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Posted to commits@cassandra.apache.org by "Benedict (JIRA)" <ji...@apache.org> on 2018/09/20 21:59:00 UTC
[jira] [Comment Edited] (CASSANDRA-14771) Transient Replication:
Writes at CL.ALL should block on all full replicas, but not transients
[ https://issues.apache.org/jira/browse/CASSANDRA-14771?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16622772#comment-16622772 ]
Benedict edited comment on CASSANDRA-14771 at 9/20/18 9:58 PM:
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Just for clarity of future readers, per CASSANDRA-14768, we might still want to *write* to transient nodes if, due to timeouts on writes to full nodes, we fail to reach {{QUORUM}} in any given DC. But we wouldn't pick any upfront since we'd fail with unavailable if we can't find enough full to write to, would not *rapid write protection* to them, and would not block our response on them.
Probably this can fairly easily be implemented by narrowing the candidates set to only the full replicas to prevent speculation, and using a simple {{AbstractWriteResponseHandler}} with {{blockFor}} set to the full node count.
was (Author: benedict):
Just for clarity of future readers, per CASSANDRA-14768, we might still want to *write* to transient nodes if, due to timeouts on writes to full nodes, we fail to reach {{QUORUM}} in any given DC. But we wouldn't pick any upfront since we'd fail with unavailable if we can't find enough full to write to, would not *speculate* to them, and would not block our response on them.
Probably this can fairly easily be implemented by narrowing the candidates set to only the full replicas to prevent speculation, and using a simple {{AbstractWriteResponseHandler}} with {{blockFor}} set to the full node count.
> Transient Replication: Writes at CL.ALL should block on all full replicas, but not transients
> ----------------------------------------------------------------------------------------------
>
> Key: CASSANDRA-14771
> URL: https://issues.apache.org/jira/browse/CASSANDRA-14771
> Project: Cassandra
> Issue Type: Bug
> Components: Coordination
> Reporter: Ariel Weisberg
> Priority: Major
> Fix For: 4.0
>
>
> Reading at ONE will still be safe because ONE only selects full replicas. There is no reason to write to transients if we are going to block on all full replicas.
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