JVM热身
此文是作者英文原文的翻译文章，英文原文在：http://todzhang.com/posts/2018-06-10-jvm-warm-up/
JVM预热
“低延迟”的Java虚拟机应用在一些应用场景下是对系统至关重要对一个指标。比如说在外汇交易系统等金融业核心系统中。此文就是探讨一下如何运用Java虚拟机预热来提高系统效率。
优化几调整JVM中每个进程过程称为预热
请记住，对于低延迟的应用程序，我们需要预先缓存所有类-以便在运行时访问它们时立即可用。
逃逸分析
逃逸分析是Java Hotspot Server编译器可以用来分析新对象使用范围并决定是否在Java堆上分配它的一种技术。 根据逃逸分析，对象的转义状态可能是以下之一：
-
GlobalEscape –对象转义方法和线程。例如，对象存储在静态字段中，或者存储在转义对象的字段中，或者作为当前方法的结果返回。
-
ArgEscape –作为参数传递或由参数引用但在调用过程中不会全局转义的对象。通过分析被调用方法的字节码确定此状态。
-
NoEscape –标量可替换对象，意味着可以从生成的代码中删除其分配。
经过逃逸分析后，服务器编译器从生成的代码中消除了标量可替换对象分配和关联的锁。服务器编译器还消除了对所有非全局转义对象的锁定。它不会用非全局转义对象的堆栈分配替换堆分配。
JIT积极地内联方法，从而消除了方法调用的开销。可以内联的方法包括静态，私有或最终方法，但如果可以确定它们没有被覆盖，则还可以包括公共方法。因此，后续的类加载可能会使先前生成的代码无效。因为在每个地方对每个方法进行内联都会花费时间，并且会生成不合理的大二进制文件，所以JIT编译器首先对热方法进行内联，直到达到阈值为止。为了确定哪些方法是热门的，JVM会保留计数器以查看方法被调用了多少次以及已执行了多少次循环迭代。这意味着内联仅在达到稳定状态后才发生，因此您需要重复进行一定次数的操作，然后才能有足够的概要分析信息供JIT编译器执行其工作。
您可以尝试打开Java命令行标志来窥视正在发生的事情，而不必试图猜测JIT在做什么：-XX：+ PrintCompilation -XX：+ UnlockDiagnosticVMOptions -XX：+ PrintInlining 这是他们的工作：
-XX：+ PrintCompilation：JIT编译发生时记录
-XX：+ UnlockDiagnosticVMOptions：启用其他标志，例如-XX：+ PrintInlining
GlobalEscape和ArgEscape对象必须在堆上分配，但是对于ArgEscape对象，可以删除一些锁定和内存同步开销，因为这些对象仅在调用线程中可见。
NoEscape对象可以自由分配，例如在堆栈上而不是堆上。实际上，在某些情况下，甚至根本不需要构造一个对象，而是仅构造该对象的标量值，例如对象Integer的int。同步也可能会被删除，因为我们知道只有这个线程会使用对象。例如，如果我们使用有些古老的StringBuffer（与StringBuilder相反，它具有同步方法），则可以安全地删除这些同步。
EA当前仅在C2 HotSpot编译器下可用，因此我们必须确保以-server模式运行。
为什么重要
从理论上讲，可以使用EA将NoEscape对象对象分配在堆栈上，甚至可以分配给CPU寄存器，从而可以非常快速地执行。
当我们在堆上分配对象时，我们开始消耗CPU缓存，因为对象被放置在堆上的不同地址上，彼此之间可能相距很远。这样，我们将快速耗尽L1 CPU缓存，并且性能会下降。另一方面，通过EA和堆栈分配，我们正在使用（很可能）已经在L1高速缓存中的内存。因此，EA和堆栈分配将改善我们的数据本地化。从性能的角度来看，这是很好的。
显然，当我们使用带有堆栈分配的EA时，垃圾收集的运行频率要低得多。这也许是最大的性能优势。回想一下，每次JVM运行一次完整的堆扫描时，我们都会从我们的CPU中获取性能，并且CPU高速缓存将很快耗尽。更不用说我们是否在服务器上调出了虚拟内存，从而导致GC破坏了性能。
EA的最重要优势不是性能。 EA允许我们使用Lambda，函数，流，迭代器等局部抽象，而不会造成任何明显的性能损失，从而使我们可以编写更好，更易读的代码。描述我们在做什么而不是如何完成的代码。
GC清理堆，而不是栈。当方法返回其调用方时，堆栈会自动清理，从而将堆栈指针重置为其以前的值。因此，GC将在执行EA / C2编译之前清理最终在堆栈中的对象。实际实例（或更确切地说，它们的相应表示形式）位于堆栈上，在EA优化的上下文中，堆栈上没有引用的对象。
JIT优化
一些JIT编译技术
内联是Java HotSpot VM使用的最常见的JIT编译技术之一，它是将方法的主体替换为调用该方法的位置的实践。内联节省了调用方法的成本；无需创建新的堆栈框架。默认情况下，Java HotSpot VM将尝试内联包含少于35个字节JVM字节码的方法。
Java HotSpot VM进行的另一种常见优化是单态调度，它依赖于观察到的事实，即通常情况下，没有一种方法会导致对象引用在大多数情况下属于一种类型，而在另一种类型中却存在另一种类型的路径。次。
您可能会认为Java的静态类型会排除通过不同代码路径具有不同类型的情况，但是请记住，子类型的实例始终是超类型的有效实例（在Barbara Liskov之后，该原理称为Liskov替换原理）。这种情况意味着方法可能有两条路径（例如，一条路径传递一个超类型的实例，而一条路径传递一个子类型的实例），这在Java的静态类型定义中是合法的（并且确实会在实践）。
但是，在通常情况下（单态情况），不会发生具有不同的依赖于路径的类型。因此，我们知道在传递的对象上调用方法时将调用的确切方法定义，因为我们无需检查实际上使用了哪个替代。这意味着我们可以消除执行虚拟方法查找的开销，因此JIT编译器可以发出优化的机器代码，通常比等效的C ++调用要快（因为在C ++情况下，无法轻松消除虚拟查找）。
两种Java HotSpot VM编译器模式使用不同的JIT编译技术，并且对于相同的Java方法，它们可以输出非常不同的机器代码。但是，现代Java应用程序通常可以同时使用两种编译模式。
Java HotSpot VM使用许多其他技术来优化JIT编译生成的代码。循环优化，类型锐化，死代码消除和内在函数只是Java HotSpot VM尝试尽可能多地优化代码的其他方式。技术通常是一层一层地放在另一层之上，因此一旦应用了一种优化，编译器便可能能够看到更多可以执行的优化。
编译模式
在Java HotSpot VM内部，实际上有两个单独的JIT编译器模式，分别称为C1和C2。 C1用于需要快速启动和坚如磐石的优化的应用； GUI应用程序通常是此编译器的理想选择。另一方面，C2最初是用于长时间运行的（主要是服务器端）应用程序。在某些Java SE 7更高版本之前，分别使用-client和-server开关可以使用这两种模式。
两种编译器模式使用不同的技术进行JIT编译，并且对于相同的Java方法，它们可以输出非常不同的机器代码。但是，现代Java应用程序通常可以同时使用两种编译模式。为了利用这一事实，从某些Java SE 7更高版本开始，提供了称为分层编译的新功能。此功能在开始时使用C1编译器模式以提供更好的启动性能。一旦对应用程序进行了适当的预热，C2编译器模式将接管其工作，以提供更具攻击性的优化，并且通常提供更好的性能。随着Java SE 8的到来，分层编译现已成为默认行为。
Java内存监视工具
pemi$ jps | grep Main
50903 Main
pemi$ jmap -histo 50903 | head
num #instances #bytes class name
----------------------------------------------
1: 95 42952184 [I
2: 1079 101120 [C
3: 485 55272 java.lang.Class
4: 526 25936 [Ljava.lang.Object;
5: 13 25664 [B
6: 1057 25368 java.lang.String
7: 74 5328 java.lang.reflect.Field
jmap-内存映射
工具或选项的说明和用法 Java任务控制
Java Mission Control（JMC）
是用于HotSpot JVM的新JDK分析和诊断工具平台。它是一个具有高性能的工具套件，用于基本的监视，管理和生产时间分析以及诊断。 Java Mission Control最大限度地减少了性能分析开销，而性能开销通常是性能分析工具遇到的问题。请参阅Java Mission Control。
jcmd实用程序
jcmd实用程序用于将诊断命令请求发送到JVM，这些请求对于控制Java Flight Records很有用。 JFR用于通过飞行记录事件对JVM和Java应用程序进行故障排除和诊断。请参见jcmd实用程序。
Java VisualVM
该实用程序提供了一个可视界面，用于在Java应用程序在Java虚拟机上运行时查看有关Java应用程序的详细信息。此信息可用于对本地和远程应用程序进行故障排除，以及对本地应用程序进行性能分析。请参阅Java VisualVM。 JConsole实用程序
该实用程序是基于Java管理扩展（JMX）的监视工具。该工具使用Java虚拟机中的内置JMX工具来提供有关正在运行的应用程序的性能和资源消耗的信息。请参见JConsole。 jmap实用程序
该实用程序可以从Java进程，核心文件或远程调试服务器获取内存映射信息，包括堆直方图。请参阅jmap实用程序。 jps实用程序
该实用程序列出了目标系统上已检测到的Java HotSpot VM。该实用程序在嵌入式VM的环境中非常有用，也就是说，它是使用JNI Invocation API而不是Java启动器启动的。请参阅jps实用程序。 jstack实用程序
该实用程序可以从Java进程获取Java和本机堆栈信息。在Oracle Solaris和Linux操作系统上，该实用程序可以从核心文件或远程调试服务器中获取信息。请参阅jstack实用程序。 jstat实用程序
该实用程序使用Java中的内置工具来提供有关正在运行的应用程序的性能和资源消耗的信息。诊断性能问题（尤其是与堆大小和垃圾回收相关的问题）时可以使用该工具。请参见jstat实用程序。 jstatd守护程序
该工具是一个远程方法调用（RMI）服务器应用程序，它监视已检测Java虚拟机的创建和终止，并提供一个接口，以允许远程监视工具连接到在本地主机上运行的VM。请参见jstatd守护程序。 visualgc实用程序
该实用程序提供了垃圾收集系统的图形视图。与jstat一样，它使用Java HotSpot VM的内置工具。请参阅visualgc工具。 本机工具
$ jps
16217 MyApplication
16342 jps
The utility lists the virtual machines for which the user has access rights. This is determined by access-control mechanisms specific to the operating system. On Oracle Solaris operating system, for example, if a non-root user executes the jps utility, then the output is a list of the virtual machines that were started with that user's uid.
In addition to listing the PID, the utility provides options to output the arguments passed to the application's main method, the complete list of VM arguments, and the full package name of the application's main class. The jps utility can also list processes on a remote system if the remote system is running the jstatd daemon.
无GC的Java
没有GC的Java开发 Coral Blocks开发的所有产品都具有非常重要的功能，可以将零垃圾抛在后面。由于Java垃圾收集器（即GC）施加的延迟对于高性能系统是不可接受的，并且由于无法关闭GC，因此Java实时系统的最佳选择是根本不产生任何垃圾。想象一下，GC永远不会启动。想象一下一个高性能匹配引擎，其运行时间为微秒级，每秒发送和接收数十万条消息。如果GC在任何给定时间决定以1毫秒以上的延迟开始运行，则系统中的中断将是巨大的。因此，如果要使用Java开发具有最小方差和延迟的实时系统，最好的选择是正确执行此操作，而不会为GC创建任何垃圾。
热身，检查GC和采样
确保您的系统不产生任何垃圾的关键是从开始到完成数百万次预热您的关键路径，然后再检查数百万次内存分配。如果它随着迭代次数的增加而线性地分配内存，则很可能会产生垃圾，您应该使用堆栈跟踪
–end–
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Mysql Operator To Extract Json
“Believe you can and you’re halfway there.” - Theodore Roosevelt
Master Microfrontends
“The only way to do great work is to love what you do.” - Steve Jobs
How To Convert One Monolith Java System To Microservices
Whatever is worth doing is worth doing well.
How To Config JFR Java Flight Control
“Climb the mountains and get their good tidings. Nature’s peace will flow into you as sunshine flows into trees. The winds will blow their own freshness i...
How To Read Jdk Mission Control Report
Live the life you’ve imagined.
Jdk Mission Control Can Not Start In Macbook M1
“Climb the mountains and get their good tidings. Nature’s peace will flow into you as sunshine flows into trees. The winds will blow their own freshness i...
How To Keep Multiple Copy Paste Value In Macbook
“Winning is nice if you don’t lose your integrity in the process.” — Arnold Horshak
Google マップ内の写真のコメントが表示されない
紹介 私は、私のOppo Androidスマートフォンのアプリ「Googleマップ」で奇妙な問題が発生していることに気づきました。Googleマップで特定の場所（例えば「中央公園」）を検索すると、通常、このアプリは公園の写真やコメントリストを表示するはずです。例えば、誰かが公園の芝生や川の写真を投稿し、便利な場所...
Les commentaires des photos ne s’affichent pas dans Google Maps.
Introduction J’ai remarqué un problème étrange avec l’application “Google Maps” de mon téléphone Android Oppo. Lorsque vous recherchez un lieu sur Google Map...
Is Kerberos One Ssl/tls?
Nothing is as easy as it looks.
How To Save Expect Script Run Output To File Locally
Nothing is as easy as it looks.
Refind Java Concurrency
You are not a drop in the ocean, you are the entire ocean in a drop.
Refind Java Solid Principles
You are not a drop in the ocean, you are the entire ocean in a drop.
How To Extract Table Name From Sql By Python
You are not a drop in the ocean, you are the entire ocean in a drop.
How to find non-empty json value in mysql
You are not a drop in the ocean, you are the entire ocean in a drop.
master-cglib-in-java
You are not a drop in the ocean, you are the entire ocean in a drop.
What is shape function in python pandas
An honest days’ work makes for a good night’s sleep.
What is shape function in python pandas
Imagination is the key ingredient to a happy life.
What is default logic in python try except else
Keep an eye on the fruits of your labor.
Not just use git but know how git symbolic-ref work
Superheros come in all shapes and sizes.
Fix rejection error in Hexo
The heart can see what is invisible to the eye.
Guide to code productively, get more time back for you
The heart can see what is invisible to the eye.
Is Fibonacci sequence that starts with 0 or 1
The best way to predict the future is to create it.
To increase your productivity 10 times, learn expect and read this blog
Som are born beautiful. The rest of us have to work at it.
Treasure Bowl for SQL, helpful for your daily database jobs
Don’t be greedy. Half of something is better than all nothing.
How to fix most permission issues when using Git
The best way to predict the future is to create it.
One killer page to fix most permission issues when using Git
The best way to predict the future is to create it.
How to check your CPU model and Linux distribution in your AWS VM
Lift is short, enjoy the ride.
2022
Magic-in-Micronaut-JPA
The best way to predict the future is to create it.
谷歌地图里面照片的评论和照片在华为手机里面显示不出来
枝上柳棉吹又少, 天涯何处无芳草. –苏轼
Cannot find symbol class Generated or var
The best way to predict the future is to create it.
GraphQL noteworthy points
Life is like the ocean, it goes up and down.
Scripts bible for MySql
Be the Sun of your solar system.
Minium Workable Mvp Vimrc
”—————————————————————- “ 4. User interface “—————————————————————- “ Set X lines to the cursor when moving vertically set scrolloff=0
How to build unit/integration tests for Spring State Machine
Get busy living or get busy dying.
Magic after maven target spring-boot-run
Turn your wounds into wisdom
Bamboo pipeline deployment failure caused by Kubenetes Finalizer
Today a reader, tomorrow a leader.
Error in WSL in windows, command not found: sdk
Never stop learning, because life never stops teaching.
Could not write JSON: Value out of range. Value: “xxxxx” Radix:10
Life is really simple, but men insist on making it complicated.
Gemfire Geode Error on Peer or client version with ordinal xx not supported. Highest known version is 1.12.1 Client
Take the risk or lose the chance!
Password must not null in gemfire and geode, but I’ve assigned password in yaml properties file
Worries less, smile more!
One page to cover most commonly found errors for fat jar in SpringBoot
Kill time, or kiss time!
Awesome Shortcuts to boost productivity
One must learn by doing the thing; for though you think you know it, you have no certainty, until you try. —Sophocles
Core Java tips required an interview
Success is the sum of small efforts, repeated.
Tell me difference of truststore and keystore in short answer
Do what you say, say what you do.
GIT useful scripts or error solutions
Don’t wish for it, work for it.
Tell me difference of yarn install and npm install in short answer
Don’t find fault. Find a remedy.
Bible blog for most commonly found Gradle errors
People are smarter than you think. Give them a chance to prove themselves.
Pearls in Front end development
Be happy in front of people who don’t like you, it kills them.
Ruby from zero to hero
This is your life. Do what you love, and do it often.
Everything you’d know for Groovy interviews
Life is short. Don’t waste it with negative people who don’t appreciate you. Keep them in your heart but keep them out of your life.
To outstanding as professional MacBook pro user
The most effective way to do it, is to do it Homebrew The best practice is to run brew info before install new software. It will generally list what’s c...
Failed to install gem in Mac, incompatible architecture and missing psych
Burn your ego before it burns you.
IntelliJ Tips to boost your productivity 10 times
Don’t be afraid to make s splash.
Everything you’d know about state machine for interviews
Less expecting, more accepting.
Tips about algorithm resolving from Leetcode
Stay focused, believe that you can achieve at the highest level, surround yourself with others who believe in you and do not stray from your goals.
Solution center for Node errors
Fina a way. If there’s none, make one!
Triple your productivities by Visual studio code keyboard shortcuts
The sentence The quick brown fox jumps over the lazy dog uses every letter of the alphabet.
TypeScript noteworthy notes
The moment you start focusing on yourself, things start falling into place.
RXJS – reactive Programming like a hero
When love is real, it doesn’t lie, cheat, pretend or keep secrets.
Concurrency in Java
Little things make big things happens.
Linux Tips
Remember, some things have to end for better things to begin.
A taste of GraphQL
A good day starts with a good mindset!
A taste of GraphQL
A good day starts with a good mindset!
What’s inside magic in Spring Data JPA
A good day starts with a good mindset!
What’s inside magic in Spring Data JPA
A good day starts with a good mindset!
Why Spring turn a column name from camelNaming to snake_Naming
Don’t spend another year doing the same shit.
Some mistakes you’d avoid in java
With great power comes great responsibilities.
Untold stories for Jupiter, any differences JUnit 5 vs Junit 4
Don’t tell people your plans. Just show them your results!
Git commands you can show off for 100 years
Life is short, make a big splash!
FileNotFound Exception when loading data file in IntelliJ
Take time to do what makes your soul happy!
How to ace AWS certification just like play a game
Life isn’t about finding yourself. Life is about creating yourself.
Java Deep Notes
Java Deep Notes
Code to draw a Big H with all stars
Coding is everything! Code Now!
Code to draw a Big H with all stars
Coding is everything! Code Now!
Single vs Double precisions, float vs double data type
Leave nothing for tomorrow which can be done today. -Abraham Lincoln.
SkipTest-Not-Work-In-Multiple-models-project
Leave nothing for tomorrow which can be done today. -Abraham Lincoln.
SkipTest-Not-Work-In-Multiple-models-project
Leave nothing for tomorrow which can be done today. -Abraham Lincoln.
Maven error and solution on No such host is known
Don’t promis when you are hapy. Don’t reply when you’re angry and don’t decide when you’re sad Service keep on restarting If you spot service is restartin...
Maven error and solution on No such host is known
Don’t promis when you are hapy. Don’t reply when you’re angry and don’t decide when you’re sad
Gradle build stuck
Gradle build stuck, keep on running but never ending
2021
Save my eyes, let your cell phone to read screen content to you
Too much screen time
How logging system Bootstrapped in Spring Boot Application
Summary Following diagram demonstrated the process to bootstrap and use Logback for loggings in Spring Boot applciation.
SQLServer Error about This driver is not configured for integrated authentication
Symptoms When you are using integrated authentication (Kerberos connection) for MS SqlServer connection, there is one possible error :
How to copy files from resources folder in jar and save to a file
Why to extract resources from jar to local disk
Debug of SpringBoot run not working in IntelliJ
Normal approach to debug maven
How to watch specific kubenetes deployment by labels
How to watch specific kubenetes deployment by labels
Failed to talk to github.com from corporation network
Background It’s typical to get various network connection issues when you run commands within corporation network. For example, you’ll find diversed issues w...
Day-Day-Up-Java
More developer friendly Threa Sleep
How to user fire extinguisher
Summary As you know, staff and your safety is paramount. So what if emergency take place, such as fire in office, how to help yourself and your colleagues by...
Deep dive into ApplicationEvent in SpringBoot
Summary As you know, there are various event will be sent (multicast) when a specific story taken place.
2021-09-22-IT-Solutions-For-Remote-Learning
IT-Solutions-For-Remote-Learning.md
Deep dive into Kubernetes Client API
Summary To talk to K8s for getting data, there are few approaches. While K8s’ official Java library is the most widely used one. This blog will look into thi...
How to get CPU name, core, 64bit and speed in command line
Summary In windows operating system, if you want to get your CPU name, core, 64bit and speed in command line. Just follow below actions:
JetBrains/IntelliJ tips
Be a good person in real life, not in social media
Whitelabel Error Page
Summary Whitelabel Error Page is the default error page in Spring Boot web app. It provide a more user-friently error page whenever there are any issues when...
Google maps no photos reviews
Summary
谷歌地图里面照片的评论显示不出来
If you’d like to view solution in YouTube, check out at https://youtu.be/ICiwuqJ-yU8
Shall I still need booster even after I got dose 3?
The greatest wealth is health!
Debts in a nutshell
A debt security represents a debt owed by the issuer to an investor. Here, the investor acts as a lender to the issuer which may be a government, organisatio...
2020
How to process data from S3 download URL
S3 download URL As you know, AWS S3 object can be downloaded/processed by S3 download URL. I’m showing you two examples on how to process S3 Object by NIO f...
Debug Stuck IntelliJ
What happened to a debug job hanging in IntelliJ (IDEAS) IDE? You may find when you try to debug a class in Intellij but it stuck there and never proceed, e....
Awesome Kotlin
Difference with Scala Kotlin takes the best of Java and Scala, the response times are similar as working with Java natively, which is a considerable advantag...
Awesome tips for Chrome
Shortcuts & tips
JVM热身
此文是作者英文原文的翻译文章，英文原文在：http://todzhang.com/posts/2018-06-10-jvm-warm-up/
Awesome tips and shortcuts for Slack
Shortcuts for Slack
Awesome Reactive programming
Key points of Reactive Programming
Awesome Swift for iOS
Frame in Swift
Mock in kotlin
Argument Matching & Answers For example, you have mocked DOC with call(arg: Int): Intfunction. You want to return 1 if argument is greater than 5 and -1 ...
Mock in kotlin
Argument Matching & Answers For example, you have mocked DOC with call(arg: Int): Intfunction. You want to return 1 if argument is greater than 5 and -1 ...
Docker
Dockers Concepts
How to decode path parameters in All REST WebServices calls
How to decode path parameters in All REST WebServices calls
Curl
Linux Curl command
AOP
The concept of join points as matched by pointcut expressions is central to AOP, and Spring uses the AspectJ pointcut expression language by default.
Micrometer notes
As a general rule it should be possible to use the name as a pivot. Dimensions allow a particular named metric to be sliced to drill down and reason about th...
Pigeons in holes principle
# Pigeonhole principle
Awesome solutions for algorithm questions
你就会发现只要涉及递归的问题，都是 树的问题。
A Facial Recognition utility in a dozen of LOC
A Facial Recognition utility in a dozen of python LOC (Lines Of Code)
Awesome SSL certificates and HTTPS
What’s TLS TLS (Transport Layer Security) and its predecessor, SSL (Secure Sockets Layer), are security protocols designed to secure the communication betwee...
JVM warm up by Escape Analysis
Why JVM need warm up I don’t know how and why you get to this blog. But I know the key words in your mind are “warm” for JVM. As the name “warm up” suggested...
Java Concurrent Column 2
This is the second half about Java Concurrent of my blog
Java Concurrent
This blog is about noteworthy pivot points about Java Concurrent Framework Back to Java old days there were wait()/notify() which is error prone, while fr...
Algorithm notes from Leecode – 1
Algorithm Leetcode
2019
Conversations with God
Feelings is the language of the soul. If you want to know what’s true for you about something, look to how your’re feeling about.
Kafka In Spring
Enable Kafka listener annotated endpoints that are created under the covers by a AbstractListenerContainerFactory. To be used on Configuration classes as fol...
Terraform
Why Terraform
Kafka
Kafka
Mifid
FX Spot is not covered by the regulation, as it is not considered to be a financial instrument by ESMA, the European Union (EU) regulator. As FX is considere...
Foreign Exchange
currency pairs Direct ccy: means USD is part of currency pair Cross ccy: means ccy wihtout USD, so except NDF, the deal will be split to legs, both with...
2018
Seconds
nano seconds
Citrix receiver
Simple Binary Encoding (SBE)
Citrix receiver
“Cannot connect to remote desktop” with Citrix Receiver
Guice
A new type of Juice Put simply, Guice alleviates the need for factories and the use of new in your Java code. Think of Guice’s @Inject as the new new. You wi...
YAML
Key points All YAML files (regardless of their association with Ansible or not) can optionally begin with — and end with …. This is part of the YAML format a...
Distruptor
multithreading
Mockito
Feature
Protobuf
What are protocol buffers?
Sudo in a Nutshell
Sudo in a Nutshell Sudo (su “do”) allows a system administrator to give certain users (or groups of users) the ability to run some (or all) commands as root...
Zoo-keeper
ZK Motto the motto “ZooKeeper: Because Coordinating Distributed Systems is a Zoo.”
Presto DB
WHAT IS PRESTO?
Chronicle
Overview
Cucumber
Acceptance testing vs unit test It’s sometimes said that unit tests ensure you build the thing right, whereas acceptance tests ensure you build the right thi...
Scala
Scala String
akka framework of scala
philosophy The actor model adopts the philosophy that everything is an actor. This is similar to the everything is an object philosophy used by some object-o...
File Util in Apache Camel
FileUtil.class
Apache Camel
Camel’s message model In Camel, there are two abstractions for modeling messages, both of which we’ll cover in this section. org.apache.camel.Message—The ...
QuickFixJ
Settings
JXM
Exporting your beans to JMX The core class in Spring’s JMX framework is the MBeanExporter. This class is responsible for taking your Spring beans and registe...
Solace MQ
Solace PubSub+ It is a message broker that lets you establish event-driven interactions between applications and microservices across hybrid cloud environmen...
Apigee
App deployment, configuration management and orchestration - all from one system. Ansible is powerful IT automation that you can learn quickly.
Ansible
Ansible: What Is It Good For? Ansible is often described as a configuration management tool, and is typically mentioned in the same breath as Chef, Puppet, a...
flexbox
How Flexbox works — explained with big, colorful, animated gifs
Jboss tips
commands:
Locking and multithreading
Single Writer principle
KDB
KDB However kdb+ evaluates expressions right-to-left. There are no precedence rules. The reason commonly given for this behaviour is that it is a much simple...
Foreign Exchange
Foreign Exchange markets
Portactor
Better to use smart wait
Agile and SCRUM
Key concept In Scrum, a team is cross functional, meaning everyone is needed to take a feature from idea to implementation.
DevOps-Philosophy
:100:DevOps Model Defined
rxjs pipe in depth
https://stormforger.com/blog/2016/07/08/types-of-performance-testing/
How to setup nodejs to install package from intranet
Error of ‘ECONNRESET’ You may face error ECONNRESET from intranet, even appropriate proxy tools (e.g. cntlm) is running. The errors may looks like ```bash $ ...
Strategy-Of-Openshift-Releases
Release & Testing Strategy There are various methods for safely releasing changes to Production. Each team must select what is appropriate for their own ...
NodeJs Notes
commands to read files var lineReader = require(‘readline’).createInterface({ input: require(‘fs’).createReadStream(‘C:\dev\node\input\git_reset_files.tx...
Minium Viable Product
https://blog.leanstack.com/minimum-viable-product-mvp-7e280b0b9418
What is difference between declarations, providers and import in NgModule
What is difference between declarations, providers and import in NgModule
CORS :Cross-Origin Resource Sharing
Cross-Origin Request Sharing - CORS (A.K.A. Cross-Domain AJAX request) is an issue that most web developers might encounter, according to Same-Origin-Policy,...
ngrx
Why @Effects? In a simple ngrx/store project without ngrx/effects there is really no good place to put your async calls. Suppose a user clicks on a button or...
iOS programming
View A view is also a responder (UIView is a subclass of UIResponder). This means that a view is subject to user interactions, such as taps and swipes. Thus,...
2017
cloud computering
openshift vs openstack The shoft and direct answer is `OpenShift Origin can run on top of OpenStack. They are complementary projects that work well together....
cloud computering
Concepts Cloud computing is the on-demand demand delivery of compute database storage applications and other IT resources through a cloud services platform v...
Redux
whats @Effects You can almost think of your Effects as special kinds of reducer functions that are meant to be a place for you to put your async calls in suc...
reactive programing
The second advantage to a lazy subscription is that the observable doesn’t hold onto data by default. In the previous example, each event generated by the in...
common errors in NPM or node
code E503 code E503 when run npm install packages, e.g.
Container
The Docker project was responsible for popularizing container development in Linux systems. The original project defined a command and service (both named do...
promise vs observiable
The drawback of using Promises is that they’re unable to handle data sources that produce more than one value, like mouse movements or sequences of bytes in ...
Openshift tips
Commands bible
google analysis
How Page Value is calculated
JDK source
interface RandomAccess Marker interface used by List implementations to indicate that they support fast (generally constant time) random access. The primary ...
SSH SFTP
Secure FTP SFTP over FTP is the equivalant of HTTPS over HTTP, the security version
Setup WebSphere profiles and application in command line
Setup WebSphere profiles and application in command line
AWS Tips
After establishing a SSH session, you can install a default web server by executing sudo yum install httpd -y. To start the web server, type sudo service htt...
Oracle
ORA-12899: Value Too Large for Column
Spring notes
Spring Bean Life Cycle Callback Methods
Kindle notes
#《亿级流量网站架构核心技术》目录一览 TCP四层负载均衡 使用Hystrix实现隔离 基于Servlet3实现请求隔离 限流算法 令牌桶算法 漏桶算法 分布式限流 redis+lua实现 Nginx+Lua实现 使用sharding-jdbc分库分表 Disruptor+Redis...
Java JIT compiler
This is talking about Java JIT (Just-In-Time) compiler
Java Security Notes
Java Security well-behaved: programs should be prevent from consuming too much system resources
SeriableVersionUID
Noteworthy points about SeriableVersionUID in Java
R Language
s<-read.csv("C:/Users/xxx/dev/R/IRS/SHH_SCHISHG.csv") # aggregate s2<-table(s$Original.CP) s3<-as.data.frame(s2) # extract by Frequency ordered s3...
SSH and Cryptography
SFTP versus FTPS SS: Secure Shell An increasing number of our customers are looking to move away from standard FTP for transferring data, so we are ofte...
Eclipse notes
How do I remove a plug-in? Run Help > About Eclipse > Installation Details, select the software you no longer want and click Uninstall. (On Macintosh i...
Java JVM
Class loading subsystem
Maven-Notes
Maven philosophy “It is important to note that in the pom.xml file you specify the what and not the how. The pom.xml file can also serve as a documentatio...
Java New IO
Notes JDK 1.0 introduced rudimentary I/O facilities for accessing the file system (to create a directory, remove a file, or perform another task), accessi...
Network Protocols
Net Protocols
IT-Architect
SOA SOA is a set of design principles for building a suite of interoperable, flexible and reusable services based architecture. top-down and bottom-up a...
Algorithm
This page is about key points about Algorithm
Dead Lock
Concept
Java-Tricky-Tech-Questions.md
What is the difference between Serializable and Externalizable in Java? In earlier version of Java, reflection was very slow, and so serializaing large ob...
NavigableMap Misc
What is NavigableMap
Compare-In-Java
Concepts If you implement Comparable interface and override compareTo() method it must be consistent with equals() method i.e. for equal object by equals(...
Java Collections Misc
Difference between equals and deepEquals of Arrays in Java Arrays.equals() method does not compare recursively if an array contains another array on oth...
HashMap in JDK
Hashmap in JDK Some note worth points about hashmap Lookup process Step# 1: Quickly determine the bucket number in which this element may resid...
Java 8 Tips
This blog is listing key new features introduced in Java 8
Arbitrage vs Heading
What is the difference between arbitrage and hedging?
Java Enum Misc
Enum Misc
2016
Java GC notes
verbose:gc verbose:gc prints right after each gc collection and prints details about each generation memory details. Here is blog on how to read verbose gc
Hash Code Misc
contract of hashCode : Whenever it is invoked on the same object more than once during an execution of a Java application, the hashCode method must consis...
Apache Tips
Apache
Angulary Misc
Dependency Injection Angular doesn’t automatically know how you want to create instances of your services or the injector to create your service. You must co...
Random number in java
ThreadLocalRandom, SecureRandm, java.util.Random, java.math.Random
Java new features
JDK Versions JDK 1.5 in 2005 JDK 1.6 in 2006 JDK 1.7 in 2011 JDK 1.8 in 2014 Sun之前风光无限，但是在2010年1月27号被Oracle收购。 在被Oracle收购后对外承诺要回到每2年一个realse的节奏。但是20...
用10几行代码自己写个人脸识别程序
用10几行代码自己写个人脸识别程序
Eslastic Search
Eslastic Search
JSON lines
JSON lines
Python Scraphy
Python Scraphy
Simpler chronicle of CI(Continuous Integration) “乱弹系列”之持续集成工具
引言 有句话说有人的地方就有江湖，同样，有江湖的地方就有恩怨。在软件行业历史长河（虽然相对于其他行业来说，软件行业的历史实在太短了，但是确是充满了智慧的碰撞也是十分的精彩）中有一些恩怨情愁，分分合合的小故事，比如类似的有，从一套代码发展出来后面由于合同到期就分道扬镳，然后各自发展成独门产品的Sybase DB和微...
Head First Blockchina 3
Hyperledger Fabric for Mortals
【原创】深入浅出区块链系统：第二章
使用Solidity创建以太坊(Ethereum)智能合约(Smart Contract)
How to customize Sublime syntax highlights
Reference Sublime Scope Naming Syntax Guide
浅谈软件单元测试中的“断言” (assert)，从石器时代进步到黄金时代。
大家都知道，在软件测试特别是在单元测试时,必用的一个功能就是“断言”（Assert)，可能有些人觉得不就一个Assert语句，没啥花头，也有很多人用起来也是懵懵懂懂，认为只要是Assert开头的方法，拿过来就用。一个偶然的机会跟人聊到此功能，觉得还是有必要在此整理一下如何使用以及对“断言”的理解。希望可以帮助大家...
Head First Blockchina 1
深入浅出区块链系统：第一章. what you should know about blockchain
Kubernetes 与 Docker Swarm的对比
Kubernetes 和Docker Swarm 可能是使用最广泛的工具，用于在集群环境中部署容器。但是这两个工具还是有很大的差别。
漫谈开发设计中的一些‘原则’及’设计哲学’
在开发设计中有一些常用原则或者潜规则，根据笔者的经验，这里稍微总结一下最最常用的，以飨读者。
http methods
RFC origion http://www.w3.org/Protocols/rfc2616/rfc2616-sec9.html#sec9.1.2)
Spark-vs-Storm
The stark difference among Spark and Storm. Although both are claimed to process the streaming data in real time. But Spark processes it as micro-batches; wh...
微服务
可以想像一下，之前的传统应用系统，像是一个大办公室里面，有各个部门，销售部，采购部，财务部。办一件事情效率比较高。但是也有一些弊端，首先，各部门都在一个房间里。
unmodifiableList, unmodifiableSet,unmodifiableMap
What’s it Returns an unmodifiable view of the specified set. This method allows modules to provide users with “read-only” access to internal sets. Query ope...
kibana, view layer of elasticsearch
What’s Kibana kibana is an open source data visualization plugin for Elasticsearch. It provides visualization capabilities on top of the content indexed on...
kibana, view layer of elasticsearch
What’s Kibana kibana is an open source data visualization plugin for Elasticsearch. It provides visualization capabilities on top of the content indexed on...
Anatomy of ThreadLocal
Design philosophies
iConnect
UI HTML5, AngularJS, BootStrap, REST API, JSON Backend Hadoop core (HDFS), Hive, HBase, MapReduce, Oozie, Pig, Solr
Business Analysis
Purpose of BA 带来一些商业价值（收益） 解决业务痛点
Something about RESTful architect
REST API must be hypertext driver Roy’s interview
Data Structure
Binary Tree A binary tree is a tree in which no node can have more than two children. A property of a binary tree that is sometimes important is that th...
Useful bookmarks
eBooks list of various books Node.js
heavy load web application
Common solutions
tips in as400 IBM Emulator
Toggle crosshair
Mysql operator to extract JSON
“Be the change you wish to see in the world.” - Mahatma Gandhi
equity trading
Difference between mutal funds and hedge funds
SQL
Differences between not in, not exists , and left join with null
HTTPS/2
concepts
Github page commands notes
404 error for customized domain (such as godday) 404 There is not a GitHub Pages site here. Go to github master branch for gitpages site, manually add CN...
RenMinBi International
RQFII RQFII stands for Renminbi Qualified Foreign Institutional Investor. RQFII was introduced in 2011 to allow qualified foreign institutional investors to ...
JavaScript tips
includes() vs some()
Docker Errors and Fixes
Docker Errors
Load Balancing
Concepts LVS means Linux Virtual Server, which is one Linux built-in component.
Python
(‘—–Unexpected error:’, <type ‘exceptions.TypeError’>) datetime.datetime.now()
Storage Management
RAID RAID is Reductant Array Independent Disk,
CI and CD
Concepts
XA Transactions in 2PC
Description
Setup Git in Mint Linux
How to setup Git in Mint Linux =================================================
Database sharding
DB sharding in YHD
Microservices vs. SOA
Microservice Services are organized around capabilities, e.g., user interface front-end, recommendation, logistics, billing, etc. Services are small in ...
Java Class Loader
Codecache The maximum size of the code cache is set via the -XX:ReservedCodeCacheSize=N flag (where N is the default just mentioned for the particular com...