• Device pixels and CSS pixels – web side


    Device pixelGives the screen resolution of any device you are using, which can be accessed through screen Get width / height.But it is not immutable. For example, you can right-click “display settings” – “zoom and layout” to change. If the zoom is 100%, it is 19201080, then scaling 150% is 1280720 CSS pixelIs the pixel […]

  • How does PHP traverse objects?


    Foreach is a very convenient and easy-to-use syntax for PHP. It is one of the most frequently contacted requests for almost every PHPer. Can objects be traversed by foreach? The answer is yes, but there is a condition that the traversal of an object can only obtain its public properties. //General traversal class A { […]

  • Where is Kafka metadata information stored and how to view it


    This paper mainly describes the following two parts: Storage mode of Kafka data;Kafka how to find message through offset.1. PrefaceWrite and introduce several important concepts of Kafka (refer to the brief introduction of Kafka in the previous blog): Broker: message middleware processing node. A Kafka node is a broker. Multiple brokers can form a Kafka […]

  • Basic modules of Kafka broker


    1.SocketServerAs a module for broker to provide socket services externally, socketserver is mainly used to receive socket connection requests and generate corresponding socketchannel objects to serve.The internal mainly includes three modules:Acceptor is mainly used to monitor socket connections;Processor is mainly used to forward socket requests and responses.Requestchannel is mainly used to cache socket requests and […]

  • Compare Apache Kafka and Apache pulsar to create work queues


    Original: Jesse Anderson Sijie Guo A common use case for using Kafka or pulsar is to create a work queue. These two technologies provide different implementations for implementing this use case. I will discuss ways to implement work queues in Kafka and pulsar and their comparative advantages. What is a work queue Work queue adds […]

  • Redis master-slave replication and optimization


    Introduction:Redis master-slave replication and optimization Redis master-slave replication and optimization Master slave replication Before we focus on master-slave replication, we should first consider what is the problem with a single machine? machine stoppage Capacity bottleneck QPS bottleneck These are all problems encountered by a single node, so master-slave replication (one master-slave, one master-slave and many […]

  • 14 – hook principle


    Hook overview HOOKChinese translation is “hook” or “hook”. In IOS reverse, refers toChange the program running processA technology of. Through hook technology, other people’s programs can execute their own code. This technique is often used in reverse engineering. Therefore, in the learning process, we should focus on understanding its principle, so as to effectively protect […]

  • Principle analysis of Apache Flink CDC batch stream fusion technology


    This article is reproduced from the official account of “good future technology”. The use of Flink CDC 2 is introduced in the case of Flink SQL, and the core design of CDC is interpreted. The main contents are as follows: case Core design Code explanation In August, Flink CDC released version 2.0.0. Compared with version […]

  • [Android] implementation of AES encryption algorithm


    1 import android.text.TextUtils; 2 import android.util.Base64; 3 import android.util.Log; 4 5 import javax.crypto.Cipher; 6 import javax.crypto.spec.IvParameterSpec; 7 import javax.crypto.spec.SecretKeySpec; 8 9 public class AESCBCUtils { 10 private static final String TAG = “AESCBCUtils”; 11 12 // CBC (cipher block chaining) mode, pkcs5padding complement mode 13 // AES is the encryption mode, CBC is the working […]

  • Array paging implementation in PHP (non database)


    In the business environment of daily development, we generally use MySQL statements to realize the function of paging. However, there are often some data that are not much, or only some array data defined in PHP need paging function. At this time, we don’t need to query the database every time. We can take out […]

  • Kafka knowledge summary and sharing of open source platform for java development


    Basic architecture of KafkaA complete Kafka message middleware should include the following nodes: Producer: the node that produces the message Consumer: node of consumer message Broker: the node that receives the message storage sent by the producer Zookeeper: manage and maintain broker clusters, save metadata information of broker clusters, and ensure high availability of clusters. […]

  • Big data development: Kafka log structure


    As an important component of big data technology ecology, Kafka is widely reused as a distributed production / consumption system, especially in the real-time streaming data processing scenario. In Kafka, log is the main scenario for data production and consumption. Today’s big data development, learning and sharing, let’s talk about the basis of Kafka log […]