internal DNS name used by the backend Service inside Kubernetes
server hello;
}
server {
listen 80;
location / {
# The following statement will proxy traffic to the upstream named Backend
proxy_pass http://Backend;
}
}
content/en/examples/service/access/frontend-service.yaml
+15
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@@ -0,0 +1,15 @@
---
apiVersion: v1
kind: Service
metadata:
name: frontend
spec:
selector:
app: hello
tier: frontend
ports:
- protocol: "TCP"
port: 80
targetPort: 80
type: LoadBalancer
...
content/en/examples/service/access/frontend.conf
-11
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@@ -1,11 +0,0 @@
upstream hello {
server hello;
}
server {
listen 80;
location / {
proxy_pass http://hello;
}
}
content/en/examples/service/access/frontend.yaml
-39
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@@ -1,39 +0,0 @@
apiVersion: v1
kind: Service
metadata:
name: frontend
spec:
selector:
app: hello
tier: frontend
ports:
- protocol: "TCP"
port: 80
targetPort: 80
type: LoadBalancer
---
apiVersion: apps/v1
kind: Deployment
metadata:
name: frontend
spec:
selector:
matchLabels:
app: hello
tier: frontend
track: stable
replicas: 1
template:
metadata:
labels:
app: hello
tier: frontend
track: stable
spec:
containers:
- name: nginx
image: "gcr.io/google-samples/hello-frontend:1.0"
lifecycle:
preStop:
exec:
command: ["/usr/sbin/nginx","-s","quit"]