ZooKeeper 简介

什么是 ZooKeeper

官网地址：https://zookeeper.apache.org/

ZooKeeper is a centralized service for maintaining configuration information, naming, providing distributed synchronization, and providing group services. All of these kinds of services are used in some form or another by distributed applications. Each time they are implemented there is a lot of work that goes into fixing the bugs and race conditions that are inevitable. Because of the difficulty of implementing these kinds of services, applications initially usually skimp on them, which make them brittle in the presence of change and difficult to manage. Even when done correctly, different implementations of these services lead to management complexity when the applications are deployed.

ZooKeeper 为分布式程序提供分布式协调服务

ZooKeeper 为大型分布式计算提供开源的分布式配置服务、同步服务和命名注册。

ZooKeeper 设计目标

命名空间

ZooKeeper 允许分布式进程通过共享的层级命名空间（目录树）相互协调，该命名空间的组织类似于标准文件系统。名称空间由数据寄存器 (在 ZooKeeper 中称为 znodes )组成，它们类似于文件和目录

znodes 类似于文件和目录。说明 Znode 节点上既可以直接存储数据，也可以创建目录

高性能

ZooKeeper 数据保存在内存中，这意味着 ZooKeeper 可以获得高吞吐量和低延迟数。 ZooKeeper 的数据也会持久化存储。
高可用
ZooKeeper 实现重视高性能、高可用性和严格有序的访问。ZooKeeper 的性能方面意味着它可以用于大型分布式系统。可靠性方面使它不会成为单点故障。严格的顺序意味着可以在客户端实现复杂的同步原语。

所谓原语，一般是指由若干条指令组成的程序段，用来实现某个特定功能，在执行过程中不可被中断。