Netty is a high-performance, asynchronous event-driven NIO framework. It provides support for TCP, UDP and file transfer. All IO operations of Netty are asynchronous and non-blocking. Through the Future-Listener mechanism, users can conveniently Actively obtain or obtain the IO operation results through the notification mechanism.

Although JDK provides a rich NIO class library, and there are many NIO learning routines on the Internet, it is difficult to directly use the Java NIO class library to develop a stable and reliable communication framework. It is not easy, for the following reasons:

1) NIO's class libraries and APIs are complicated and troublesome to use. You need to be proficient in Selector, Server Socket Channel
SocketChannel, ByteBuffer, etc.

2) You need to have other additional skills as a foundation, such as being familiar with Java multi-threaded programming. This is because NIO programming involves the Reactor mode. You must be very familiar with multi-threading and network programming in order to write high-quality NIO programs.

3) To complete the reliability capability, the workload and difficulty are very large. For example, the client faces problems such as disconnection and reconnection, network interruption, half-packet reading and writing, failed caching, network congestion, and abnormal code stream processing. The characteristic of NIO programming is that function development is relatively easy, but reliability capabilities need to be supplemented. The volume and difficulty are very large.

4) JDK NIO BUG, ??such as the notorious epoll bug, which will cause Selector to empty poll, eventually causing CPU 100%. The official claims that this problem has been fixed in updateI8 of the JDK16 version, but the problem still exists until the JDK1.7 version, but the probability of the BUG occurrence has been reduced, and it has not been fundamentally solved. This BUG and the problem tickets related to this BUG can be found at the following link:

http://bugsjava.com/bugdatabase/viewbug.do?bugid=6403933
http:/bugs.javacom/bugdatabase /viewbugdo?bugid=2147719

With the development of the open source NO framework, more and more commercial systems are currently adopting the method of directly integrating the open source NO framework to replace the previous self-developed solutions. Take Netty, the most mature NIO framework, as an example. It has been verified by hundreds of commercial projects. For example, Hadoop's RPC framework avro uses Netty as the underlying communication framework, real-time streaming computing framework Sum's underlying communication framework also uses Netty, and Twitter's internal RPC framework Finagle, whose underlying communication framework is also built on Netty.

The advantages of Netty are summarized as follows:

◎The API is simple to use and the development threshold is low.

◎Powerful function, preset with multiple encoding and decoding functions, supporting multiple mainstream protocols.

◎ Strong customization capabilities, the communication framework can be flexibly expanded through ChannelHandler.

◎High performance. Compared with other mainstream NO frameworks in the industry, Netty has the best overall performance.

◎Mature and stable, Nety has fixed all JDK NIO BUGs that have been discovered, and business developers no longer need to worry about N1O BUGs.

◎The community is active, the version iteration cycle is short, and bugs discovered can be fixed in time. At the same time, more new features will be added.

◎It has gone through large-scale commercial application tests and its quality has been verified. It has been successfully commercialized in many industries such as the Internet, big data, online games, enterprise applications, telecommunications software, etc., proving that it can fully meet the commercial applications of different industries.

Netty’s performance is so good, so our communication framework is designed and developed based on Netty.

This article refers to Li Linfeng's "Principles and Practices of Distributed Service Framework", compiled by Shanghai Shangxuetang Java training. Please return to this column to read more Java technical articles, obtain Java technical information or learning videos, please contact the customer service lady .

The following articles are worth reading: "Principles and Functional Characteristics of Distributed Service Architecture_Shanghai Java Training", "What is Microservice Architecture?" The difference between microservice architecture and SOA architecture", "RPC architecture and principles, and an introduction to the mainstream RPC framework in the industry", "Introduction to the classic vertical application framework-MVC framework"

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