zk的树形数据模型是什么

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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fieldpublic 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-torypublic 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 forprivate 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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