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Background: Network environment reference: Cloud networking experience Two vpc networks in Shanghai and Beijing. The servers are distributed as follows: Let's talk about why we use TencentOS Server 3.1 (TK4) system. It's not because CentOS 8 doesn't provide long-term maintenance... By the way, experience Tencent cloud's open source tencentos. ...

subject Sparse vector Title screenshot:  thinking 60 point answer My first idea is to open a two-dimensional array, which is equivalent to opening a two-dimensional table with two rows and many columns (why do you say many co ...

1, Installation package download Link: https://pan.baidu.com/s/1G6V9u5PDyxlixZ2PwGWdJA Extraction code: q8mb Note: the above installation package is a zip package, which contains all the packages for installing CDH6.1. After downloading, unzip it 2, Upload the installation package to the master node Note: the installation directory here sh ...

This article mainly describes how mybatis is loaded and executed in springboot. Because there will be a lot of content involved, this time we will only explain the call relationship and key code points. In order to avoid the article being too long and sleepy to read, some details that do not affect the overall process will not be involved. Sou ...

Introduction: starting from an example of data duplication in nailing real person authentication scenario, this paper analyzes that the reason is idempotent failure caused by concurrency, and leads to the concept of idempotent. Aiming at the idempotent problem in concurrent scenario, a feasible methodology for realizing idempotent is proposed. ...

Tokens are generated by JWT (Json Web Token - a json format). The default generation is in uuid format, but we need to override this method to generate JWT format. As a response token, it responds from the server to the client. After receiving the JWT token, the client saves it in the client (such as localStorage), and then carries the token to ...

Characteristics of Unit function It is similar to void in java, but java is a key frame, not a type, which is very contradictoryUnit is not written. It also exists by default. Unit represents the ignored type returned without parameters package com.fyx.s1 fun main() { } fun convert() { } //Equivalent to the above fun convert1() : Unit{ ...

How HDFS works 1. NameNode and DataNode HDFS adopts master/slave architecture. An HDFS cluster consists of a NameNode and a certain number of datanodes. NameNode is a central server, which is responsible for managing the namespace of the file system and the access of clients to files. A DataNode in a cluster is usually one node, which is resp ...

Preparation for multi table query: three tables are created. Previously used user table, newly created role table, account table, user_role table. The specific parameters in the table are as follows: user table (mainly the header, which is filled in by itself): role table: account table: user_role table: After these classes are created, r ...

4. Create model 4.2 factory mode 4.2.1 general Requirements: design a coffee shop ordering system. Design a Coffee category and define its two subclasses (American Coffee and latte Coffee); Then design a Coffee store, which has the function of ordering Coffee. The design of specific classes is as follows: In java, everything is an object, and ...