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客户端命令

当您连接到 ZooKeeper 服务器时,可以使用以下命令来与 ZooKeeper 进行交互:

ls:列出指定节点的子节点。
create:创建一个新节点。
delete:删除指定节点及其所有子节点。
get:获取指定节点的数据。
set:设置指定节点的数据。
stat:获取指定节点的元数据,例如节点的版本号、创建时间和修改时间等。
sync:将客户端缓存的数据与服务器同步。
exists:检查指定节点是否存在。
help:获取帮助信息。
quit:退出客户端。

Quorums

Simply put

ZooKeeper’s Quorum mechanism is used to ensure high availability and fault tolerance in a ZooKeeper cluster. In a Quorum-based ZooKeeper deployment, the cluster is divided into a set of nodes, each of which is called a server. These servers are further divided into two types: Leader and Follower.

A Quorum is a set of servers that participate in the decision-making process for the cluster. In ZooKeeper, a Quorum is formed by a majority of servers. For example, if a cluster has five servers, then a Quorum would consist of three servers.

In a Quorum-based ZooKeeper deployment, the Leader server is responsible for handling all write requests, while the Follower servers are responsible for handling read requests. The Leader server is elected by the Quorum using a leader election algorithm.

If the Leader server fails, then a new Leader is elected by the Quorum. This ensures that the cluster remains available even if one or more servers fail.

说明

ZooKeeper 的 Quorum 机制是保证 ZooKeeper 集群数据一致性和可用性的重要机制之一。Quorum 是指在 ZooKeeper 集群中,大多数节点必须达成一致才能进行操作。具体来说,Quorum 机制包括以下几个方面:

集群节点数目:ZooKeeper 集群中必须有奇数个节点,这样才能保证在出现网络分区等情况时,仍然有一个节点数目大于一半,从而保证整个集群的可用性。

Leader 选举:在 ZooKeeper 集群中,只有 Leader 节点可以处理客户端请求。当 Leader 节点失效时,其他节点会参与 Leader 选举,选举出新的 Leader 节点。

数据同步:ZooKeeper 集群中的数据是分布式存储的,因此需要进行数据同步。ZooKeeper 使用 Zab 协议来保证数据的一致性。在 Zab 协议中,Leader 节点负责将数据同步到其他节点。

Quorum 机制:在 ZooKeeper 集群中,只有在大多数节点达成一致时,才能进行数据修改等操作。例如,如果 ZooKeeper 集群中有 5 个节点,那么只有在 3 个节点达成一致时,才能进行数据修改等操作。

通过以上机制,ZooKeeper 可以保证数据的一致性和可用性。同时,Quorum 机制也是 ZooKeeper 分布式锁和分布式队列等功能的基础。

可视化工具

https://blog.csdn.net/ibigboy/article/details/125830426