qfzhangwei的专栏

1 是什么？ Zookeeper 是一个分布式协调服务，可用于服务发现，分布式锁，分布式领导选举，配置管理等。 Zookeeper 提供了一个类似于 Linux 文件系统的树形结构（可认为是轻量级的内存文件系统，但 只适合存少量信息，完全不适合存储大量文件或者大文件），同时提供了对于每个节点的监控与通知机制。Zookeeper 集群是一个基于主从复制的高可用集群. 2 角色? Leader Leader: 一个 Zookeeper 集群同一时间只会有一个实际工作的 Leader，它会发起并维护与各 F

1 原理思想 Nacos 采用的是 Pull 模式，但并不是简单的 Pull，而是一种长轮训机制，它结合 Push 和 Pull 两者的优势。客户端采用长轮训的方式定时发起 Pull 请求，去检查服务端配置信息是否发生了变更，如果发生了变更，则客户端会根据变更的数据获得最新的配置。所谓的长轮训，是客户端发起轮训请求之后，服务端如果有配置发生变更，就直接返回，如图所示。 如果客户端发起 Pull 请求后，发现服务端的配置和客户端的配置是保持一致的，那么服务端会先 “Hold” 住这个请求，也就是服务端拿到

一般是zk host地址配置错误，局域网集群配置错误； 解决方案： 检查host,ip配置情况 检查zk集群ip对应情况

单机模拟集群#定义配置文件如下 ：三个端口 clientPort=2182 clientPort=2183 clientPort=2184 三个数据目录 dataDir=/home/zoo/z2/data dataDir=/home/zoo/z3/data dataDir=/home/zoo/z4/data # The number of milliseconds of each tick tick

A 客户端成为master的过程1 启动server端 [~/zookeeper]$ ../zookeeper-3.4.9/bin/zkServer.sh start ../z1/z1.cfg2 启动cli端 [~/zookeeper]$ ../zookeeper-3.4.9/bin/zkCli.sh -server 27.0.0.1:2180,127.0.0.1:2182,127.0.0.1:

States and the Lifetime of a SessionThe lifetime of a session corresponds to the period between its creation and its end, whether it is closed gracefully or expires because of a timeout. To talk ab

ZooKeeper SessionsBefore executing any request against a ZooKeeper ensemble, a client must establish a session with the service. The concept of session is very important and quite critical for the ope

ZooKeeper Quorums In quorum mode, ZooKeeper replicates its data tree across all servers in the ensemble. But if a client had to wait for every server to store its data before continuing, the delays mi

ZooKeeper+ ArchitectureNow that we have discussed at a high level the operations that ZooKeeper exposes to applications, we need to understand more of how the servicec actually works. Applications make

ZooKeeper + Versions//CAS Each znode has a version number associated with it that is incremented every time its data changes. A couple of operations in the API can be executed conditionally: setData a

Watches and NotificationsBecause ZooKeeper is typically accessed as a remote service, accessing a znode every time a client needs to know its content would be very expensive: it would induce higher lat

Zookeeper–different modes for znodesPersistent and ephemeral znodesA znode can be either persistent or ephemeral. Apersistent znode /path can be deleted only through a call to delete. An ephemeral zno

Zookeeper API Overview Znodes may or may not contain data. If a znode contains any data, the data is stored as a byte array. The exact fomat of the byte array is specific to each application, and Zoo

ZooKeeper BasicsSeveral primitives used for coordination are commonly shared across many applications. Consequently, one way of designing a service used for coordination is to come up with a list of p

//（zk）分布式系统的并发来源Processes in a distributed system have two broad options for communication: they can exchange messages directly through a network, or read and write to some shared storage. Zookeeper us

The Zookeeper Mission Trying to explain what Zookeeper does for us is like trying to explain what a screwdriver can do for us. In very basic terms, a screwdriver allows us to turn or drive screws,

Building distributed systems is hard. A lot of the applications people use daily, however, depend on such systems, and it doesn’t look like we will stop relying on distributed computer systems any ti