Zookeeper It is an open source distributed framework that provides coordination services for distributed frameworks Apache project

         Structure and of ZooKeeper data model Unix The file system is very similar , as a whole, it can be regarded as a tree, and each node is called a tree ZNode . every last ZNode It can be stored by default 1MB Data for each ZNode Fine Uniquely identified by its path.

         The services provided include: unified naming service, unified configuration management, unified cluster management, dynamic uplink and downlink of server nodes, soft load balancing, etc.

Zookeeper Configuration files in zoo.cfg The meaning of parameters in is interpreted as follows:

(1) Ticketime = 2000: Communication heartbeat time, heartbeat time between Zookeeper server and client, unit: Ms

(2) Distribute Zookeeper

[hadoop@ggl201 module]$ sudo xsync zookeeper-3.7.0/

(3) Configure server number

[hadoop@ggl201 zkData]$ vim myid
[hadoop@ggl202 zkData]$ vim myid
[hadoop@ggl203 zkData]$ vim myid


#Add the number corresponding to the server in the file (Note: there should be no blank lines at the top and bottom, and no spaces at the left and right)
#Add separately 
1 2 3

(4) Configuration zoo.cfg file

#Rename the zoo in the directory / opt/module/zookeeper-3.5.7/conf_ Sample.cfg is zoo.cfg
[hadoop@ggl201 conf]$ mv zoo_sample.cfg zoo.cfg

#Open the zoo.cfg file
[hadoop@ggl201 conf]$ vim zoo.cfg

#Modify data storage path configuration
dataDir=/opt/module/zookeeper-3.7.0/zkData

#Add the following configuration
#######################cluster##########################
server.1=ggl201:2888:3888
server.2=ggl202:2888:3888
server.3=ggl203:2888:3888

#Interpretation of configuration parameters
server.A=B:C:D.  
A Is a number indicating the server number;
Configure a file in cluster mode myid，This file is in dataDir Under the directory, there is a data in this file A The value of, Zookeeper Read this file at startup and get the data and zoo.cfg Compare the configuration information inside to determine which one it is server. 
B Is the address of this server;
C This is the server Follower With in the cluster Leader The port where the server exchanges information;
D It's in the cluster Leader The server is down. You need a port to re elect and choose a new one
Leader，This port is used to communicate with each other during the election.

#Synchronize the zoo.cfg configuration file
[hadoop@ggl201 conf]$ xsync zoo.cfg

(5) Cluster operation

#Start Zookeeper separately
[hadoop@ggl201 zookeeper-3.7.0]$ bin/zkServer.sh start
[hadoop@ggl202 zookeeper-3.7.0]$ bin/zkServer.sh start
[hadoop@ggl203 zookeeper-3.7.0]$ bin/zkServer.sh start

#View status
[hadoop@ggl201 zookeeper-3.7.0]$ bin/zkServer.sh status
ZooKeeper JMX enabled by default
Using config: /opt/module/zookeeper-3.7.0/bin/../conf/zoo.cfg
Client port found: 2181. Client address: localhost. Client SSL: false.
Mode: follower

[hadoop@ggl202 zookeeper-3.7.0]$ bin/zkServer.sh status
ZooKeeper JMX enabled by default
Using config: /opt/module/zookeeper-3.7.0/bin/../conf/zoo.cfg
Client port found: 2181. Client address: localhost. Client SSL: false.
Mode: follower

[hadoop@ggl203 zookeeper-3.7.0]$ bin/zkServer.sh status
ZooKeeper JMX enabled by default
Using config: /opt/module/zookeeper-3.7.0/bin/../conf/zoo.cfg
Client port found: 2181. Client address: localhost. Client SSL: false.
Mode: leader

3.2 electoral mechanism

(1) First start

  (2) Not the first start

3.3 cluster startup script

(1) Create the script in / home/hadoop/bin directory of ggl201

[hadoop@ggl201 zookeeper-3.7.0]$ cd /home/hadoop/bin/
[hadoop@ggl201 bin]$ vim zk.sh

  Add the following:

#!/bin/bash
case $1 in
"start"){
for i in ggl201 ggl202 ggl203
do
 echo ---------- zookeeper $i start-up ------------
ssh $i "/opt/module/zookeeper-3.7.0/bin/zkServer.sh 
start"
done
};;
"stop"){
for i in ggl201 ggl202 ggl203
do
 echo ---------- zookeeper $i stop it ------------ 
ssh $i "/opt/module/zookeeper-3.7.0/bin/zkServer.sh 
stop"
done
};;
"status"){
for i in ggl201 ggl202 ggl203
do
 echo ---------- zookeeper $i state ------------ 
ssh $i "/opt/module/zookeeper-3.7.0/bin/zkServer.sh 
status"
done
};;
esac

(2) Add execution permission

[hadoop@ggl201 bin]$ chmod +x zk.sh

(3) Test script

[hadoop@ggl201 zookeeper-3.7.0]$ zk.sh status
[hadoop@ggl201 zookeeper-3.7.0]$ zk.sh stop
[hadoop@ggl201 zookeeper-3.7.0]$ zk.sh start

(4) Distribute script

[hadoop@ggl201 bin]$ xsync zk.sh

4, Client command line operation

4.1 command line syntax

  (1) Start client

[hadoop@ggl201 zookeeper-3.7.0]$ bin/zkCli.sh -server ggl201:2181

  four point two   znode node data information

(1) View the information contained in the current node

        

(2) View current node details

         

         1> Czxid: create the transaction zxid of the node. Each time the ZooKeeper state is modified, a ZooKeeper transaction ID will be generated. The transaction ID is the total order of all modifications in ZooKeeper. Each modification has a unique zxid. If zxid1 is less than zxid2, zxid1 occurs before zxid2.
         2> CTime: the number of milliseconds that znode was created (since 1970)
         3> Mzxid: transaction zxid last updated by znode
         4> Mtime: the number of milliseconds the znode was last modified (since 1970)
         5> Pzxid: the last updated child node zxid of znode
         6> Cversion: change number of znode child node and modification times of znode child node
         7> Data version: znode data change number
         8> Aclversion: change number of znode access control list
         9> Ephemeral owner: if it is a temporary node, this is the session id of the znode owner. 0 if it is not a temporary node.

         10> Datalength: the data length of znode

        11> Numchildren: number of child nodes of znode