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https://issues.apache.org/jira/browse/IGNITE-11704?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16946165#comment-16946165
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Alexei Scherbakov commented on IGNITE-11704:
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[~jokser] [~sboikov]
I've reviewed changes. Overall looks good, but still I have some questions.
1. My main concern is regarding the necessity of tombstoneBytes 5-bytes object.
Seems it's possible to implement tombstone by treating absence of value as a
tombstone.
For example, valLen=0 could be treated as tombstone presense. Doing so we can
get rid of 5 bytes comparison, and instead do null check:
{noformat}
private Boolean isTombstone(ByteBuffer buf, int offset) {
int valLen = buf.getInt(buf.position() + offset);
if (valLen != tombstoneBytes.length)
return Boolean.FALSE;
...
}
{noformat}
Instead we can do something like {{if (valLen == 0) return true}}
2. With new changes in PartitionsEvictManager it's possible to have two tasks
of different types for the same partition.
Consider a scenario:
* node finished rebalancing and starts to clear thombstones
* another node joins topology and become an owner for clearing partition.
* eviction is started for already clearing partition.
Probably this should not be allowed.
3. I see changes having no obvious relation to contribution, for example:
static String cacheGroupMetricsRegistryName(String cacheGrp)
DropCacheContextDuringEvictionTest.java
GridCommandHandlerIndexingTest.java
What's the purpose of these ?
4. Could you explain the modification in
org.apache.ignite.internal.processors.cache.GridCacheMapEntry#initialValue:
update0 |= (!preload && val == null); ?
> Write tombstones during rebalance to get rid of deferred delete buffer
> ----------------------------------------------------------------------
>
> Key: IGNITE-11704
> URL: https://issues.apache.org/jira/browse/IGNITE-11704
> Project: Ignite
> Issue Type: Improvement
> Reporter: Alexey Goncharuk
> Assignee: Pavel Kovalenko
> Priority: Major
> Labels: rebalance
> Fix For: 2.8
>
> Time Spent: 10m
> Remaining Estimate: 0h
>
> Currently Ignite relies on deferred delete buffer in order to handle
> write-remove conflicts during rebalance. Given the limit size of the buffer,
> this approach is fundamentally flawed, especially in case when persistence is
> enabled.
> I suggest to extend the logic of data storage to be able to store key
> tombstones - to keep version for deleted entries. The tombstones will be
> stored when rebalance is in progress and should be cleaned up when rebalance
> is completed.
> Later this approach may be used to implement fast partition rebalance based
> on merkle trees (in this case, tombstones should be written on an incomplete
> baseline).
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