How to check if ZooKeeper is running or up from command prompt?

Question

I exploring a few options to how Zookeeper is up and running

I would like to know how can I find the below.

1. hostname and port for my zookeeper instance---I checked the zoo.cfg and I could only find the ClientPort not the hostname, will hostname be the hostname of my box??

2. To check if ZooKeeper is up and running---I tried to do a ps -ef | grep "zoo" I could not find anything. May be I am using a wrong key word to search??

Any help would be really appreciated?

Wombat

Do you mean from the command prompt on zookeeper's node? or from the client node's command prompt? – Sicken

Answer 1

To check if Zookeeper is accessible. One method is to simply telnet to the proper port and execute the stats command.

root@host:~# telnet localhost 2181
Trying 127.0.0.1...
Connected to myhost.
Escape character is '^]'.
stats
Zookeeper version: 3.4.3-cdh4.0.1--1, built on 06/28/2012 23:59 GMT
Clients:

Latency min/avg/max: 0/0/677
Received: 4684478
Sent: 4687034
Outstanding: 0
Zxid: 0xb00187dd0
Mode: leader
Node count: 127182
Connection closed by foreign host.

Lindsey

telnet is often not available/installed on the servers – Massy

'stats' is not working on my Windows. Try 'srvr' instead. – Raft

The list of available "Four Letter Words" are listed here. According to this stat is the correct word. But - I think - it has to be whitelisted. In my case only srvr was whitelisted by default (windows). – Standby

Answer 2

One other way would be to use 4 letter commands to validate if zookeeper service is healthy or not

echo stat | nc <zookeeper ip> 2181
echo mntr | nc <zookeeper ip> 2181
echo isro  | nc <zookeeper ip> 2181

More details on the documentation link below https://zookeeper.apache.org/doc/r3.1.2/zookeeperAdmin.html#sc_zkCommands

Groundnut

echo ruok | nc <zookeeper ip> 2181 just returns "imok" if it is OK, so that is probably the easiest to parse. – Lozoya

nc might not be available in all environments. – Sicken

Don't forget to allow ZOO_4LW_COMMANDS_WHITELIST="*" or lesser e.g. "stat", if you're running Zk in a Container. Otherwise you'll get a stat is not executed because it is not in the whitelist. Reference – Guv

@JesseChisholm That goes without saying. There's a lot of popular commands that "might not be available in all environments," wget probably being the most common one despite often being used as the example by a huge amount of people to do web requests. Run a stripped down Docker image and even something as basic as the ip command might not be available. I've seen Ubuntu-based containers where sudo does not exist. It's really a moot point. – Ectoenzyme

Answer 3

Go to bin directory of Zookeeper and type

./zkServer.sh status

For More info go through below link:

http://www.ibm.com/developerworks/library/bd-zookeeper/

Hope this could help you.

Micturition

see: zookeeper.apache.org/doc/r3.4.8/zookeeperStarted.html and change "r3.4.8" to your zookeeper version – Vaudevillian

zkServer status ZooKeeper JMX enabled by default Using config: /usr/local/etc/zookeeper/zoo.cfg Mode: standalone – Relativistic

Link is no longer alive. Can't edit because the queue is full. – Underworld

Answer 4

echo stat | nc localhost 2181 | grep Mode
echo srvr | nc localhost 2181 | grep Mode #(From 3.3.0 onwards)

Above will work in whichever modes Zookeeper is running (standalone or embedded).

Another way

If zookeeper is running in standalone mode, its a JVM process. so -

jps | grep Quorum

will display list of jvm processes; something like this for zookeeper with process ID

HQuorumPeer

Isogamy

echo srvr | nc localhost 2181 | grep Mode worked for me – Cuffs

Answer 5

I did some test:

When it's running:

$ /usr/lib/zookeeper/bin/zkServer.sh status
JMX enabled by default
Using config: /usr/lib/zookeeper/bin/../conf/zoo.cfg
Mode: follower

When it's stopped:

$ zkServer status                                                                                                                                
JMX enabled by default
Using config: /usr/local/etc/zookeeper/zoo.cfg
Error contacting service. It is probably not running.

I'm not running on the same machine, but you get the idea.

Faria

Answer 6

enter the below command to verify if zookeeper is running :

echo "ruok" | nc localhost 2181 ; echo 

expected response: imok

Orlop

An instance may respond with "This ZooKeeper instance is not currently serving requests" to srvr command but still respond with "imok" to ruok command. – Hallett

Answer 7

Zookeeper is just a Java process and when you start a Zookeeper instance it runs a org.apache.zookeeper.server.quorum.QuorumPeerMain class. So you can check for a running Zookeeper like this:

jps -l | grep zookeeper

or even like this:

jps | grep Quorum

upd:

regarding this: will hostname be the hostname of my box?? - the answer is yes.

Millisent

Answer 8

From a Windows 10

• Open Command Promt then type telnet localhost 2181and then you type srvr OR
• From inside bin folder, open a PowerShell window and type zkServer.sh status

Stratus

Answer 9

I use:

  jps

Depending on your installation a running Zookeeper would look like

  HQuorumPeer

or sth. with zookeeper in it's name.

Quinquennial

Answer 10

For people who uses the official docker image:

https://hub.docker.com/_/zookeeper

in the whitelist is only enabled srvr

See below the example:

telnet hostname 2181                                                                                                                                
Trying ::1...
Connected to localhost.
Escape character is '^]'.
srvr
Zookeeper version: 3.7.0-e3704b390a6697bfdf4b0bef79e3da7a4f6bac4b, built on 2021-03-17 09:46 UTC
Latency min/avg/max: 0/0.0/0
Received: 3
Sent: 2
Connections: 1
Outstanding: 0
Zxid: 0x0
Mode: standalone
Node count: 5
Connection closed by foreign host.

Doc:

ZOO_4LW_COMMANDS_WHITELIST

Defaults to srvr. Zookeeper's 4lw.commands.whitelist

A list of comma separated Four Letter Words commands that user wants to use. A valid Four Letter Words command must be put in this list else ZooKeeper server will not enable the command. By default the whitelist only contains "srvr" command which zkServer.sh uses. The rest of four letter word commands are disabled by default.

Javier

Answer 11

For those of you who used homebrew, use this command - /opt/homebrew/Cellar/zookeeper/3.8.1/bin/zkServer status

Lotze

Answer 12

echo srvr|nc localhost 2181

It works when telnet is not installed and stat, mntr, ruok are not whitelisted.

Slipper