In Kubernetes, a service has following purposes/advantages.
- Expose Application to outside world.
- Service Discovery: Labels and Selectors.
- LoadBalancer or NodePort Mode.
- Install Kubeshark
Pre-requisites:
- Create deploy.yml file
- Create service.yml file
- Deploy deploy.yml
- Deploy service.yml
1. Expose Application to outside world
- a) Create deploy.yml file as below.
apiVersion: apps/v1
kind: Deployment
metadata:
name: sample-python-deployment
labels:
app: sample-python-app
spec:
replicas: 2
selector:
matchLabels:
app: sample-python-app
template:
metadata:
labels:
app: sample-python-app
spec:
containers:
- name: python-app
image: jasper475/d37-k8s-services-py-django-app:v2
ports:
- containerPort: 8000
- b) Create service.yml file as below.
apiVersion: v1
kind: Service
metadata:
name: sample-python-service
spec:
type: NodePort
selector:
app: sample-python-app
ports:
- port: 80
targetPort: 8000
nodePort: 30007
- c) Deploy deploy.yml file as below.
kubectl apply -f deploy.yaml
$ kubectl apply -f deploy.yaml
deployment.apps/sample-python-deployment created
- d) Deploy service.yml file as below.
kubectl apply -f service.yaml
$ kubectl apply -f deploy.yaml
service/sample-python-service configured
- e) NodePort service Type: service deployed as NodePort type
kubectl get svc
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 11d
sample-python-service NodePort 10.103.136.137 <none> 80:30007/TCP 2s
- f) Notice IP Address of Pod: Notice IP below
$ kubectl get pods -o wide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
sample-python-deployment-5787bd6b9f-656fn 1/1 Running 0 3h54m 10.244.0.35 minikube <none> <none>
sample-python-deployment-5787bd6b9f-t9ttj 1/1 Running 0 3h50m 10.244.0.36 minikube <none> <none>
- g) Access Application via IP Addr:Port: Note, Python application is exposed via Port 8000
$ minikube ssh
curl -L http://10.244.0.35:8000/demo ####Access via Pod IP Address *** It works ***
2. Service Discovery: Labels and Selectors.
- Edit 'service.yml' file
FROM:
spec:
type: NodePort
selector:
app: sample-python-app***
ports:
- port: 80
TO
spec:
type: NodePort
selector:
app: sample-python-a***
ports:
- port: 80
3. LoadBalancer or NodePort Mode.
- a) get svc: kubectl get svc
$ kubectl get svc
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 11d
sample-python-service NodePort 10.103.136.137 <none> 80:30007/TCP 33m
- b) SVC Type: NodePort
kubectl get svc
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 11d
sample-python-service NodePort 10.103.136.137 <none> 80:30007/TCP 2s
- c) Access SVC: via NodePort Mode
minikube ssh
$ pwd
/home/docker
$ curl -L http://10.103.136.137:8000/demo ####Access via Cluster IP of svc on port 8000 - ******* Doesn't work*********
curl: (28) Failed to connect to 10.103.136.137 port 8000 after 131079 ms: Connection timed out
$ curl -L http://10.103.136.137:80/demo ####Access via Cluster IP of svc on port 80 - ******* Hurray, it works !!! *********
$ curl -L http://10.103.136.137:8000/demo ####Access via Pod IP Address
_ _
_ _ ( ) ( )
___ ___ (_) ___ (_)| |/') _ _ | |_ __
/' _ ` _ `\| |/' _ `\| || , < ( ) ( )| '_`\ /'__`\
| ( ) ( ) || || ( ) || || |\`\ | (_) || |_) )( ___/
(_) (_) (_)(_)(_) (_)(_)(_) (_)`\___/'(_,__/'`\____)
$ curl -L http://10.103.136.137:80
<!DOCTYPE html>
<html lang="en">
<head>
<meta http-equiv="content-type" content="text/html; charset=utf-8">
<title>Page not found at /</title>
<meta name="robots" content="NONE,NOARCHIVE">
<style type="text/css">
html * { padding:0; margin:0; }
body * { padding:10px 20px; }
body * * { padding:0; }
body { font:small sans-serif; background:#eee; color:#000; }
body>div { border-bottom:1px solid #ddd; }
h1 { font-weight:normal; margin-bottom:.4em; }
h1 span { font-size:60%; color:#666; font-weight:normal; }
table { border:none; border-collapse: collapse; width:100%; }
td, th { vertical-align:top; padding:2px 3px; }
th { width:12em; text-align:right; color:#666; padding-right:.5em; }
#info { background:#f6f6f6; }
#info ol { margin: 0.5em 4em; }
#info ol li { font-family: monospace; }
#summary { background: #ffc; }
#explanation { background:#eee; border-bottom: 0px none; }
pre.exception_value { font-family: sans-serif; color: #575757; font-size: 1.5em; margin: 10px 0 10px 0; }
</style>
</head>
<body>
<div id="summary">
<h1>Page not found <span>(404)</span></h1>
<table class="meta">
<tr>
<th>Request Method:</th>
<td>GET</td>
</tr>
<tr>
<th>Request URL:</th>
<td>http://10.103.136.137/</td>
- d) Edit svc: kubectl edit svc service-name
$ kubectl edit svc sample-python-service
-------------------------------------------------------------------
# Please edit the object below. Lines beginning with a '#' will be ignored,
# and an empty file will abort the edit. If an error occurs while saving this file will be
# reopened with the relevant failures.
#
apiVersion: v1
kind: Service
metadata:
annotations:
kubectl.kubernetes.io/last-applied-configuration: |
{"apiVersion":"v1","kind":"Service","metadata":{"annotations":{},"name":"sample-python-service","namespace":"default"},"spec":{"ports":[{"nodePort":30007,"port":80,"targetPort":8000}],"selector":{"app":"sample-python-app"},"type":"NodePort"}}
creationTimestamp: "2024-01-11T02:51:02Z"
name: sample-python-service
namespace: default
resourceVersion: "16469"
uid: bd9bd510-e633-4dc1-adc1-1cc4704378d3
spec:
allocateLoadBalancerNodePorts: true
clusterIP: 10.103.136.137
clusterIPs:
- 10.103.136.137
externalTrafficPolicy: Cluster
internalTrafficPolicy: Cluster
ipFamilies:
- IPv4
ipFamilyPolicy: SingleStack
ports:
- nodePort: 30007
port: 80
protocol: TCP
targetPort: 8000
selector:
app: sample-python-app
sessionAffinity: None
type: ***LoadBalancer***
status:
loadBalancer: {}
-------------------------------------------------------------------
service/sample-python-service edited
SVC Type: LoadBalancer - notice
EXTERNAL-IPis<pending>state. Because, in Minikube this won't be creating an IP address whereas, in any cloud providers such as AWS EC2 or Azure VM or GCP Engine -EXTERNAL-IPwill be assigned viaCloud-Control Manager
kubectl get svc
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 11d
sample-python-service LoadBalancer 10.103.136.137 <pending> 80:30007/TCP 34m
Get `Minikube ip'
$ minikube ip
192.168.59.105
Access via browser http://192.168.59.105:30007/demo
or curl -L http://192.168.59.105:30007/demo
4. Install Kubeshark
- a) Install Kubeshark as below
git clone: git clone https://github.com/kubeshark/kubeshark
PS C:\Users\Jasper> git clone https://github.com/kubeshark/kubeshark
Cloning into 'kubeshark'...
remote: Enumerating objects: 20781, done.
remote: Counting objects: 100% (1668/1668), done.
remote: Compressing objects: 100% (262/262), done.
remote: Total 20781 (delta 1525), reused 1491 (delta 1406), pack-reused 19113
Receiving objects: 100% (20781/20781), 26.38 MiB | 19.53 MiB/s, done.
Resolving deltas: 100% (14618/14618), done.
PS C:\Users\Jasper>
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