这篇文章主要介绍“zk的树形数据模型是什么”，在日常操作中，相信很多人在zk的树形数据模型是什么问题上存在疑惑，小编查阅了各式资料，整理出简单好用的操作方法，希望对大家解答”zk的树形数据模型是什么”的疑惑有所帮助！接下来，请跟着小编一起来学习吧！
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zookeeper的数据模型是树结构
在内存数据库中存储了整颗树内容，包含所有节点路径，节点数据，状态信息
会定时将数据刷到磁盘上
数据模型表示主要有DataTree DataNode ZKDatabase
datatree是一颗树结构，不包含和客户端，网络，请求相关的业务逻辑
dataNode是数据存储的最小单元，保存了节点数据内容，ACL列表，状态，父节点引用和子节点列表
zkdatabase是内存数据库，管理zk所有会话，DataTree存储和事务日志，定时将日志刷写到磁盘
在zookeeper启动时，会通过磁盘的事务日志和快照文件恢复一个完整的内存数据库
属性相关
属性相关
private final NodeHashMap nodes;
//监听节点
private IWatchManager dataWatches;
//监听节点
private IWatchManager childWatches;
/** cached total size of paths and data for all DataNodes */
//总大小
private final AtomicLong nodeDataSize = new AtomicLong(0);
/** the root of zookeeper tree */
//zookeeper的根节点
private static final String rootZookeeper = "/";
/** the zookeeper nodes that acts as the management and status node **/
//状态管理节点
private static final String procZookeeper = Quotas.procZookeeper;
/** th will be the string thats stored as a child of root */
//root的一个子节点
private static final String procChildZookeeper = procZookeeper.substring(1);
/**
* the zookeeper quota node that acts as the quota management node for
* zookeeper
*/
//限额管理节点
private static final String quotaZookeeper = Quotas.quotaZookeeper;
/** thi是s- will be the string thats stored as a child of /zookeeper */
// /zookeeper的子节点
private static final String quotaChildZookeeper = quotaZookeeper.substring(procZookeeper.length() + 1);
/**
* the zookeeper config node that acts as the config management node for
* zookeeper
*/
//配置管理节点
private static final String configZookeeper = ZooDefs.CONFIG_NODE;
/** thi是s- will be the string thats stored as a child of /zookeeper */
// 子节点config节点
private static final String configChildZookeeper = configZookeeper.substring(procZookeeper.length() + 1);
/**
* the path trie that keeps track of the quota nodes in thi是s- datatree
*/
//限额节点关联
private final PathTrie pTrie = new PathTrie();
/**
* over-the-wire size of znode's stat. Counting the fields of Stat class
*/
//stat 类的field
public static final int STAT_OVERHEAD_BYTES = (6 * 8) + (5 * 4);
/**
* Thi是s- hashtable li是s-ts the paths of the ephemeral nodes of a session.
*/
//临时会话节点的相关路径
private final Map> ephemerals = new ConcurrentHashMap>();
/**
* Thi是s- set contains the paths of all container nodes
*/
// 容器节点的路径
private final Set containers = Collections.newSetFromMap(new ConcurrentHashMap());
/**
* Thi是s- set contains the paths of all ttl nodes
*/
//ttl node的相关路径
private final Set ttls = Collections.newSetFromMap(new ConcurrentHashMap());
private final ReferenceCountedACLCache aclCache = new ReferenceCountedACLCache();
// The maximum number of tree digests that we will keep in our hi是s-tory
public static final int DIGEST_LOG_LIMIT = 1024;
// Dump digest every 128 txns, in hex it's 80, which will make it easier
// to align and compare between servers.
public static final int DIGEST_LOG_INTERVAL = 128;
// If thi是s- i是s- not null, we are actively looking for a target zxid that we
// want to validate the digest for
private ZxidDigest digestFromLoadedSnapshot;
// The digest associated with the highest zxid in the data tree.
private volatile ZxidDigest lastProcessedZxidDigest;
// Will be notified when digest mi是s-match event triggered.
private final Li是s-t digestWatchers = new ArrayLi是s-t<>();
// The hi是s-torical digests li是s-t.
private LinkedLi是s-t digestLog = new LinkedLi是s-t<>();
private final DigestCalculator digestCalculator;
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