Shulou(Shulou.com)06/02 Report--

Zookeeper introduction

ZooKeeper is a centralized service for maintaining configuration information, naming, and providing distributed synchronization and group services. All these types of services are used in the form of distributed applications. It has a reliable, scalable, distributed and configurable coordination mechanism to unify the state of the system.

Server planning

At least three servers are needed in the zookeeper cluster. Because of the limited resources, let's take three servers as an example.

Zookeeper deployment model

There are three ways to install Zookeeper, stand-alone mode, cluster mode and pseudo-cluster mode.

Stand-alone mode: Zookeeper runs on only one server, which is suitable for test environment

Pseudo-cluster mode: running multiple Zookeeper instances on a single physical machine

Cluster mode: Zookeeper runs on a cluster that is suitable for production environments. This computer cluster is called a "ensemble".

Zookeeper profile

The official configuration file template is zoo_sample.cfg, which we need to change to zoo.cfg when we use it in the real environment. Operate on 192.168.2.177

[root@rocketmq-nameserver1 conf] # vim zoo.cfgtickTime=2000initLimit=10syncLimit=5dataDir=/wdata/zookeeperdataLogDir=/wdata/zookeeper/logsclientPort=2181#maxClientCnxns=60#autopurge.snapRetainCount=3#autopurge.purgeInterval=1server.1=192.168.2.177:2888:3888server.2=192.168.2.178:2888:3888server.3=192.168.2.180:2888:3888

Profile description:

Server.X=A:B:C

Where X is the server number, An is the IP address of the node server, B is the Leader communication port, and C is the Zookeeper Leader election port

DataLogDir:zookeeper transaction log directory

DataDir:zookeeper data storage directory

ClientPort: client listening port

SyncLimit: the maximum number of heartbeats that can be tolerated between the flower server (F) and the leader (L) server in the cluster.

InitLimit: the maximum number of heartbeats (number of tickTime) that can be tolerated during the initial connection between the flower server (F) and the leader server (L) in the cluster.

TickTime:CS communication heartbeat time, the heartbeat is maintained between the client and the server or between the server and the server, that is, a heartbeat is sent every tickTime time. Not only can the heartbeat be used to monitor the working state of the machine, but also the communication time between Flower and Leader can be controlled by heartbeat. By default, FL sessions are often twice the heartbeat interval.

Zookeeper cluster

Before building a Zookeeper cluster, we need to modify the environment variables of the system

Modified on 192.168.2.177, 192.168.2.178 and 192.168.2.180 respectively

[root@rocketmq-nameserver1 ~] # vim .bash _ profileexport JAVA_HOME=/usr/local/jdk1.8.0_201export ZOOKEEPER_HOME=/usr/local/zookeeper-3.4.13export PATH=$PATH:$JAVA_HOME/bin:$ZOOKEEPER_HOME/bin

Copy Profil

We distributed the configured configuration files to two other servers (178 and 180)

For i in 178 180; do scp zoo.cfg root@192.168.2.$i; done

We add the server number file to the three servers. The content in the file is the server number, and the server number must correspond to the number in the configuration file, otherwise the cluster cannot be started.

[root@rocketmq-nameserver1 zookeeper] # vim myid

The other two servers are numbered 2 and 3, respectively.

At this point, the configuration is complete, and then we start the zookeeper service.

Run on three servers

[root@rocketmq-nameserver1 ~] # zkServer.sh start

View zookeeper service startup status

[root@rocketmq-nameserver1 ~] # zkServer.sh status

At this point, the zookeeper cluster has been built.

Here are the common commands for zookeeper

Conf: outputs the details of the relevant service configuration.

Cons: lists the full connection / session details of all clients connected to the server. Includes information about the number of packets "accepted / sent", session id, operation delay, last operation execution, and so on.

Dump: lists unhandled sessions and temporary nodes.

Envi: outputs detailed information about the service environment (different from the conf command).

Reqs: lists unprocessed requests

Ruok: test whether the service is in the correct state. If so, the service returns "imok", otherwise no response is made.

Stat: outputs a list of performance and connected clients.

Wchs: lists the details of the server watch.

Wchc: lists the details of the server watch through session, and its output is a list of watch-related sessions.

Wchp: lists the details of the server watch by path. It outputs a path related to session.

Zookeeper command line tool

Connect to the zookeeper service through zkCli.sh, as follows

[root@rocketmq-nameserver2 ~] # zkCli.sh-server 192.168.2.178VR 2181

After a successful connection, it will be shown in the following figure:

Here we can enter the zookeeper command to do the relevant operations. You can use help for help queries. Here are all the commands under the zookeeper command line

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

For the use of specific commands, please refer to the official documentation, which is not described too much here.

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