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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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GC Basic Algorithm

Theory Most GCs follow the theory of generational collection, which is based on the following two: Week generational hypothesis:  Most of the objects are short-living. Strong generational hypothesis:  The more times an object survives GC, the harder it is to die. Mark-Sweep After the marking phase has been completed all space occupied by unvisited objects is considered free and can thus be reused to allocate new objects. There may exist plenty of free regions but if no single region is large enough to accommodate the allocation, the allocation is still going to fail. Mark-Copy To avoid excessive fragmentation, it splits the space into two parts and copies the surviving objects into empty parts. The disadvantage is the need for one more memory region, which should be large enough to accommodate survived objects. Mark-Compact Like mark-copy, it doesn't require another space to copy but a more complex operation to move the object. Reachability analysis First, GC defines some spe...
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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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Thread and concurrency

Table of contents [ hide ] Thread Thread is a lightweight process, a basic unit of CPU utilization. All threads belonging to the same process share: Code section. Data section. OS resources(e.g. open files and signals) Each thread has its own(thread control block): Thread ID. Program counter. Register set. A tack. Benefits of multithreading: Responsiveness. Resource sharing. Utilization of NP arch. Economy. User vs Kernel threads User threads Thread management is done by the user-level thread library. POSIX Pthreads. Win32 threads. Java threads. Thread library provides support for thread creation, scheduling, and deletion. Generally fast to create and manage. If the kernel is single-threaded, a user-thread block -> entire process blocks even if other threads are ready to run. Kernel threads Supported by the kernel(OS) directly. Windows 2000(NT) Solaris Linux Tr64 UNIX The kernel performs thread creation, scheduling, etc. Generally slower to create and manage. If a thread is blo...
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