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CH04_L04

README.md

Services Expanded Lab

Objectives

  1. Explore Headless,External and Cluster IP Services

Prereq

  1. Running kind cluster

Setup Steps

  1. Deploy Kind Cluster
  2. Deploy DNS utils images
  3. Deploy Services
  4. Explore Service Network

1. Deploy Kind Cluster

  1. Start kind cluster
kind create cluster --name service --config kind.yml
± |master {1} S:5 U:4 ?:1 ✗| → kind create cluster --config kind.config --name nodeport
Creating cluster "service" ...
 ✓ Ensuring node image (kindest/node:v1.16.3) 🖼
 ✓ Preparing nodes 📦
 ✓ Writing configuration 📜
 ✓ Starting control-plane 🕹️
 ✓ Installing CNI 🔌
 ✓ Installing StorageClass 💾
 ✓ Joining worker nodes 🚜
Set kubectl context to "kind-service"
You can now use your cluster with:

kubectl cluster-info --context kind-service

Have a nice day! 👋

2. Deploy DNS utils images

dnsutils is used for kubernetes end to end testing

kubectl apply -f dnsutils.yml

3. Deploy Services

You can deploy one by one or all together

kubectl apply -f service-headless.yml,service.yml,service-external.yml
service/headless-service unchanged
deployment.apps/app created
service/clusterip-service created
service/external-service created

ClusterIP Service

kubectl apply -f service.yml

Headless Service

kubectl apply -f service-headless.yml

External Service

kubectl apply -f external-headless.yml

Verify everything deploy successfully

Resolve Cluster IP service

 kubectl exec -it dnsutils -- host -v -t a clusterip-service
Trying "clusterip-service.default.svc.cluster.local"
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 62956
;; flags: qr aa rd; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;clusterip-service.default.svc.cluster.local. IN        A

;; ANSWER SECTION:
clusterip-service.default.svc.cluster.local. 30 IN A 10.102.42.19

Received 120 bytes from 10.96.0.10#53 in 0 ms

Resolve Headless service

kubectl exec -it dnsutils -- host -v -t a headless-service
Trying "headless-service.default.svc.cluster.local"
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 26926
;; flags: qr aa rd; QUERY: 1, ANSWER: 7, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;headless-service.default.svc.cluster.local. IN A

;; ANSWER SECTION:
headless-service.default.svc.cluster.local. 30 IN A 10.244.3.3
headless-service.default.svc.cluster.local. 30 IN A 10.244.1.2
headless-service.default.svc.cluster.local. 30 IN A 10.244.1.4
headless-service.default.svc.cluster.local. 30 IN A 10.244.2.3
headless-service.default.svc.cluster.local. 30 IN A 10.244.3.2
headless-service.default.svc.cluster.local. 30 IN A 10.244.2.2
headless-service.default.svc.cluster.local. 30 IN A 10.244.1.3

Received 466 bytes from 10.96.0.10#53 in 0 ms

Resolve External service

kubectl exec -it dnsutils -- host -v -t a external-service
Trying "external-service.default.svc.cluster.local"
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 17944
;; flags: qr aa rd; QUERY: 1, ANSWER: 2, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;external-service.default.svc.cluster.local. IN A

;; ANSWER SECTION:
external-service.default.svc.cluster.local. 30 IN CNAME google.com.
google.com.             30      IN      A       172.217.5.14

Received 152 bytes from 10.96.0.10#53 in 15 ms

4. Explore Services

Let's Debug one of the pods from the Service

kubectl get pods -l app=app1

Run Pod watcher in a separate terminal, you'll see the Deployment create a new pod since the label changed, which in turn will create a new Endpoint

kubectl get pods --watch
NAME                  READY   STATUS    RESTARTS   AGE
app-ff9cd5f65-76xhg   1/1     Running   0          7s
app-ff9cd5f65-d55vk   1/1     Running   0          7s
app-ff9cd5f65-hlfqd   1/1     Running   0          7s
app-ff9cd5f65-lcwks   1/1     Running   0          7s
app-ff9cd5f65-lvpkq   1/1     Running   0          7s
app-ff9cd5f65-p6rwq   1/1     Running   0          7sx`
app-ff9cd5f65-qh4qs   1/1     Running   0          7s
dnsutils              1/1     Running   0          14m
app-ff9cd5f65-76xhg   1/1     Running   0          36s
app-ff9cd5f65-76xhg   1/1     Running   0          36s
app-ff9cd5f65-phhfv   0/1     Pending   0          0s
app-ff9cd5f65-phhfv   0/1     Pending   0          0s
app-ff9cd5f65-phhfv   0/1     ContainerCreating   0          0s
app-ff9cd5f65-phhfv   1/1     Running             0          1s

Change the Label to remove the App from the Service and Endpoints

 kubectl label pod app-ff9cd5f65-2n77z app=debug --overwrite=true

You'll see 8 pods running now

kubectl get pods -o wide --show-labels
NAME                  READY   STATUS    RESTARTS   AGE     LABELS
app-ff9cd5f65-76xhg   1/1     Running   0          4m3s    app=debug,pod-template-hash=ff9cd5f65
app-ff9cd5f65-8wfr2   1/1     Running   0          10s     app=app1,pod-template-hash=ff9cd5f65
app-ff9cd5f65-d55vk   1/1     Running   0          4m3s    app=debug,pod-template-hash=ff9cd5f65
app-ff9cd5f65-hlfqd   1/1     Running   0          4m3s    app=app1,pod-template-hash=ff9cd5f65
app-ff9cd5f65-lcwks   1/1     Running   0          4m3s    app=app1,pod-template-hash=ff9cd5f65
app-ff9cd5f65-lvpkq   1/1     Running   0          4m3s    app=app1,pod-template-hash=ff9cd5f65
app-ff9cd5f65-p6rwq   1/1     Running   0          4m3s    app=app1,pod-template-hash=ff9cd5f65
app-ff9cd5f65-phhfv   1/1     Running   0          3m27s   app=app1,pod-template-hash=ff9cd5f65
app-ff9cd5f65-qh4qs   1/1     Running   0          4m3s    app=app1,pod-template-hash=ff9cd5f65
dnsutils              1/1     Running   0          18m     <none>

It will be removed from the Endpoints for the services

kubectl describe endpoints clusterip-service
   Name:         clusterip-service
   Namespace:    default
   Labels:       app=app1
   Annotations:  endpoints.kubernetes.io/last-change-trigger-time: 2020-04-25T20:02:12Z
   Subsets:
     Addresses:          10.244.1.2,10.244.1.3,10.244.2.2,10.244.2.3,10.244.2.4,10.244.3.2,10.244.3.3
     NotReadyAddresses:  <none>
     Ports:
       Name     Port  Protocol
       ----     ----  --------
       <unset>  8080  TCP
   
   Events:  <none>

Let's Explore the Effects of DNS resolutions on google.com using an External Service

 kubectl exec -it dnsutils -- host -v -t a google.com 8.8.8.8
 Trying "google.com.default.svc.cluster.local"
 Trying "google.com.svc.cluster.local"
 Trying "google.com.cluster.local"
 Trying "google.com"
 Using domain server:
 Name: 8.8.8.8
 Address: 8.8.8.8#53
 Aliases: 
 
 ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 40188
 ;; flags: qr rd ra; QUERY: 1, ANSWER: 6, AUTHORITY: 0, ADDITIONAL: 0
 
 ;; QUESTION SECTION:
 ;google.com.                    IN      A
 
 ;; ANSWER SECTION:
 google.com.             281     IN      A       64.233.185.139
 google.com.             281     IN      A       64.233.185.138
 google.com.             281     IN      A       64.233.185.101
 google.com.             281     IN      A       64.233.185.100
 google.com.             281     IN      A       64.233.185.113
 google.com.             281     IN      A       64.233.185.102
 
 Received 124 bytes from 8.8.8.8#53 in 15 ms
kubectl exec -it dnsutils -- host -v -t a google.com
Trying "google.com.default.svc.cluster.local"
Trying "google.com.svc.cluster.local"
Trying "google.com.cluster.local"
Trying "google.com"
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 11603
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;google.com.                    IN      A

;; ANSWER SECTION:
google.com.             30      IN      A       172.217.5.14

Received 54 bytes from 10.96.0.10#53 in 2 ms
kubectl exec -it dnsutils -- host -v -t a external-service
Trying "external-service.default.svc.cluster.local"
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 11610
;; flags: qr aa rd; QUERY: 1, ANSWER: 2, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;external-service.default.svc.cluster.local. IN A

;; ANSWER SECTION:
external-service.default.svc.cluster.local. 20 IN CNAME google.com.
google.com.             20      IN      A       172.217.5.14

Received 152 bytes from 10.96.0.10#53 in 0 ms