[jira] [Commented] (CASSANDRA-12671) Support changing hinted handoff throttle in real time

["Aleksey Yeschenko (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CASSANDRA-12671?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15721721#comment-15721721 ] 

Aleksey Yeschenko commented on CASSANDRA-12671:
-----------------------------------------------

Sorry, but I don't think this particular implementation will do.

1. {{getHintedHandoffThrottleBytesPerNode()}} does not belong to {{DatabaseDescriptor}}. That class should be kept as close to a dumb wrapper over {{Config}} as possible.

2. That calculation is not cheap, and as such should not be performed on *every hint read*. Hint:

{code}
    public Set<InetAddress> getAllEndpoints()
    {
        lock.readLock().lock();
        try
        {
            return ImmutableSet.copyOf(endpointToHostIdMap.keySet());
        }
        finally
        {
            lock.readLock().unlock();
        }
    }
{code}

Generally I would recommend reading the source code of every method you call, to know what each of them does under the hood. Can't always move code from one place to another: what's acceptable as a one-off call might not be acceptable on a hot path.

3. How are you even updating {{conf.hinted_handoff_throttle_in_kb}} live? Am I missing something? Are you using a custom configuration provider?

4. Either way, this change, I assume, is not a frequent event. As such changes to the rate limit should be push-based, not pull-based.

> Support changing hinted handoff throttle in real time 
> ------------------------------------------------------
>
>                 Key: CASSANDRA-12671
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-12671
>             Project: Cassandra
>          Issue Type: Improvement
>            Reporter: Dikang Gu
>            Assignee: Dikang Gu
>            Priority: Minor
>             Fix For: 3.x
>
>
> Problem: currently the sethintedhandoffthrottlekb takes effect when current hints handoff tasks finish, and then applies to next task, which could take hours for big node. 
> I think it would be great to change the hinted handoff throttle in real time, which means it takes effect immediately. 



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