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Teek Technical Notes

website·Indexed 32 days ago

https://notes.teek.top/

A comprehensive collection of technical notes covering Java and JVM internals (class loading, tuning, and diagnostics), Spring and Spring Boot (unit testing, parameter validation), Nginx (load balancing, reverse proxy, Lua modules), ActiveMQ (persistence and advanced features), Docker networking, Kubernetes resource scheduling, and behavioral design patterns.

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What's inside Teek Notes

  1. Overview of the JVM Execution Engine

    The Execution Engine is a core component of the JVM responsible for translating Java bytecode into native machine instructions that the host operating system can execute. It consists of three primary components: the Interpreter, the JIT (Just-In-Time) Compiler, and the Garbage Collector. Because the execution engine is implemented in software, it allows the JVM to define its own instruction set independently of the underlying physical hardware.

  2. Overview of implementing delay queues with RabbitMQ

    RabbitMQ can be used to implement delay queues for scenarios requiring deferred message processing. Using RabbitMQ for this purpose provides several advantages: reliable message sending and delivery, the use of Dead Letter Exchanges (DLX) to ensure messages are consumed at least once and not discarded if processing fails, and high availability through clustering to prevent single points of failure and message loss.

  3. Overview of Continuous Integration (CI) and Jenkins

    Continuous Integration (CI) is the practice of frequently integrating code into the main branch (multiple times a day) to enable rapid iteration while maintaining high quality. The core requirement is that code must pass automated tests before being integrated.

    Jenkins is a popular open-source CI tool used to automate the building, testing, and deployment phases of software development.

    Official Website: http://jenkins-ci.org/

  4. Overview of Java Language Design Goals

    Java was designed as a simplification and improvement over C and C++, aiming to eliminate the complexities of manual memory management and pointer manipulation. Its core design goals include:

    • Syntax: Similar to C for ease of adoption.
    • Memory Management: Automatic memory management to replace manual allocation/deallocation.
    • Safety: Removal of pointers to prevent out-of-bounds memory errors and ensure type safety.
    • Portability: "Write Once, Run Anywhere" (WORA) achieved via the Java Virtual Machine (JVM), which acts as an abstraction layer between the application and the operating system.
    • Paradigm: Fully object-oriented.
    • Standard Library: Provision of a high-quality class library bundled with the language.

  6. Overview of kube-prometheus monitoring solution

    kube-prometheus is a full-stack monitoring solution that uses the Prometheus Operator to manage Prometheus and Alertmanager via Custom Resource Definitions (CRDs). Key resources include:

    • Prometheus: Defines the deployment state of the Prometheus cluster.
    • ServiceMonitor: Describes the targets Prometheus should monitor based on services.
    • PodMonitor: Describes the targets Prometheus should monitor based on pods.

  7. Overview of the Proxy Design Pattern

    The Proxy Pattern provides a surrogate or placeholder for another object to control access to it. This allows for the addition of extra functionality (enhancements) to the target object without modifying its original code. It is particularly useful for handling remote objects, objects with high creation costs, or objects requiring security restrictions.

    Advantages:

    • Acts as an intermediary and protector for the target object.
    • Allows extension of target object functionality.
    • Decouples the client from the target object, increasing system extensibility.

    Disadvantages:

    • Increases the number of classes in the system.
    • May slow down request processing due to the additional proxy layer.
    • Increases overall system complexity.

  8. Overview of Redis Data Types

    Redis supports five primary data types:

    • String: The most basic type; binary-safe (can store images or serialized objects). Maximum value size is 512MB.
    • Hash: A collection of field-value pairs, similar to a Java Map. Ideal for storing objects.
    • List: A collection of strings sorted by insertion order. Implemented as a linked list; elements can be added to the head (left) or tail (right).
    • Set: An unordered collection of unique strings, implemented via a HashTable.
    • Zset (Sorted Set): A collection of unique strings where each element is associated with a double-precision floating-point score used for sorting.

  9. Overview of the Seven Design Pattern Principles

    Design pattern principles are the foundational guidelines programmers should follow to ensure software is maintainable and extensible. They serve as the rationale behind why specific design patterns are structured the way they are. The seven commonly used principles are:

    1. Single Responsibility Principle (SRP)
    2. Interface Segregation Principle (ISP)
    3. Dependency Inversion Principle (DIP)
    4. Liskov Substitution Principle (LSP)
    5. Open-Closed Principle (OCP)
    6. Demeter's Law (Law of Demeter)
    7. Composite Reuse Principle

  10. Overview of Java 12 New Features (JEPs)

    Java 12 (released March 2019) introduced several JDK Enhancement Proposals (JEPs) aimed at performance and language simplification:

    • JEP 325: Switch Expressions (Preview): Simplifies switch statements and allows them to be used as expressions.
    • JEP 189: Shenandoah GC (Experimental): A low-pause-time garbage collector.
    • JEP 334: JVM Constants API: New APIs for handling JVM constants.
    • JEP 230: Microbenchmark Suite: A suite for performance testing.
    • JEP 344: Abortable Mixed Collections for G1: Improvements to G1 Mixed GC.
    • JEP 346: Promptly Return Unused Committed Memory from G1: Optimizes memory return in G1 GC.
    • JEP 340: One AArch64 Port: Consolidation of AArch64 implementations.

  11. Overview of Reactive Programming with Project Reactor

    Reactor is an implementation of the reactive programming paradigm, which focuses on asynchronous data streams and the propagation of change. Unlike the 'pull-based' Iterator pattern used in imperative programming, reactive streams use a 'push-based' Publisher-Subscriber model. In this model, the Publisher notifies the Subscriber when new data is available.

    Reactive streams handle three types of signals:

    1. Data: Pushed via onNext (0 to N values).
    2. Error: Pushed via onError (terminates the stream).
    3. Completion: Pushed via onComplete (terminates the stream).

    This is summarized by the expression: onNext x 0..N [onError | onComplete].

  12. Overview of JVM ClassLoader

    The ClassLoader is a core JVM component responsible for reading the binary data stream of a class's information and converting it into a java.lang.Class object instance. This process occurs during the loading phase; the ClassLoader only affects how a class is loaded and cannot change the subsequent linking or initialization behaviors. The execution of the class is handled by the Execution Engine.