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This article shows you what zookeeper is. It is concise and easy to understand. It will definitely brighten your eyes. I hope you can get something through the detailed introduction of this article.

What is zookeeper?

Zookeeper is a coordination service for users' distributed applications. Using it, you can solve some problems of distributed programs, such as the election of master nodes, distributed locks and so on.

Design goals of zookeeper

Simple and available

High availability

Order

The main concepts of zookeeper 1. Data node

Like linux's file system, a tree-shaped data structure

two。 Data node type

Temporary node

Bind to the life cycle of Session. If the Session is disconnected, the node will be deleted. Based on this feature, the node cannot have child nodes.

Persistent node

Effective node

This type of node can maintain atomic increment and be subdivided into ordered persistent and ordered temporary nodes.

Container node (version 3.5.3)

When the last child in the container is deleted, the node can be deleted (mainly for garbage collection)

3.Session

A connection session established between the client and the server

Main state

Start, connect, connected, close these four states, pay special attention to whether the session is invalid, is defined by the server, but the client can display the shutdown.

4.Watches1. Main features

One trigger

When there is a change in the data, notify the client. After passing once, the client needs to re-register watch the next time it changes. (however, many open source sdk have encapsulated these.)

Send client

Only after the client receives the success of the server can the client really listen to the message.

5.ACL permission

Create

You can create child nodes

Read

You can get data from a node

Write

Set data to a node

Delete

You can delete the data.

Admin

Permissions can be set

6. Application scenario

It can realize data publish / subscribe, load balance, master election, distributed queue, distributed lock and so on.

What is zookeeper above? have you learned any knowledge or skills? If you want to learn more skills or enrich your knowledge reserve, you are welcome to follow the industry information channel.

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