How to validate zookeeper quorum

Question

How do I verify that all the nodes in a zookeeper are part of a quorum and are healthy? Manual talks about "ruok" but that doesnt still say if the zookeeper node is part of quorum and is in sync with the rest.

Hibbitts

Answer 1

You can use the srvr command documented in The Four Letter Words to get more detailed status information about each ZooKeeper server in the ensemble. See below for sample output from a 3-node cluster, with hosts named ubuntu1, ubuntu2 and ubuntu3.

The Mode field will tell you if that particular server is the leader or a follower. The Zxid field refers to the ZooKeeper cluster's internal transaction ID used for tracking state changes to the tree of znodes. In a healthy cluster, you'll see one leader, multiple followers, and all nodes will generally be close to one another in the zxid value.

> for x in ubuntu1 ubuntu2 ubuntu3; do echo $x; echo srvr|nc $x 2181; echo; done
ubuntu1
Zookeeper version: 3.4.7-1713338, built on 11/09/2015 04:32 GMT
Latency min/avg/max: 3/9/21
Received: 9
Sent: 8
Connections: 1
Outstanding: 0
Zxid: 0x100000004
Mode: follower
Node count: 6

ubuntu2
Zookeeper version: 3.4.7-1713338, built on 11/09/2015 04:32 GMT
Latency min/avg/max: 0/0/0
Received: 2
Sent: 1
Connections: 1
Outstanding: 0
Zxid: 0x100000004
Mode: leader
Node count: 6

ubuntu3
Zookeeper version: 3.4.7-1713338, built on 11/09/2015 04:32 GMT
Latency min/avg/max: 0/0/0
Received: 2
Sent: 1
Connections: 1
Outstanding: 0
Zxid: 0x100000004
Mode: follower
Node count: 6

Periwig