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https://issues.apache.org/jira/browse/CASSANDRA-2034?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13085497#comment-13085497
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Jonathan Ellis commented on CASSANDRA-2034:
-------------------------------------------
Hmm. I think you're right: it would work better to do the hints in the handler
instead of passing these lists around. Sorry; let's change it to do it that
way.
Other notes:
SP.shouldHint is broken (will always return true when hints are disabled). I
would write it like this:
{code}
public static boolean shouldHint(InetAddress ep)
{
if (!isHintedHandoffEnabled())
return false;
boolean hintWindowExpired = Gossiper.instance.getEndpointDowntime(ep) >
maxHintWindow;
if (hintWindowExpired)
logger.debug("not hinting {} which has been down {}ms", ep,
Gossiper.instance.getEndpointDowntime(ep));
return !hintWindowExpired;
}
{code}
CallbackInfo.shouldHint is broken a different way. It should be returning true
if and only if the write to the target failed. (Calling this variable "from"
is odd -- "from" is used to refer to localhost in a MessageService context.)
Currently, it returns true if the overall CL is achieved, which in the general
case tells us nothing about the individual replica in question.
> Make Read Repair unnecessary when Hinted Handoff is enabled
> -----------------------------------------------------------
>
> Key: CASSANDRA-2034
> URL: https://issues.apache.org/jira/browse/CASSANDRA-2034
> Project: Cassandra
> Issue Type: Improvement
> Components: Core
> Reporter: Jonathan Ellis
> Assignee: Patricio Echague
> Fix For: 1.0
>
> Attachments: 2034-formatting.txt, CASSANDRA-2034-trunk-v10.patch,
> CASSANDRA-2034-trunk-v11.patch, CASSANDRA-2034-trunk-v11.patch,
> CASSANDRA-2034-trunk-v12.patch, CASSANDRA-2034-trunk-v13.patch,
> CASSANDRA-2034-trunk-v14.patch, CASSANDRA-2034-trunk-v2.patch,
> CASSANDRA-2034-trunk-v3.patch, CASSANDRA-2034-trunk-v4.patch,
> CASSANDRA-2034-trunk-v5.patch, CASSANDRA-2034-trunk-v6.patch,
> CASSANDRA-2034-trunk-v7.patch, CASSANDRA-2034-trunk-v8.patch,
> CASSANDRA-2034-trunk-v9.patch, CASSANDRA-2034-trunk.patch
>
> Original Estimate: 8h
> Remaining Estimate: 8h
>
> Currently, HH is purely an optimization -- if a machine goes down, enabling
> HH means RR/AES will have less work to do, but you can't disable RR entirely
> in most situations since HH doesn't kick in until the FailureDetector does.
> Let's add a scheduled task to the mutate path, such that we return to the
> client normally after ConsistencyLevel is achieved, but after RpcTimeout we
> check the responseHandler write acks and write local hints for any missing
> targets.
> This would making disabling RR when HH is enabled a much more reasonable
> option, which has a huge impact on read throughput.
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