CODEWITHSUNDEEP
apache-zookeeper
Daniel C. Sobral
Daniel C. Sobral

Reputation: 297205

Going from a single zookeeper server to a clustered configuration

I have a single server that I now want to replicate and go for higher availability. One of the elements in my software stack if Zookeeper, so it seems natural to go to a clustered configuration on it.

However, I have data on my single server, and I couldn't find any guide on going to a clustered setup. I tried setting up two independent instances and then going to a clustered configuration, but only data present on the elected master was preserved.

So, how can I safely go from a single server setup to a clustered setup without losing data?

Upvotes: 4

Views: 426

Answers (1)

sbridges
sbridges

Reputation: 25150

If you go from 1 server straight to 3 servers, you may lose data, as the 2 new servers are sufficient to form a quorum, and elect one of themselves as a leader, ignoring the old server, and losing all data on that machine.

If you grow your cluster from 1 to 2, when the two servers start up, then a quorum can't form without the old server being involved, and data will not be lost. When the cluster finishes starting, all data will be synced to both servers.

Then you can grow your cluster from 2 to 3, and again a quorum can't form without at least 1 server that has a copy of the database, and again when the cluster finishes starting all data will be synced to all three servers.

Upvotes: 2

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