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