CentOs7.3 build ZooKeeper-3.4.9 stand-alone service

Overview#

Zookeeper is actually developed by Yahoo and is used as a framework for consistent processing in distributed applications. It was originally a by-product of the development of Hadoop. Due to the difficulty of consistency processing in distributed systems, other distributed systems do not need to laboriously reinvent the wheels, so zookeeper is widely used in subsequent distributed systems, so that zookeeper has become the basic component of various distributed systems. The importance of status can be imagined. The famous hadoop, kafka, dubbo are all based on zookeeper.

To understand what zookeeper does, you must first understand clearly what is consistency? **

The so-called consistency actually revolves around "seeing". Who can see? Can you see it? When did you see it? For example: Taobao backend sellers put a big promotion item in the backend and submit it to the main database through server A. Assuming that immediately after submission, there are users who go to query the item from the database through application server B, and a Phenomenon, the seller has successfully updated, but the buyer can't see it; and after a period of time, the data in the master database is synchronized to the slave database, and the buyer can check it.

Assuming that the buyer can see the seller’s update immediately after the seller’s update is successful, it is called strong consistency

If the buyer cannot see the content updated by the seller after the seller update is successful, it is called weak consistency**

After the seller is updated successfully, the buyer can finally see the seller's update after a period of time, which is called final consistency

"Conformance Agreement"

"ZooKeeper Application Scenarios"

"Distributed Architecture"

"Distributed ZooKeeper Series"

surroundings#

VMware version number: 12.0.0

CentOS version: CentOS 7.3.1611

ZooKeeper version: ZooKeeper-3.4.9.tar.gz

JDK environment: jdk-8u144-linux-x64.tar.gz

JDK 1.8 installation

Specific reference ["CentOs7.3 install JDK1.8"] (https://segmentfault.com/a/1190000010716919)

ZooKeeper installation#

1. Download ZooKeeper

cd /opt/
wget https://mirrors.tuna.tsinghua.edu.cn/apache/zookeeper/zookeeper-3.4.9/zookeeper-3.4.9.tar.gz

Or download and upload in the browser to the opt directory

2. Extract tar file##

cd /opt/
tar -zxf  zookeeper-3.4.9.tar.gz
cd zookeeper-3.4.9

Create a data folder to store data files

mkdir data  logs

Create a logs folder to store logs

mkdir logs  

3. Create configuration file##

Use the command vi conf/zoo.cfg to create a configuration file and open it, ps (in fact, there is a default configuration file under the directory conf, but there are too many comments, a lot of English, and too messy)

vi  /opt/zookeeper-3.4.9/conf/zoo.cfg

The edit content is as follows

tickTime =2000
dataDir =/opt/zookeeper-3.4.9/data
dataLogDir =/opt/zookeeper-3.4.9/logs
tickTime =2000
clientPort =2181
initLimit =5
syncLimit =2

Configuration file description

tickTime

• TickTime is the basic unit of the above two timeout configurations. For example, for initLimit, its configuration value is 5, indicating that its timeout period is 2000ms * 5 = 10 seconds.

dataDir

• The meaning of its configuration is similar to that in stand-alone mode, except that there is a myid file in cluster mode. The content of the myid file is only one line, and the content can only be a number between 1 and 255. This number is the id in server.id described above, which represents the id of the zk process.

dataLogDir

• If not provided, dataDir is used. The persistence of zookeeper is stored in these two directories. DataLogDir is the sequential log (WAL) that is placed. The dataDir puts a snapshot of the memory data structure for quick recovery. In order to maximize performance, it is generally recommended to separate dataDir and dataLogDir on different disks, so that the sequential write characteristics of disks can be fully utilized.

initLimit

• ZooKeeper cluster mode contains multiple zk processes, one of which is the leader, and the remaining processes are followers. When the follower initially establishes a connection with the leader, a considerable amount of data will be transmitted between them, especially the data of the follower is much behind the leader. initLimit configures the maximum time for synchronization after establishing a connection between follower and leader.

syncLimit

• Configure the maximum length of time for sending messages, requests and responses between follower and leader.

ZooKeeper operation#

Start service##

/opt/zookeeper-3.4.9/bin/zkServer.sh start

response

ZooKeeper JMX enabled by default
Using config:/opt/zookeeper-3.4.9/bin/../conf/zoo.cfg
Starting zookeeper ... STARTED

Connection service##

Connect to ZooKeeper service

/opt/zookeeper-3.4.9/bin/zkCli.sh

response

Connecting to localhost:21812017-08-2216:43:05,954[myid:]- INFO  [main:Environment@100]- Client environment:zookeeper.version=3.4.9-1757313, built on 08/23/201606:50 GMT
2017- 08- 2216:43:05,958[ myid:]- INFO  [main:Environment@100]- Client environment:host.name=node1
2017- 08- 2216:43:05,958[ myid:]- INFO  [main:Environment@100]- Client environment:java.version=1.8.0_144
2017- 08- 2216:43:05,967[ myid:]- INFO  [main:Environment@100]- Client environment:java.vendor=Oracle Corporation
2017- 08- 2216:43:05,967[ myid:]- INFO  [main:Environment@100]- Client environment:java.home=/usr/lib/jvm/jre
2017- 08- 2216:43:05,967[ myid:]- INFO  [main:Environment@100]- Client environment:java.class.path=/opt/zookeeper-3.4.9/bin/../build/classes:/opt/zookeeper-3.4.9/bin/../build/lib/*.jar:/opt/zookeeper-3.4.9/bin/../lib/slf4j-log4j12-1.6.1.jar:/opt/zookeeper-3.4.9/bin/../lib/slf4j-api-1.6.1.jar:/opt/zookeeper-3.4.9/bin/../lib/netty-3.10.5.Final.jar:/opt/zookeeper-3.4.9/bin/../lib/log4j-1.2.16.jar:/opt/zookeeper-3.4.9/bin/../lib/jline-0.9.94.jar:/opt/zookeeper-3.4.9/bin/../zookeeper-3.4.9.jar:/opt/zookeeper-3.4.9/bin/../src/java/lib/*.jar:/opt/zookeeper-3.4.9/bin/../conf:.:/lib/jvm/lib:/lib/jvm/jre/lib
2017- 08- 22 16:43:05,967 [ myid:] - INFO  [main:Environment@100] - Client environment:java.library.path=/usr/java/packages/lib/amd64:/usr/lib64:/lib64:/lib:/usr/lib
2017- 08- 22 16:43:05,967 [ myid:] - INFO  [main:Environment@100] - Client environment:java.io.tmpdir=/tmp
2017- 08- 22 16:43:05,967 [ myid:] - INFO  [main:Environment@100] - Client environment:java.compiler=<NA>
2017- 08- 22 16:43:05,967 [ myid:] - INFO  [main:Environment@100] - Client environment:os.name=Linux
2017- 08- 22 16:43:05,967 [ myid:] - INFO  [main:Environment@100] - Client environment:os.arch=amd64
2017- 08- 22 16:43:05,967 [ myid:] - INFO  [main:Environment@100] - Client environment:os.version=3.10.0-514.26.2.el7.x86_64
2017- 08- 22 16:43:05,968 [ myid:] - INFO  [main:Environment@100] - Client environment:user.name=root
2017- 08- 22 16:43:05,968 [ myid:] - INFO  [main:Environment@100] - Client environment:user.home=/root
2017- 08- 22 16:43:05,968 [ myid:] - INFO  [main:Environment@100] - Client environment:user.dir=/opt/zookeeper-3.4.9
2017- 08- 22 16:43:05,969 [ myid:] - INFO  [main:ZooKeeper@438] - Initiating client connection, connectString=localhost:2181 sessionTimeout=30000 watcher=org.apache.zookeeper.ZooKeeperMain$MyWatcher@506c589e
Welcome to ZooKeeper!
2017- 08- 22 16:43:06,011 [ myid:] - INFO  [main-SendThread(localhost:2181):ClientCnxn$SendThread@1032] - Opening socket connection to server localhost/0:0:0:0:0:0:0:1:2181. Will not attempt to authenticate using SASL (unknown error)
JLine support is enabled
2017- 08- 22 16:43:06,164 [ myid:] - INFO  [main-SendThread(localhost:2181):ClientCnxn$SendThread@876] - Socket connection established to localhost/0:0:0:0:0:0:0:1:2181, initiating session
2017- 08- 22 16:43:06,237 [ myid:] - INFO  [main-SendThread(localhost:2181):ClientCnxn$SendThread@1299] - Session establishment complete on server localhost/0:0:0:0:0:0:0:1:2181, sessionid = 0x15e091bf2020000, negotiated timeout = 30000

WATCHER::

WatchedEvent state:SyncConnected type:None path:null

[ zk: localhost:2181(CONNECTED) 0] 

service status##

/opt/zookeeper-3.4.9/bin/zkServer.sh status

response

ZooKeeper JMX enabled by default
Using config:/opt/zookeeper-3.4.9/bin/../conf/zoo.cfg
Mode: standalone

Out of service##

/opt/zookeeper-3.4.9/bin/zkServer.sh stop

response

bin/zkServer.sh stop
ZooKeeper JMX enabled by default
Using config:/opt/zookeeper-3.4.9/bin/../conf/zoo.cfg
Stopping zookeeper ... STOPPED

Recommended reading##

CentOs7.3 build ZooKeeper-3.4.9 Cluster cluster service

Contact

• Author: Peng Lei
• Source: http://www.ymq.io
• Email：[email protected]
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