etcd : how does etcd handle 'write to follower'?

[Gyu-Ho Lee]

Hello, I am new to raft and etcd. 

Here https://www.youtube.com/watch?v=YbZ3zDzDnrw

Diego Ongaro explains that it's fine for a client to send requests to followers

, given that the client does not know which machine is the leader.

And just returns telling back the client which is the leader.

I deployed a cluster of 3 etcd machines

, assuming that all RPC could be done with simple cURL commands.

And the client is not expected to know which machine is the leader.

For this case, would it be ok to POST request to any of those 3 machines?

Or do I have to tell them to use etcd-client, where you can specify the 3 machines endpoints.

If it's ok to post requests to any machine, even if it might not be the leader,

how does etcd handle this and point this request to leader node?

Or do I misunderstand the raft algorithm?

Could anybody help me find the related code in etcd repo?

Thanks!

[Brandon Philips]

Hello Gyu-Ho-

Yes, a client can submit a write request to any machine in the cluster. What happens is the etcd machine you contact creates a raft RPC and tags it with a unique id. When the machine sees that unique id tag come back as a raft log commit then it returns a 200 OK to the client.

Does that make sense? If you have more technical questions about etcd I would suggest you email etcd-dev instead. https://groups.google.com/forum/#!forum/etcd-dev

Thank You,

Brandon

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[Gyu-Ho Lee]

I see. That makes sense. Thanks for clarification. And I will go to the etcd mailing list next time. Thanks!

Sincerely,

Gyu-Ho Lee