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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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Java memeory model


The java memory model has multiple areas to do different jobs, this model is in user space because it has no I/O control.


There are these parts:

  • Program counter register:
    • For java multi-thread switching different threads, and same functionality as OS counters.
    • (PC) Registers are created every time a new thread is created. The PC holds a pointer to the current statement being executed in its thread. If the currently executing method is 'native', then the value of the program counter register will be undefined.
  • Stack:
    • Private for each thread.
    • It contains method-specific primitive values and references to objects referenced from methods in the heap.
    • Whenever we call a new method, a new block is created on top of the stack which contains values specific to that method
  • Native Method stacks:
    • JVM that supports native methods will have native method stacks. It is used for native methods, and created per thread. 
  • Heap:
    • Heap data area is used to store objects of classes and arrays. 
    • Heap memory is common and shared across multiple threads. 
    • This is where the garbage collector comes into picture.
  • Method area:
    • Method area is created at JVM startup and shared among all the threads.
    • Method area has per class structures and fields. Nothing but static fields and structures.
    • Runtime constant pool is part of method area.

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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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Garbage Collectors

Table of contents [ hide ] The JVM ships with various options for garbage collection to support a variety of deployment options. With this, we get flexibility in choosing which garbage collector to use for our application. Serial GC The Serial collector uses a single thread for garbage collection. The serial collector is not even that powerful compared to other GCs but is useful in a uniprocessor or hardware-constrained environments. ParNew  GC  The parallel version of the Serial collector, before the emergence of G1 GC, the combination of ParNew and CMS worked together, and ParNew was responsible for the garbage collection of the new generation. Parallel Scavenge  GC  Aa a young generation GC, compare to other GCs, focuses on the throughput, and another important feature is the auto adjustment strategy to find the best throughput and pause time. Serial Old GC Serial Old GC is for the old-generation version of Serial GC. It has two purposes, one is to work with...
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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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