This section describes the Zookeeper technology

ZooKeeper summarizes a mind map to share with you

ZooKeeper aims to encapsulate key services that are complex and error-prone, and provide users with easy-to-use interfaces, efficient performance, and stable functions.

ZooKeeper contains a simple set of primitives providing Java and C interfaces. 2021 interview questions

The ZooKeeper code version, which provides an interface for distributed exclusive locks, elections, and queues, is in Zookeeper-3.4.3 SRC \recipes. Distribution locks and queues have Java and C versions, and elections have only Java versions.

The main function is to solve some data management problems frequently encountered in distributed applications, such as cluster management, unified naming management, distributed configuration management, distributed message queue, distributed lock, distributed notification coordination

Official website: Zookeeper.apache.org/

Zookeeper architecture

A ZK cluster has a Leader, one or more followers, they communicate with each other, and there is a client that accesses the ZK server.

The server has the Fast Fail feature. If the primary server fails, the primary server elects the secondary server to become the new primary server. The primary server mode is the most common mode.

Zookeeper namespace NODE by NODE, similar to the file system, in which each NODE is equal to the directories and files, through the path as a unique identifier, and file systems, each NODE has a corresponding data content, at the same time also can have child nodes, it coordinate is used to store data, such as status, configuration and location information, each NODE The amount of data stored is small, KB.

Watches are introduced

Zk adds, deletes, changes, and searches nodes to trigger listening

The Watch event is a one-time trigger that notifies the client that it is set up when the data it monitors changes

Zookeeper has been installed

Four servers

10.0.0.8 zk – 001

10.0.0.9 zk – 002

10.0.0.10 zk – 003

Zk – client 10.0.0.100

Download and install the JDK

tar zxf jdk-8u60-linux-x64.tar.gz

The mv jdk1.8.0 _60 / usr/local/JDK

export JAVA_HOME=/usr/local/jdk

export CLASSPATH=.:
$JAVA_HOME/lib/dt.jar:$JAVA_HOME/lib/tools.jar

export PATH=
$JAVA_HOME/bin:$PATH

source /etc/profile

java -version

[root@zk-001 ~]# java -version

Java version “1.8.0 comes with _60”

Java(TM) SE Runtime Environment (build 1.8.0_60-b27)

Java HotSpot(TM) 64-Bit Server VM (build 25.60-b23, mixed mode)

Download and install ZooKeeper

Wget www.apache.org/dist/zookee…

The tar ZXF zookeeper – 3.4.6. Tar. Gz

Zookeeper – 3.4.6 mv/usr/local/zookeeper

[root@zk-001 ~]# cd /usr/local/zookeeper/

Configuring environment Variables

export ZOOKEEPER_HOME=/usr/local/zookeeper

export PATH=
$ZOOKEEPER_HOME/bin:$PATH

source /etc/profile

They are the configuration of the

Three configuration modes

1. Pseudo-distribution mode

2. Completely distributed

3. Independent mode

Standalone mode configuration

[root@zk-001 zookeeper]# cd conf/

[root@zk-001 conf]# ll

total 12

-rw-rw-r– 1 1000 1000 535 Feb 20 2014 configuration.xsl

-rw-rw-r– 1 1000 1000 2161 Feb 20 2014 log4j.properties

-rw-rw-r– 1 1000 1000 922 Feb 20 2014 zoo_sample.cfg

[root@zk-001 conf]# cp zoo_sample.cfg zoo.cfg

[root@zk-001 conf]#vim zoo.cfg

The number of milliseconds of each tick

TickTime =2000 # Heartbeat check interval in milliseconds

the directory where the snapshot is stored.

do not use /tmp for storage, /tmp here is just

example sakes.

DataDir =/ TMP /zookeeper

the port at which the clients will connect

ClientPort =2181 # Port for clients to connect to

Cluster Mode Configuration

tickTime=2000

initLimit=10

syncLimit=5

//server.n=host:port1:port2

The number N must be the value in myID, which is located in the dataDIR directory and can only be an N value

//port1: indicates the leader port, which is connected to the followers as the leader

//port2: indicates the port to be connected by followers when the leader is elected

server.1=s1:2888:3888

server.2=s2:2888:3888

server.3=s3:2888:3888

The algorithm of ZK to deal with cluster faults is 2N +1, which is best deployed in odd number of machines. If multiple instances are configured on the same server, port conflicts should be paid attention to, which can be written as follows

server.1=s1:2888:3888

server.2=s2:2889:3889

server.3=s3:2887:3887

The configuration process is as follows

Configuring the hosts file

vim /etc/hosts

10.0.0.8 zk – 001

10.0.0.9 zk – 002

10.0.0.10 zk – 003

Configure the server configuration file

[root@zk-001 conf]# mkdir /tmp/zookeeper

[root@zk-001 conf]# cd /tmp/zookeeper/

[root@zk-001 zookeeper]# echo 8 >myid

[root@zk-001 conf]# egrep -v “^#|^$” zoo.cfg

tickTime=2000

initLimit=10

syncLimit=5

dataDir=/tmp/zookeeper

clientPort=2181

server.8=zk-001:2888:3888

server.9=zk-002:2888:3888

server.10=zk-003:2888:3888

[root@zk-002 ~]# mkdir /tmp/zookeeper

[root@zk-002 ~]# cd /tmp/zookeeper/

[root@zk-002 zookeeper]# echo 9 >myid

[root@zk-002 zookeeper]# ll

total 4

-rw-r–r– 1 root root 2 May 13 15:51 myid

[root@zk-002 zookeeper]# cd /usr/local/zookeeper/conf/

[root@zk-002 conf]# cp zoo_sample.cfg zoo.cfg

[root@zk-002 conf]# vim zoo.cfg

tickTime=2000

initLimit=10

syncLimit=5

dataDir=/tmp/zookeeper

clientPort=2181

server.8=zk-001:2888:3888

server.9=zk-002:2888:3888

server.10=zk-003:2888:3888

[root@zk-003 ~]# mkdir /tmp/zookeeper

[root@zk-003 ~]# cd /tmp/zookeeper/

[root@zk-003 zookeeper]# echo 10 >myid

[root@zk-003 zookeeper]# cd /usr/local/zookeeper/conf/

[root@zk-003 conf]# cp zoo_sample.cfg zoo.cfg

[root@zk-003 conf]# vim zoo.cfg

tickTime=2000

initLimit=10

syncLimit=5

dataDir=/tmp/zookeeper

clientPort=2181

server.8=zk-001:2888:3888

server.9=zk-002:2888:3888

server.10=zk-003:2888:3888

Start the service

[root@zk-001 bin]# zkServer.sh start

JMX enabled by default

Using config: /usr/local/zookeeper/bin/.. /conf/zoo.cfg

Starting zookeeper … STARTED

[root@zk-002 bin]# zkServer.sh start

JMX enabled by default

Using config: /usr/local/zookeeper/bin/.. /conf/zoo.cfg

Starting zookeeper … STARTED

[root@zk-003 bin]# zkServer.sh start

JMX enabled by default

Using config: /usr/local/zookeeper/bin/.. /conf/zoo.cfg

Starting zookeeper … STARTED

Check the status

[root@zk-001 conf]# zkServer.sh status

JMX enabled by default

Using config: /usr/local/zookeeper/bin/.. /conf/zoo.cfg

Mode: follower

[root@zk-002 conf]# zkServer.sh status

JMX enabled by default

Using config: /usr/local/zookeeper/bin/.. /conf/zoo.cfg

Mode: follower

[root@zk-003 conf]# zkServer.sh status

JMX enabled by default

Using config: /usr/local/zookeeper/bin/.. /conf/zoo.cfg

Mode: leader

You can see that the leader has been elected, indicating that the configuration is correct

Tests the failover after a leader failure

[root@zk-003 conf]# jps

2694 Jps

2430 QuorumPeerMain

[root@zk-003 conf]# kill 2430

[root@zk-003 conf]# jps

2724 Jps

[root@zk-002 conf]# zkServer.sh status

JMX enabled by default

Using config: /usr/local/zookeeper/bin/.. /conf/zoo.cfg

Mode: follower

[root@zk-001 conf]# zkServer.sh status

JMX enabled by default

Using config: /usr/local/zookeeper/bin/.. /conf/zoo.cfg

Mode: leader

You can see that the ZK-001 server has been elected the new leader

Zookeeper client four-character command

Conf Configuration information

Cons Connection Information

Dump unprocessed session nodes

Envi Environment information

Reqs did not process the request

Stat Statistics

Details about the WCHS server Watch

WCHP Lists the server information in the specified path

/ root @ zk – 003 ~ # echo the conf | nc 10.0.0.8 2181

clientPort=2181

dataDir=/tmp/zookeeper/version-2

dataLogDir=/tmp/zookeeper/version-2

tickTime=2000

maxClientCnxns=60

minSessionTimeout=4000

maxSessionTimeout=40000

serverId=8

initLimit=10

syncLimit=5

electionAlg=3

electionPort=3888

quorumPort=2888

peerType=0

/ root @ zk – 003 ~ # echo envi | nc 10.0.0.8 2181

Environment:

Zookeeper. version=3.4.6-1569965, built on 02/20/2014 09:09 GMT

host.name=zk-001

Java version = 1.8.0 comes with _121

java.vendor=Oracle Corporation

Java. Home = / usr/lib/JVM/Java — 1.8.0 comes with its 1.8.0.121-0. Bl3. El6_8. X86_64 / jre

java.class.path=/usr/local/zookeeper/bin/.. /build/classes:/usr/local/zookeeper/bin/.. /build/lib/.jar:/usr/local/zookeeper/bin/.. / lib/slf4j – log4j12-1.6.1. Jar: / usr/local/zookeeper/bin /.. / lib/slf4j – API – 1.6.1. Jar: / usr/local/zookeeper/bin /.. / lib/netty – 3.7.0. Final. Jar: / usr/local/zookeeper/bin /.. / lib/log4j – 1.2.16. Jar: / usr/local/zookeeper/bin /.. / lib/jline – 0.9.94. Jar: / usr/local/zookeeper/bin /.. / zookeeper – 3.4.6. Jar: / usr/local/zookeeper/bin /.. /src/java/lib/.jar:/usr/local/zookeeper/bin/.. /conf:

java.library.path=/usr/java/packages/lib/amd64:/usr/lib64:/lib64:/lib:/usr/lib

java.io.tmpdir=/tmp

java.compiler=

os.name=Linux

os.arch=amd64

OS, version = 2.6.32-504. The el6. X86_64

user.name=root

user.home=/root

user.dir=/usr/local/zookeeper/conf

/ root @ zk – 003 ~ # echo stat | nc 10.0.0.8 2181

Zookeeper version: 3.4.6-1569965, built on 02/20/2014 09:09 GMT

Clients:

/ 10.0.0.10:411920

Latency min/avg/max: 0/0/0

Received: 4

Sent: 3

Connections: 1

Outstanding: 0

Zxid: 0x200000000

Mode: leader

Node count: 4

Zookeeper client command

Run the zkcli. sh command to connect to the server

zkCli.sh -server zk-001:2181

- server 10.0.0.9:2181Copy the code

[root@zk-001 ~]# zkCli.sh -server zk-002:2181

Connecting to zk-002:2181

WATCHER::

WatchedEvent state:SyncConnected type:None path:null

[zk: zK-002:2181 (CONNECTED) 0

ZooKeeper -server host:port cmd args

    stat path [watch]

    set path data [version]

    ls path [watch]

    delquota [-n|-b] path

    ls2 path [watch]

    setAcl path acl

    setquota -n|-b val path

    history

    redo cmdno

    printwatches on|off

    delete path [version]

    sync path

    listquota path

    rmr path

    get path [watch]

    create [-s] [-e] path data acl

    addauth scheme auth

    quit

    getAcl path

    close

    connect host:port
Copy the code

[zk: zk-002:2181(CONNECTED) 1] ls /

List the contents of the directory

[zookeeper]

[zk: zk-002:2181(CONNECTED) 2] ls /zookeeper

[quota]

[zk: zk-002:2181(CONNECTED) 3] ls /zookeeper/quota

[]

[zk: zk-002:2181(CONNECTED) 4] create /root testfile

Create directories and data

Created /root

[zk: zK-002:2181 (CONNECTED)5]get /root

testfile

cZxid = 0x200000002

ctime = Sat May 13 20:09:52 CST 2017

mZxid = 0x200000002

mtime = Sat May 13 20:09:52 CST 2017

pZxid = 0x200000002

cversion = 0

dataVersion = 0

aclVersion = 0

ephemeralOwner = 0x0

dataLength = 8

numChildren = 0

[zk: zk-002:2181(CONNECTED) 6] set /root testfile-001

cZxid = 0x200000002

ctime = Sat May 13 20:09:52 CST 2017

mZxid = 0x200000003

mtime = Sat May 13 21:04:17 CST 2017

pZxid = 0x200000002

cversion = 0

dataVersion = 1

aclVersion = 0

ephemeralOwner = 0x0

dataLength = 12

numChildren = 0

Note that ZK cannot create multiple nodes at once

[zk: zk-002:2181(CONNECTED) 7] create /root/s1/s1-1

[zk: zK-002:2181 (CONNECTED) 8] ls /root

[]

[zk: zk-002:2181(CONNECTED) 9] create /root/s1 s1-data

Created /root/s1

[zk: zk-002:2181(CONNECTED) 10] create /root/s2 s2-data

Created /root/s2

[zk: zk-002:2181(CONNECTED) 11] create /root/s3 s3-data

Created /root/s3

[zk: zk-002:2181(CONNECTED) 13] ls /root

[s3, s1, s2]

Check the status

[zk: zk-002:2181(CONNECTED) 14] stat /root

cZxid = 0x200000002

ctime = Sat May 13 20:09:52 CST 2017

mZxid = 0x200000003

mtime = Sat May 13 21:04:17 CST 2017

pZxid = 0x200000006

cversion = 3

dataVersion = 1

aclVersion = 0

ephemeralOwner = 0x0

dataLength = 12

numChildren = 3

Delete the directory

[zk: zk-002:2181(CONNECTED) 15] delete /root/s3

[zk: zk-002:2181(CONNECTED) 16] ls /root

[s1, s2]

disconnect

[zk: zk-002:2181(CONNECTED) 17] close

2017-05-13 21:13:00,603 [myID :] -info [main:ZooKeeper@684] -session: 0x95C0122eFA50000 Closed 2017-05-13 21:13:00,603 [myID :] -info [main:ZooKeeper@684] -session: 0x95C0122eFA50000 Closed

2017-05-13 21:13:00,604 [myID :] -info [main-eventThread :ClientCnxn$EventThread@512] -EventThread Shut Down

Reconnect the

Since the data is consistent across the ZK servers, THIS time I connect to another server

[zk: zk-002:2181(CLOSED) 18] connect zk-001:2181

[zk: zk-001:2181(CONNECTED) 19] get /root

testfile-001

cZxid = 0x200000002

ctime = Sat May 13 20:09:52 CST 2017

mZxid = 0x200000003

mtime = Sat May 13 21:04:17 CST 2017

pZxid = 0x200000007

cversion = 4

dataVersion = 1

aclVersion = 0

ephemeralOwner = 0x0

dataLength = 12

numChildren = 2

[zk: zk-001:2181(CONNECTED) 20] get /root/s1

s1-data

cZxid = 0x200000004

ctime = Sat May 13 21:07:42 CST 2017

mZxid = 0x200000004

mtime = Sat May 13 21:07:42 CST 2017

pZxid = 0x200000004

cversion = 0

dataVersion = 0

aclVersion = 0

ephemeralOwner = 0x0

dataLength = 7

numChildren = 0

The last

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