[
https://issues.apache.org/jira/browse/HDDS-4308?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17211254#comment-17211254
]
Bharat Viswanadham commented on HDDS-4308:
------------------------------------------
As mentioned in the scenario this can happen when double buffer flush is not
completed and other transaction requests updating bytes used for the same key.
When you run with a load this can be seen, as previously we have observed
ConcurrentModificatinException because of using the same cache object in the
double buffer. HDDS-2322
But here we might not see an error, but here this can happen bytesUsed will be
updated wrongly.
Coming to the solution, I think we can use read lock and acquire volume Object
using Table#get API and update bytes used and submit this object to double
buffer. (In this way, we might not see volume lock contention, as we acquire
write lock on volume during create/delete, so this might no affect performance.
Let me know your thoughts?
> Fix issue with quota update
> ---------------------------
>
> Key: HDDS-4308
> URL: https://issues.apache.org/jira/browse/HDDS-4308
> Project: Hadoop Distributed Data Store
> Issue Type: Bug
> Reporter: Bharat Viswanadham
> Priority: Blocker
>
> Currently volumeArgs using getCacheValue and put the same object in
> doubleBuffer, this might cause issue.
> Let's take the below scenario:
> InitialVolumeArgs quotaBytes -> 10000
> 1. T1 -> Update VolumeArgs, and subtracting 1000 and put this updated
> volumeArgs to DoubleBuffer.
> 2. T2-> Update VolumeArgs, and subtracting 2000 and has not still updated to
> double buffer.
> *Now at the end of flushing these transactions, our DB should have 7000 as
> bytes used.*
> Now T1 is picked by double Buffer and when it commits, and as it uses cached
> Object put into doubleBuffer, it flushes to DB with the updated value from
> T2(As it is a cache object) and update DB with bytesUsed as 7000.
> And now OM has restarted, and only DB has transactions till T1. (We get this
> info from TransactionInfo
> Table(https://issues.apache.org/jira/browse/HDDS-3685)
> Now T2 is again replayed, as it is not committed to DB, now DB will be again
> subtracted with 2000, and now DB will have 5000.
> But after T2, the value should be 7000, so we have DB in an incorrect state.
> Issue here:
> 1. As we use a cached object and put the same cached object into double
> buffer this can cause this kind of issue.
--
This message was sent by Atlassian Jira
(v8.3.4#803005)
---------------------------------------------------------------------
To unsubscribe, e-mail: ozone-issues-unsubscr...@hadoop.apache.org
For additional commands, e-mail: ozone-issues-h...@hadoop.apache.org
