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https://issues.apache.org/jira/browse/IGNITE-13052?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Vladislav Pyatkov reassigned IGNITE-13052:
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Assignee: Vladislav Pyatkov
> Calculate result of reserveHistoryForExchange in advance
> --------------------------------------------------------
>
> Key: IGNITE-13052
> URL: https://issues.apache.org/jira/browse/IGNITE-13052
> Project: Ignite
> Issue Type: Improvement
> Reporter: Ivan Rakov
> Assignee: Vladislav Pyatkov
> Priority: Major
> Original Estimate: 80h
> Remaining Estimate: 80h
>
> Method reserveHistoryForExchange() is called on every partition map exchange.
> It's an expensive call: it requires iteration over the whole checkpoint
> history with possible retrieve of GroupState from WAL (it's stored on heap
> with SoftReference). On some deployments this operation can take several
> minutes.
> The idea of optimization is to calculate its result only on first PME
> (ideally, even before first PME, on recovery stage), keep resulting map
> (grpId, partId -> earlisetCheckpoint) on heap and update it if necessary.
> From the first glance, the map should be updated:
> 1) On checkpoint. If a new partition appears on local node, it should be
> registered in the map with current checkpoint. If a partition is evicted from
> local node, or changes its state to non-OWNING, it should be removed from the
> map. If checkpoint is marked as inapplicable for a certain group, the whole
> group should be removed from the map.
> 2) On checkpoint history cleanup. For every (grpId, partId), previous
> earliest checkpoint should be changed with setIfGreater to new earliest
> checkpoint.
> We should also extract WAL pointer reservation and filtering small partitions
> from reserveHistoryForExchange(), but this shouldn't be a problem.
> Another point for optimization: searchPartitionCounter() and
> searchCheckpointEntry() are executed for each (grpId, partId). That means
> we'll perform O(number of partitions) linear lookups in history. This should
> be optimized as well: we can perform one lookup for all (grpId, partId)
> pairs. This is especially critical for reserveHistoryForPreloading() method
> complexity: it's executed from exchange thread.
> Memory overhead of storing described map on heap is insignificant. Its size
> isn't greater than size of map returned from reserveHistoryForExchange().
> Described fix should be much simpler than IGNITE-12429.
> P.S. Possibly, instead of storing map, we can keep earliestCheckpoint right
> in GridDhtLocalPartition. It may simplify implementation.
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