java what is distributed

What is a distributed system?

To understand distributed systems, you mainly need to understand two aspects:

1. A distributed system must be a system composed of multiple nodes.

Among them, nodes refer to computer servers, and these nodes are generally not isolated, but interconnected.

2. Our nodes are deployed on these connected nodes, and mutual operations will be coordinated.

For users of distributed systems, what they face is just a server that provides the services that users need. In fact, these services are a distributed system composed of many servers behind them, so distributed The system looks like a supercomputer.

For example, Taobao is used by everyone. It is a distributed system in itself. When we access the Taobao website through a browser, behind this request is a huge distributed system providing services for us. The entire system Some are responsible for request processing, some are responsible for storage, and some are responsible for calculation. In the end, they coordinate with each other to return the final results and present them to the user.

The main features of using distributed systems are:

1. Increase system capacity. Our business volume is getting larger and larger, and to be able to cope with the growing business volume, the performance of one machine can no longer meet the requirements. We need multiple machines to cope with large-scale application scenarios. Therefore, we need to split the business system vertically or horizontally and turn it into a distributed architecture.

2. Enhance system availability. Our business is becoming more and more critical and we need to improve the availability of the entire system architecture, which means that there cannot be a single point of failure in the architecture. In this way, the entire system will not become unavailable due to the failure of one machine. Therefore, it is necessary to redundant the system through a distributed architecture to eliminate single points of failure and thereby improve system availability.

3. Because of modularity, system modules are more reusable.

4. Because the software service module is split, the development and release speed can be paralleled and become faster.

5. The system is more scalable.

6. The team collaboration process will also be improved.

There are three types of distributed systems:

1. Distributed processing, but there is only one total database and no local database.

2. Hierarchical processing, each layer has its own database.

3. A fully decentralized distributed network without a central control part, and there can be many ways of contact between nodes, such as loose connection, tight connection, dynamic connection, broadcast Notification-style connections, etc.

What is JAVA distributed application?

A large system is often divided into several subsystems. A subsystem can be deployed on multiple JVMs on one machine or on multiple machines. But each system is not independent, not completely independent. They need to communicate with each other and jointly implement business functions.

In a word: Distribution means distributing back-end work to multiple hosts through a computer network, and multiple hosts work together to complete the work.

Main ways to achieve distributed implementation

Technology used in distributed applications: network communication, message-based inter-system communication and remote call-based inter-system communication .

Disadvantage: It will increase the complexity of the technology.

The message-based system communication method mainly uses network protocols, such as TCP/IP protocol.

Communication between systems also requires data processing, such as synchronous IO and asynchronous IO.

Remote calling realizes communication between systems: transparently calling the remote Java implementation by calling the local Java interface method. The specific details are implemented in a framework.

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