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https://issues.apache.org/jira/browse/CASSANDRA-3199?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Jonathan Ellis resolved CASSANDRA-3199.
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Resolution: Won't Fix
> Counter write protocol: have the coordinator (instead of first replica) waits
> for replica responses directly
> ------------------------------------------------------------------------------------------------------------
>
> Key: CASSANDRA-3199
> URL: https://issues.apache.org/jira/browse/CASSANDRA-3199
> Project: Cassandra
> Issue Type: Improvement
> Components: Core
> Reporter: Sylvain Lebresne
> Priority: Minor
> Labels: counters
>
> Current counter write protocol is this (where we take the case of write
> coordinator != first replica):
> # coordinator forward write request to first replica
> # first replica write locally and replicate to other replica
> # first replica waits for enough answers from the other replica to satisfy
> the consistency level
> # first replica acks the coordinator that completes the write to the client
> This ticket proposes to modify this protocol to:
> # coordinator forward write request to first replica
> # first replica write locally, acks the coordinator for its own write and
> replicate to other replica
> # other replica respond directly to coordinator
> # once coordinator has enough responses, it completes the write
> I see 2 advantages to this new protocol:
> * it should be at tad faster since it parallelizes wire transfer better
> * it woud make TimeoutException a bit less likely and more importantly, a
> TimeoutException would much more likely mean that the write hasn't been
> persisted. Indeed, in the current protocol, once the first replica has send
> the write to the other replica, it has to wait for the replica answers and
> answer the coordinator. If it dies during that time, we will return a
> TimeoutException, even though the first replica died after having done it's
> main job.
> The cons is that this adds a bit of complexity. In particular, the "other
> replica" would have to answer to the coordinator for a query that has been
> issued by the first replica.
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