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https://issues.apache.org/jira/browse/CASSANDRA-13299?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16166039#comment-16166039
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Paulo Motta edited comment on CASSANDRA-13299 at 9/14/17 10:08 AM:
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Thanks, the patch looks good from an initial look, great job! Some minor
comments:
* Generalize {{ThrottledUnfilteredIterator}} since it can also be useful
outside of streaming package:
** Make {{ThrottledUnfilteredIterator}} an {{Iterator<UnfilteredRowIterator>}}
instead of using {{hasNextGroup}} and {{resetLimit}} which is analogous to
{{hasNext}} and {{next}}.
** Move to {{org.apache.cassandra.db.rows}} package
** Add simple javadoc explaining what it does
** Move {{cassandra.mv.mutation.row.count}} out of
{{ThrottledUnfilteredIterator}}, and maybe rename it to
{{cassandra.repair.mutation_repair_rows_per_batch}} (or similar, since it's
also used for CDC).
* Add unit test to {{ThrottledUnfilteredIterator}} to make sure it's generating
range tombstones correctly
dtest looks good!
was (Author: pauloricardomg):
Thanks, the patch looks good from an initial look, great job! Some minor
comments:
* Generalize {{ThrottledUnfilteredIterator}} since it can also be useful
outside of streaming package:
** Make {{ThrottledUnfilteredIterator}} an {{Iterator<UnfilteredRowIterator>}}
instead of using {{hasNextGroup}} and {{resetLimit}} which is analogous to
{{hasNext}} and {{next}}.
** Move to {{org.apache.cassandra.db.rows}} package
** Add simple javadoc explaining what it does
** Move {{cassandra.mv.mutation.row.count}} out of
{{ThrottledUnfilteredIterator}}, and maybe rename it to
{{cassandra.repair.mutation_repair_rows_per_batch}} (or similar, since it's
also used for CDC).
* Add unit test to {{ThrottledUnfilteredIterator}} to make sure it's generating
range tombstones correctly
> Potential OOMs and lock contention in write path streams
> --------------------------------------------------------
>
> Key: CASSANDRA-13299
> URL: https://issues.apache.org/jira/browse/CASSANDRA-13299
> Project: Cassandra
> Issue Type: Improvement
> Reporter: Benjamin Roth
> Assignee: ZhaoYang
>
> I see a potential OOM, when a stream (e.g. repair) goes through the write
> path as it is with MVs.
> StreamReceiveTask gets a bunch of SSTableReaders. These produce rowiterators
> and they again produce mutations. So every partition creates a single
> mutation, which in case of (very) big partitions can result in (very) big
> mutations. Those are created on heap and stay there until they finished
> processing.
> I don't think it is necessary to create a single mutation for each partition.
> Why don't we implement a PartitionUpdateGeneratorIterator that takes a
> UnfilteredRowIterator and a max size and spits out PartitionUpdates to be
> used to create and apply mutations?
> The max size should be something like min(reasonable_absolute_max_size,
> max_mutation_size, commitlog_segment_size / 2). reasonable_absolute_max_size
> could be like 16M or sth.
> A mutation shouldn't be too large as it also affects MV partition locking.
> The longer a MV partition is locked during a stream, the higher chances are
> that WTE's occur during streams.
> I could also imagine that a max number of updates per mutation regardless of
> size in bytes could make sense to avoid lock contention.
> Love to get feedback and suggestions, incl. naming suggestions.
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