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Install K8S on VM and spring boot integration.

Installation Environment Vmware Workstation pro  It is recommended to use the  snapshot  to store the state of each installation stage to avoid installation failures and causing the installation to start from scratch. Ubuntu 22.04 windows 11 Hardware settings  create 3 VM: 4 cores and 4G memory and 100G capacity Before installing K8s (All use the root user) set host: 192.168.47.135 master 192.168.47.131 node1 192.168.47.132 node2 set root ssh connection: sudo su - echo "PermitRootLogin yes" >> /etc/ssh/sshd_config systemctl restart sshd sudo passwd ssh-keygen for i in {master,node1,node2}; do  ssh-copy-id root@$i; done set Ipvs and conf  create conf file: for i in {master,node1,node2}; do ssh root@$i 'cat << EOF > /etc/modules-load.d/containerd.conf overlay br_netfilter EOF'; done execute conf: for i in {master,node1,node2}; do ssh root@$i 'modprobe overlay;modprobe br_netfilter;'; done create 99-kubernetes-cri.conf file: for i in {maste...
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Composition and Inheritance


Composition vs Inheritance

In "Effective JAVA" or if you search the Internet, you will find that everyone says that composition is better than inheritance.

We know the composition has the advantages of the following:

  • Composition is loosely coupled.
  • The composition has better access control. 
  • Composition is more flexible.
  • Unit test easier.

Is this really true? usually yes, but let's back to thinking about it, what are we programmed for, methods are just tools, and people are the core.

Let's see what the advantage is of inheritance before we choose the methods. here.

Choosing the best fit method for the program is the most important thing, not just avoiding inheritance.


reference:

https://www.digitalocean.com/community/tutorials/composition-vs-inheritance

https://github.com/hollischuang/toBeTopJavaer


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OS basic

Table of contents [ hide ] OS architecture The operating system architecture consists of three parts, user mode, kernel mode, and hardware. User mode is for the application to execute the user's program. Kernel mode is to control all the I/O devices and system stability. Storage device hierarchy System call The system call is a kind of software interrupt, including six categories. Process control. File management. Device management. Information maintenance. Communication. Protection. System calls use three methods to pass parameters. Registers. The table in memory. Push onto the stack. A view of operating system services reference: https://www.amazon.com/-/zh_TW/Operating-System-Concepts-Abraham-Silberschatz/dp/1119800366/ref=sr_1_1?keywords=Operating-System-Concepts&qid=1669538704&s=books&sr=1-1
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JVM Tools

Table of contents [ hide ]  Java has many useful tools for debugging at runtime or analyzing an application after it has crashed. Commands jps - JVM process Status Tool Same as the Linux command ps, only to find the process under the JVM. jinfo - Configuration Info for Java Show and adjust the JVM arguments. jmap - Memory Map for Java Getting a memory error dump is the most common technique used at runtime. The dump file can be used to analyze the cause of the failure. jstack - Stack trace for Java Check the thread runtime status. GUI VisualVM VisualVM is a tool that provides a visual interface for viewing detailed information about Java applications while they are running on a Java Virtual Machine (JVM). Memory Analyzer (MAT) The Eclipse Memory Analyzer is a fast and feature-rich Java heap analyzer that helps you find memory leaks and reduce memory consumption. reference: https://www.amazon.com/depth-understanding-Java-Virtual-Machine/dp/7111641248 https://en.wikipedia.org/w...
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