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(Re)Starting my journey into Kubernetes.
I enjoy building things and exploring new technologies. While I'm not an expert in everything, I'm a fast and practical learner. I specialize in programming with Go (Golang). Additionally, I work as a freelancer on Upwork. If you require assistance or have a job vacancy, feel free to reach out to me.
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It's time! I'm building a homelab, but in the cloud.
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Disclaimer: The information provided in this series may not be 100% accurate and may be unstructured. This is not a tutorial series; it is meant to document my learnings. If you happen to be interested in reading about my journey, stick around.
I haven't touched Kubernetes in about two years now (at the time of writing this blog). The last version of Kubernetes I used was v1.25. I started learning Kubernetes in mid-2022 when the startup I was working for decided to switch to it. It felt shiny and exciting, similar to how I felt when I first started using Linux. However, I lost touch with Kubernetes after I quit my internship and began freelancing. None of my clients had any Kubernetes requirements, and since I wasn't using Kubernetes for hosting my personal projects (because EKS is expensive and my workloads don't need to run on Kubernetes), I drifted away from it.
There are two reasons:
A Kubernetes engineer? Or should I say a Kubernetes developer/admin or maybe a DevOps engineer? Or for a more sophisticated title, perhaps an SRE? All these cloud-native jobs may have isolated roles and responsibilities on paper. However, in practice, the have a lot of overlap.
Episode 0 is mainly about writing down whatever I know about Kubernetes from memory. Some of the details might be incorrect or contain discrepancies. I also love creating visual sketches using Excalidraw, so I'll be sketching out representations whenever needed or possible.
kubelet and
kube-proxy, as well as a container runtime.containerd, which originated
from the Docker project when the Docker team decided to separate the
runtime from the Docker tool.CRI-O two years ago when I was
deploying a Kubernetes cluster on my Raspberry Pis using an official
tool called kubeadm.I know very little about this. All I remember is that it is used to load balance traffic across nodes.
Kubelet.
The Kubelet is then responsible for conveying these instructions to
the container runtime.Kubelet monitors the status of the node and
containers and communicates this information back to the API server.scheduler (part of the control-plane) schedules pods to these
nodes.nodeAffinity.kubelet, kube-proxy, and the container runtime,
the control-plane also houses the scheduler, controller manager,
and a key-value distributed database called Etcd.deployments, statefulsets, and replicasets. These controllers
watch for changes to their respective manifests using Etcd's
watching ability.kubelet via the API
server to converge to the desired state.
Credits: @antweiss on X
Endpoints object. I don't
remember much about the Endpoint object beyond its name.ClusterIP.Init containers initialize/prepare the environment for the main application container, which runs only after the init container exits with an exit code of 0.
kube-system
namespace.kubectl get pods -n kube-system
Could MetalLB not be used for a high-availability cluster to load balance traffic to the control-plane nodes ??
That's all I could recall off the top of my head. For now, I want to focus on reaffirming my Kubernetes knowledge and filling in the gaps. See you in the next episode.
I have templates stored for all the Kubernetes objects. I don't remember where I got them from, but they were quite handy.
kind: ConfigMap
apiVersion: v1
metadata:
name: ${1:myconfig}
namespace: ${2:default}
data:
${3:key}: ${4:value}
---
apiVersion: v1
kind: Secret
metadata:
name: ${1:mysecret}
namespace: ${2:default}
type: ${Opaque|kubernetes.io/service-account-token|kubernetes.io/dockercfg|kubernetes.io/dockerconfigjson|kubernetes.io/basic-auth|kubernetes.io/ssh-auth|kubernetes.io/tls}
# stringData:
# foo: bar
data:
# Example:
# password: {{ .Values.password | b64enc }}
---
apiVersion: v1
kind: PersistentVolume
metadata:
name: ${1:pvapp}
spec:
capacity:
storage: 1Gi
volumeMode: ${2:Filesystem|Block}
accessModes:
- ReadWriteOnce # RWO
- ReadOnlyMany # ROX
- ReadWriteMany # RWX
- ReadWriteOncePod # RWOP
persistentVolumeReclaimPolicy: ${3:Recycle|Retain|Delete}
storageClassName: default
nfs:
server: 172.17.0.2
path: /tmp
# hostPath:
# path: /path/to/directory
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
name: ${1:myapp}
namespace: ${2:default}
labels:
app: ${1:myapp}
spec:
# AKS: default,managed-premium
# GKE: standard
# EKS: gp2 (custom)
# Rook: rook-ceph-block,rook-ceph-fs
storageClassName: ${3|default,managed-premium,standard,gp2,rook-ceph-block,rook-ceph-fs|}
accessModes:
- ${4|ReadWriteOnce,ReadWriteMany,ReadOnlyMany|}
resources:
requests:
storage: ${5:2Gi}
---
# https://kubernetes.io/docs/concepts/storage/storage-classes
apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
name: ${1:standard}
provisioner: ${2:kubernetes.io/aws-ebs|kubernetes.io/azure-disk|kubernetes.io/gce-pd}
parameters:
type: gp2
reclaimPolicy: Retain
allowVolumeExpansion: true
mountOptions:
- debug
volumeBindingMode: Immediate
apiVersion: apps/v1
kind: Deployment
metadata:
name: ${1:myjob}
namespace: ${2:default}
labels:
app: ${1:myjob}
spec:
selector:
matchLabels:
app: ${1:myjob}
replicas: 1
strategy:
rollingUpdate:
maxSurge: 25%
maxUnavailable: 25%
type: RollingUpdate
template:
metadata:
labels:
app: ${1:myjob}
spec:
containers:
- name: ${1:myjob}
image: ${3:myjob:latest}
imagePullPolicy: ${4|IfNotPresent,Always,Never|}
resources:
requests:
cpu: 100m
memory: 100Mi
limits:
cpu: 100m
memory: 100Mi
livenessProbe:
tcpSocket:
port: ${5:80}
initialDelaySeconds: 5
timeoutSeconds: 5
successThreshold: 1
failureThreshold: 3
periodSeconds: 10
readinessProbe:
httpGet:
path: /_status/healthz
port: ${5:80}
initialDelaySeconds: 5
timeoutSeconds: 2
successThreshold: 1
failureThreshold: 3
periodSeconds: 10
env:
- name: DB_HOST
valueFrom:
configMapKeyRef:
name: ${1:myjob}
key: DB_HOST
# optional: true
# envFrom:
# prefix: CONFIG_
# - configMapRef:
# name: myconfig
# optional: true
ports:
- containerPort: ${5:80}
name: ${1:myjob}
volumeMounts:
- name: localtime
mountPath: /etc/localtime
volumes:
- name: localtime
persistentVolumeClaim:
claimName: myclaim
restartPolicy: Always
---
apiVersion: v1
kind: Service
metadata:
name: ${1:myjob}
namespace: ${2:default}
spec:
selector:
app: ${1:myjob}
type: ${3|ClusterIP,NodePort,LoadBalancer|ExternalName|}
ports:
- name: ${1:myjob}
protocol: ${4|TCP,UDP|}
port: ${5:80}
targetPort: ${6:5000}
nodePort: ${7:30001}
---
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
name: ${3:tls-example-ingress}
namespace: ${2:default}
spec:
tls:
- hosts:
- ${4:https-example.foo.com}
secretName: ${1:testsecret-tls}
rules:
- host: ${4:https-example.foo.com}
http:
paths:
- path: /${5}
pathType: Prefix
backend:
service:
name: ${6:service1}
port:
number: ${7:80}
---
apiVersion: apps/v1
kind: StatefulSet
metadata:
name: ${1:myapp}
namespace: ${2:default}
spec:
selector:
matchLabels:
app: ${1:myapp} # has to match .spec.template.metadata.labels
serviceName: ${1:myapp}
replicas: ${3:3} # by default is 1
template:
metadata:
labels:
app: ${1:myapp} # has to match .spec.selector.matchLabels
spec:
terminationGracePeriodSeconds: 10
containers:
- name: ${1:myapp}
image: ${4:${1:myapp}-slim:1.16.1}
ports:
- containerPort: ${5:80}
name: ${1:myapp}
volumeMounts:
- name: ${6:www}
mountPath: /usr/share/nginx/html
volumeClaimTemplates:
- metadata:
name: ${6:www}
spec:
storageClassName: ${7:my-storage-class}
accessModes:
- ${8|ReadWriteOnce,ReadWriteMany,ReadOnlyMany|}
resources:
requests:
storage: ${9:1Gi}
---
apiVersion: batch/v1
kind: Job
metadata:
name: ${1:myjob}
namespace: ${2:default}
labels:
app: ${1:myjob}
spec:
template:
metadata:
name: ${1:myjob}
labels:
app: ${1:myjob}
spec:
containers:
- name: ${1:myjob}
image: ${3:python:3.7.6-alpine3.10}
command: ['sh', '-c', '${4:python3 manage.py makemigrations && python3 manage.py migrate}']
env:
- name: ENV_NAME
value: ENV_VALUE
volumeMounts:
- name: localtime
mountPath: /etc/localtime
volumes:
- name: localtime
hostPath:
path: /usr/share/zoneinfo/Asia/Taipei
restartPolicy: OnFailure
dnsPolicy: ClusterFirst
---
apiVersion: batch/v1
kind: CronJob
metadata:
name: ${1:cronjobname}
namespace: ${2:default}
spec:
schedule: ${3:*/1 * * * *}
jobTemplate:
spec:
template:
spec:
containers:
- name: ${4:jobname}
image: ${5:busybox}
args: ['/bin/sh', '-c', '${6:date; echo Hello from the Kubernetes cluster}']
restartPolicy: OnFailure
---