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https://issues.apache.org/jira/browse/CASSANDRA-17808?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Caleb Rackliffe updated CASSANDRA-17808:
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Change Category: Operability
Complexity: Normal
Component/s: Consistency/Hints
Fix Version/s: 4.x
Status: Open (was: Triage Needed)
> Optionally avoid hint transfer during decommission
> --------------------------------------------------
>
> Key: CASSANDRA-17808
> URL: https://issues.apache.org/jira/browse/CASSANDRA-17808
> Project: Cassandra
> Issue Type: Improvement
> Components: Consistency/Hints
> Reporter: Caleb Rackliffe
> Assignee: Caleb Rackliffe
> Priority: Normal
> Fix For: 4.x
>
>
> Both because they aren’t strictly necessary to maintain consistency, and
> because throttling induced by their rate-limiter (see
> {{hinted_handoff_throttle}}) may stall progress, transferring hints during
> decommission (specifically unbootstrap) rather than just pausing, disabling,
> and truncating them probably doesn’t make sense. The only other concern would
> be the BatchLog, which nominally depends on hint delivery to maintain its
> "guarantees". However, during BatchLog replay on unbootstrap,
> {{ReplayingBatch}} ignores batches older the gcgs anyway.
> Here's a proposal from [~aleksey] that might strike a reasonable balance:
> 1.) We continue to transfer hints by default during decommission, but at a
> higher rate. We could, for instance stop having {{DispatchHintsTask}} divide
> its effective rate by the number of nodes in the cluster.
> {noformat}
> int nodesCount = Math.max(1,
> StorageService.instance.getTokenMetadata().getAllEndpoints().size() - 1);
> double throttleInBytes =
> DatabaseDescriptor.getHintedHandoffThrottleInKiB() * 1024.0 / nodesCount;
> this.rateLimiter = RateLimiter.create(throttleInBytes == 0 ?
> Double.MAX_VALUE : throttleInBytes);
> {noformat}
> 2.) We provide an option to simply avoid transferring hints during
> unbootstrap. Even this would only take the BatchLog from "best effort" to
> "slightly less effort" ;)
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