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Paulo Motta commented on CASSANDRA-13299: ----------------------------------------- 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. -- This message was sent by Atlassian JIRA (v6.4.14#64029) --------------------------------------------------------------------- To unsubscribe, e-mail: commits-unsubscr...@cassandra.apache.org For additional commands, e-mail: commits-h...@cassandra.apache.org