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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.
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It's basically the minimum number of server nodes that must be up and running and available for client requests. Any update done to the ZooKeeper tree by the clients must be persistently stored in this quorum of nodes for a transaction to be completed successfully.
If one the ZooKeeper nodes fails, the following occurs: Other ZooKeeper nodes detect the failure to respond. A new ZooKeeper leader is elected if the failed node is the current leader. If multiple nodes fail and ZooKeeper loses its quorum, it will drop into read-only mode and reject requests for changes.
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.
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
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