Enable Admin Server in Zookeeper

Admin Server

Zookeeper is proving embedded jetty container to provide HTTP interface to execute commands. From Zookeeper 3.5.0 onwards HTTP interface is available. We need to enabled the Admin server from zookeeper configuration.

 

Zookeeper is providing set of 4 letters commands to manage and see the information of the servers and these commands can be executed from telenet. The same commands we can also execute via HTTP interface when we enabled Admin server in Zookeeper.

 

Zookeeper Commands

conf   New in 3.3.0: Print details about serving configuration.   cons   New in 3.3.0: List full connection/session details for all clients connected to this server. Includes information on numbers of packets received/sent, session id, operation latencies, last operation performed, etc…   crst   New in 3.3.0: Reset connection/session statistics for all connections.   dump   Lists the outstanding sessions and ephemeral nodes. This only works on the leader.   envi   Print details about serving environment   ruok   Tests if server is running in a non-error state. The server will respond with imok if it is running. Otherwise, it will not respond at all.   A response of "imok" does not necessarily indicate that the server has joined the quorum, just that the server process is active and bound to the specified client port. Use "stat" for details on state wrt quorum and client connection information.   srst   Reset server statistics.   srvr   New in 3.3.0: Lists full details for the server.   stat   Lists brief details for the server and connected clients.   wchs   New in 3.3.0: Lists brief information on watches for the server.   wchc   New in 3.3.0: Lists detailed information on watches for the server, by session. This outputs a list of sessions(connections) with associated watches (paths). Note, depending on the number of watches this operation may be expensive (ie impact server performance), use it carefully.   wchp   New in 3.3.0: Lists detailed information on watches for the server, by path. This outputs a list of paths (znodes) with associated sessions. Note, depending on the number of watches this operation may be expensive (ie impact server performance), use it carefully.   mntr   New in 3.4.0: Outputs a list of variables that could be used for monitoring the health of the cluster.

 

 

Prerequisite

Setup a Zookeeper cluster

 

http://www.liferaysavvy.com/2021/07/setup-zookeeper-cluster.html

 

Configure Admin Server

We need to update following properties in “zoo.cfg” for each node in the cluster.

Zookeeper Node 1

admin.enableServer=true admin.serverPort=9191

 

Zookeeper Node 2

admin.enableServer=true admin.serverPort=9292

 

Zookeeper Node 3

admin.enableServer=true admin.serverPort=9393

 

Restart All zookeeper nodes in the cluster and access following URLs to see the commands interface.

 

Zookeeper Node 1

 

http://localhost:9191/commands

 

Click on each hyper link to execute command and we can see JSON response.

Examples

To see the leader in the cluster

http://localhost:9191/commands/leader

 

Stats of the server

http://localhost:9191/commands/stats

Similarly, you can access server HTTP interface for other nodes from following URL’s

 

Zookeeper Node2

http://localhost:9292/commands

 

 

Zookeeper Node3

http://localhost:9393/commands

 

References

https://zookeeper.apache.org/doc/r3.5.1-alpha/zookeeperAdmin.html

 

 

Author

Meera Prince

Liferay Contributor of the Year 2016
Liferay Top Contributor Award Winner 2015

Liferay Contributor of the Year 2014

Liferay Top Contributor Award Winner 2013

http://www.liferaysavvy.com 

 

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Setup a Zookeeper Cluster

Apache Zookeeper is distributed coordination service to build distributed applications. Kafka uses the Zookeeper to manage cluster.

Kafka is included with Zookeeper and we can start as service however we can also install standalone zookeeper. This article demonstrates the setting up zookeeper cluster.

 

Prerequisite

Latest Zookeeper is required minimum JAVA version 1.8 and above (JAVA_HOME environment variable need setup in the system)

 

Need 7zip software to extract .tgz files in windows.

 

Software's and Tools

Windows 10 Java 1.8 or higher Zookeeper 3.7.0

 

 

Download and Extract

Download latest zookeeper binary tar.gz from following apache zookeeper download page.

 

https://zookeeper.apache.org/releases.html

 

Direct link as follow

 

https://www.apache.org/dyn/closer.lua/zookeeper/zookeeper-3.7.0/apache-zookeeper-3.7.0-bin.tar.gz

 

Extract downloaded “apache-zookeeper-3.7.0-bin.tar.gz” using 7z software in local drive. We are going to setup 3 node cluster so clone extracted directory 2 more times.

 

Name the directories as follows

zookeeper-node1 zookeeper-node2 zookeeper-node3

 

 

Configure Cluster

Zookeeper Node1

Step:1

Data Directory

Create data directory in “zookeeper-node1” and we will use this directory path in zookeeper configuration.

Example:

C:\\kafka-workspace\\zookeeper-node1\\data

 

 

 

Step:2

Create “myid” file

We need to create “myid” file in data directory and update file name with node number that is “1”.

Step:3

Zookeeper Configuration

Now have to update few zookeeper configuration properties. Go to zookeeper-node1 directory and rename “zoo_sample.cfg” to “zoo.cfg”

 

 

 

Add/Update “zoo.cfg” file with following properties.

 

clientPort=2181 dataDir=C:\\kafka-workspace\\zookeeper-node1\\data   autopurge.snapRetainCount=3 autopurge.purgeInterval=24   server.1=localhost:2666:3666 server.2=localhost:2667:3667 server.3=localhost:2668:3668   tickTime=2000 initLimit=10 syncLimit=5

 

 

server.<myid>=<hostname>:<leaderport>:<electionport>

 

We are setting up 3 node cluster so we have to configure server.[myid] property which have host name, leader and elector ports. Zookeeper use this information to form cluster.

Note:

we are using same machine to setup cluster so we have to make sure there is no port conflicts.

 

Zookeeper Node2 & Zookeeper Node2

Repeat Zookeeper Node1 Steps 1,2 and 3 for Zookeeper Node2 and Node3 and maintain unique port numbers.

 

Zookeeper Node2

myid file content is “2”

 

Add/Update “zoo.cfg” file with following properties.

 

clientPort=2182 dataDir=C:\\kafka-workspace\\zookeeper-node1\\data   autopurge.snapRetainCount=3 autopurge.purgeInterval=24   server.1=localhost:2666:3666 server.2=localhost:2667:3667 server.3=localhost:2668:3668   tickTime=2000 initLimit=10 syncLimit=5

 

Zookeeper Node3

myid file content is “3”

 

Add/Update “zoo.cfg” file with following properties.

 

clientPort=2183 dataDir=C:\\kafka-workspace\\zookeeper-node1\\data   autopurge.snapRetainCount=3 autopurge.purgeInterval=24   server.1=localhost:2666:3666 server.2=localhost:2667:3667 server.3=localhost:2668:3668   tickTime=2000 initLimit=10 syncLimit=5

 

Start Zookeeper Node 1,2 and 3

Zookeeper Node1

Open command prompt and locate to “zookeeper-node1” bin directory and use following command to start zookeeper server.

 

zkServer.cmd

 

 

Zookeeper console logs will give us the more details on server startup.

 

Note:

You may see “java.net.ConnectException: Connection refused: connect” warning and its due to other nodes are not yet started.

Zookeeper Node2

Open command prompt and locate to “zookeeper-node2” bin directory and use following command to start zookeeper server.

 

zkServer.cmd

 

Zookeeper Node3

 

Open command prompt and locate to “zookeeper-node3” bin directory and use following command to start zookeeper server.

 

zkServer.cmd

 

In the cluster only one node will be leader and other all nodes are followers. Leader and follower’s information can be view in the logs.

 

Node1( Leader)

Node2 (Follower)

Node3 (Follower)

 

Now successfully configured zookeeper cluster on windows.

References

https://zookeeper.apache.org/doc/current/index.html

Author

Meera Prince

Liferay Contributor of the Year 2016
Liferay Top Contributor Award Winner 2015

Liferay Contributor of the Year 2014

Liferay Top Contributor Award Winner 2013

http://www.liferaysavvy.com 

Read More