Go Study Notes - Review of Go Fundamentals

2023-03-17

I. Basic Knowledge

1. Basic Data Types

Value Types:

bool (1 byte)
byte (1 byte, alias of uint8)
rune (4 bytes, alias of int32, range -2^31 to 2^31)
int (32 or 64 bits, 4 or 8 bytes)
int8 (1 byte), int16 (2 bytes), int32 (4 bytes), int64 (8 bytes)
uint (32 or 64 bits, 4 or 8 bytes)
uint8 (1 byte), uint16 (2 bytes), uint32 (4 bytes), uint64 (8 bytes)
float32 (4 bytes), float64 (8 bytes)
string     // Sequence of fixed-length characters, underlying is a byte array
complex64, complex128 (default) // Complex number type
array   // Array (fixed length)
struct  // Structure

Reference Types (Pointer Types):

1
2
3

slice  // Slice, default value is nil
map    // Map, default value is nil
chan   // Channel, default value is nil

2. Encoding & Strings

Go’s default encoding is UTF-8.

Deploying Jenkins in a Kubernetes Environment

wanzi

2023-03-16

1. Install and Deploy Jenkins

1. Manual Installation

Manual installation is straightforward—just prepare the YAML configuration in advance. The complete CICD resource file jenkins-install.yaml is as follows:

apiVersion: v1
kind: PersistentVolume
metadata:
  name: jenkins-pv
spec:
  storageClassName: local # Local PV
  capacity:
    storage: 30Gi
  volumeMode: Filesystem
  accessModes:
    - ReadWriteOnce
  local:
    path: /opt/jenkins
  nodeAffinity:
    required:
      nodeSelectorTerms:
        - matchExpressions:
            - key: kubernetes.io/hostname
              operator: In
              values:
                - node02
---
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: jenkins-pvc
  namespace: kube-ops
spec:
  storageClassName: local
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 30Gi
---
apiVersion: v1
kind: ServiceAccount
metadata:
  name: jenkins
  namespace: kube-ops
---
kind: ClusterRole
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: jenkins
rules:
  - apiGroups: ["extensions", "apps"]
    resources: ["deployments", "ingresses"]
    verbs: ["create", "delete", "get", "list", "watch", "patch", "update"]
  - apiGroups: [""]
    resources: ["services"]
    verbs: ["create", "delete", "get", "list", "watch", "patch", "update"]
  - apiGroups: [""]
    resources: ["pods"]
    verbs: ["create", "delete", "get", "list", "patch", "update", "watch"]
  - apiGroups: [""]
    resources: ["pods/exec"]
    verbs: ["create", "delete", "get", "list", "patch", "update", "watch"]
  - apiGroups: [""]
    resources: ["pods/log", "events"]
    verbs: ["get", "list", "watch"]
  - apiGroups: [""]
    resources: ["secrets"]
    verbs: ["get"]
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
  name: jenkins
  namespace: kube-ops
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: jenkins
subjects:
  - kind: ServiceAccount
    name: jenkins
    namespace: kube-ops
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: jenkins
  namespace: kube-ops
spec:
  selector:
    matchLabels:
      app: jenkins
  template:
    metadata:
      labels:
        app: jenkins
    spec:
      serviceAccount: jenkins
      initContainers:
        - name: fix-permissions
          image: busybox
          command: ["sh", "-c", "chown -R 1000:1000 /var/jenkins_home"]
          securityContext:
            privileged: true
          volumeMounts:
            - name: jenkinshome
              mountPath: /var/jenkins_home
      containers:
        - name: jenkins
          #image: jenkins/jenkins:lts
          image: jenkins/jenkins:2.375.3-lts # Use latest stable version
          imagePullPolicy: IfNotPresent
          env:
          - name: JAVA_OPTS
            value: -Dhudson.model.DownloadService.noSignatureCheck=true
          ports:
            - containerPort: 8080
              name: web
              protocol: TCP
            - containerPort: 50000
              name: agent
              protocol: TCP
          resources:
            limits:
              cpu: 1500m
              memory: 4096Mi
            requests:
              cpu: 1500m
              memory: 2048Mi
          readinessProbe:
            httpGet:
              path: /login
              port: 8080
            initialDelaySeconds: 60
            timeoutSeconds: 5
            failureThreshold: 12
          volumeMounts:
            - name: jenkinshome
              mountPath: /var/jenkins_home
      volumes:
        - name: jenkinshome
          persistentVolumeClaim:
            claimName: jenkins-pvc
---
apiVersion: v1
kind: Service
metadata:
  name: jenkins
  namespace: kube-ops
  labels:
    app: jenkins
spec:
  selector:
    app: jenkins
  ports:
    - name: web
      port: 8080
      targetPort: web
    - name: agent
      port: 50000
      targetPort: agent
---
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: jenkins
  namespace: kube-ops
spec:
  ingressClassName: traefik
  rules:
  - host: jenkins.test.com
    http:
      paths:
      - path: /
        pathType: Prefix
        backend:
          service:
            name: jenkins
            port:
              number: 8080

Apply the Jenkins installation:

Delve Version Too Low to Work with GoLand

wanzi

2023-03-15

Problem

While debugging code in GoLand recently, I kept encountering the following error:

`1`	`WARNING: undefined behavior - version of Delve is too old for Go version 1.19.3 (maximum supported version 1.18)`

Solution

The issue essentially means that the installed version of Delve is too old and incompatible with the current Go version.

To resolve this, update Delve. Since I’m using brew for installation, and the official documentation doesn’t provide detailed instructions for brew, we’ll install it directly.

Automatically Renew Free SSL Certificates for Your Blog

wanzi

2022-11-12

Background

If you run a website or personal blog, you need to keep track of your SSL certificate expiration every year. Recently, the SSL certificate for wnote.com is also approaching its expiry.

Obtaining an SSL certificate enables HTTPS access for your site. There are both free and paid options available. Major domestic cloud providers like Alibaba Cloud, Tencent Cloud, and UCloud offer free SSL certificate services, typically valid for one year and requiring manual renewal. If your audience is primarily overseas, consider using Cloudflare’s CDN with built-in free SSL protection.

A Recommended Markdown Tool for Writing Books — Possibly a GitBook Alternative

wanzi

2022-10-06

Introduction to mdBook

mdBook is a command-line tool written in Rust for creating books using Markdown. It’s ideal for crafting product or API documentation, tutorials, course materials, or any content requiring a clean, navigable, and customizable presentation. Functionally similar to GitBook, its greatest advantage lies in speed.

Lightweight, Markdown-based syntax
Built-in search functionality
Syntax highlighting
Multiple themes for customizing output appearance
Preprocessors support — extend markdown rendering by modifying content before processing
Backend support for multiple output formats
Speed — built with Rust, performance is excellent
Even supports automated testing of Rust code

Installing mdBook

Since mdBook is developed in Rust, you need to install Rust first.

Some summaries and reflections on CDN construction

wanzi

2022-09-07

The ongoing COVID-19 pandemic has repeatedly disrupted daily life and work. Over the past half year, I’ve experienced a lot—family members fell seriously ill, my grandmother passed away, and there were numerous personal matters to handle, which led me to pause blogging for six months.

Amid economic downturns, many industries have begun layoffs and business scaling back. Taking advantage of recent free time, I’m summarizing my past experience with CDN services.

Resolve Nginx file upload limits and 504 gateway timeout in Kubernetes

wanzi

2021-11-08

Recently, two recurring issues have arisen in our business operations using the Kubernetes cluster. Here’s a record of the solutions:

Frontend page file upload limited to 1M
POST requests from frontend to backend timing out with a 504 error

Solution for the first issue:
By default, Nginx limits upload size to 1M. To resolve this, add the following configuration in the http, server, or location blocks of the Nginx config:

Alibaba Cloud ACK supports both public and internal SLB.

wanzi

2021-10-21

I. Background

You have an ACK cluster.
Nginx Ingress Controller has been successfully deployed and bound to a public-facing SLB.

Note: Kubernetes clusters created via the Alibaba Cloud Container Service console automatically deploy an Nginx Ingress Controller during initialization, which is default-mounted to a public SLB instance.

II. Configuration

1. Create an Internal SLB

In the Alibaba Cloud console, create an internal SLB and bind it to your VPC.

2. Configure Nginx Ingress Controller

# my-nginx-ingress-slb-intranet.yaml
# intranet nginx ingress slb service
apiVersion: v1
kind: Service
metadata:
  # Name the service as nginx-ingress-lb-intranet.
  name: nginx-ingress-lb-intranet
  namespace: kube-system
  labels:
    app: nginx-ingress-lb-intranet
  annotations:
    # Specify the SLB instance type as internal.
    service.beta.kubernetes.io/alicloud-loadbalancer-address-type: intranet
    # Replace with your internal SLB instance ID.
    service.beta.kubernetes.io/alicloud-loadbalancer-id: <YOUR_INTRANET_SLB_ID>
    # Whether to automatically create SLB port listeners (overrides existing ones); can also be configured manually.
    #service.beta.kubernetes.io/alicloud-loadbalancer-force-override-listeners: 'false'
spec:
  type: LoadBalancer
  # Route traffic to other nodes
  externalTrafficPolicy: "Cluster"
  ports:
  - port: 80
    name: http
    targetPort: 80
  - port: 443
    name: https
    targetPort: 443
  selector:
    # Select pods with app=ingress-nginx
    app: ingress-nginx

Apply the service resource: