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https://issues.apache.org/jira/browse/CASSANDRA-13074?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Joel Knighton updated CASSANDRA-13074:
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Status: Patch Available (was: Open)
||branch||testall||dtest||
|[des-snitch-changes-2.2|https://github.com/jkni/cassandra/tree/des-snitch-changes-2.2]|[testall|http://cassci.datastax.com/view/Dev/view/jkni/job/jkni-des-snitch-changes-2.2-testall]|[dtest|http://cassci.datastax.com/view/Dev/view/jkni/job/jkni-des-snitch-changes-2.2-dtest]|
|[des-changes-3.0|https://github.com/jkni/cassandra/tree/des-changes-3.0]|[testall|http://cassci.datastax.com/view/Dev/view/jkni/job/jkni-des-changes-3.0-testall]|[dtest|http://cassci.datastax.com/view/Dev/view/jkni/job/jkni-des-changes-3.0-dtest]|
|[des-changes-3.11|https://github.com/jkni/cassandra/tree/des-changes-3.11]|[testall|http://cassci.datastax.com/view/Dev/view/jkni/job/jkni-des-changes-3.11-testall]|[dtest|http://cassci.datastax.com/view/Dev/view/jkni/job/jkni-des-changes-3.11-dtest]|
|[des-changes-3.X|https://github.com/jkni/cassandra/tree/des-changes-3.X]|[testall|http://cassci.datastax.com/view/Dev/view/jkni/job/jkni-des-changes-3.X-testall]|[dtest|http://cassci.datastax.com/view/Dev/view/jkni/job/jkni-des-changes-3.X-dtest]|
|[des-changes-trunk|https://github.com/jkni/cassandra/tree/des-changes-trunk]|[testall|http://cassci.datastax.com/view/Dev/view/jkni/job/jkni-des-changes-trunk-testall]|[dtest|http://cassci.datastax.com/view/Dev/view/jkni/job/jkni-des-changes-trunk-dtest]|
I've attached all branches, but the merge forward from 2.2 is clean except for
a trivial to resolve merge conflict in 3.0 -> 3.11. CI looks clean.
Although the patch is small, there's a fair amount of nuance here. We no longer
want to seed with a latency of zero - in this case, if you're doing lots of
local_quorum reads or something similar, populating with zero would mean that
we no longer get any benefits from stickiness. With this patch, we only
populate with real latencies.
> DynamicEndpointSnitch frequently no-ops through early exit in
> multi-datacenter situations
> -----------------------------------------------------------------------------------------
>
> Key: CASSANDRA-13074
> URL: https://issues.apache.org/jira/browse/CASSANDRA-13074
> Project: Cassandra
> Issue Type: Bug
> Components: Coordination
> Reporter: Joel Knighton
> Assignee: Joel Knighton
> Fix For: 2.2.x, 3.0.x, 3.x, 4.x
>
>
> The DynamicEndpointSnitch attempts to use timings from nodes to route reads
> to better performing nodes.
> In a multi-datacenter situation, timings will likely be empty for nodes
> outside of the local datacenter, as you'll frequently only be doing
> local_quorum reads (or a lower consistency level). In this case, the DES
> exits early and returns the subsnitch ordering. This means poorly performing
> replicas will never be avoided, no matter how degraded they are.
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