Friday, July 9, 2021

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

 

 

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