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https://issues.apache.org/jira/browse/SOLR-17102?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17871540#comment-17871540
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ASF subversion and git services commented on SOLR-17102:
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Commit 69f180933b2c968dda24a014bfe01b74e2eebd8b in solr's branch
refs/heads/branch_9x from David Smiley
[ https://gitbox.apache.org/repos/asf?p=solr.git;h=69f180933b2 ]
SOLR-17102: Replaced VersionBucket array with locks on-demand (#2548)
The VersionBucket indexing lock mechanism was replaced with something just as
fast yet that which consumes almost no memory, saving 1MB of memory per
SolrCore.
Removed numVersionBuckets and versionBucketLockTimeoutMs.
Refactorings:
DistributedUpdateProcessor: some refactoring to balance locks clearly.
VersionInfo: moved locks out to new UpdateLocks.
OrderedExecutor uses generics now. Allows use of the ID directly (a BytesRef)
instead of a hash.
(cherry picked from commit 7ccf4d3c9af7a03dc5ffce8cceda11c360fbccd0)
> VersionBucket not needed
> ------------------------
>
> Key: SOLR-17102
> URL: https://issues.apache.org/jira/browse/SOLR-17102
> Project: Solr
> Issue Type: Improvement
> Components: SolrCloud
> Reporter: David Smiley
> Assignee: David Smiley
> Priority: Major
> Labels: pull-request-available
> Time Spent: 2h 50m
> Remaining Estimate: 0h
>
> SolrCloud ensures that updates for the same document ID are done in the
> correct order internally in the face of possible re-orders during replication
> / log replay. In order to ensure the updates are applied consecutively, a
> lock is held on a hash of the ID for the doc. A hash is used to limit the
> number of total locks because the locks are pre-created in advance for the
> core (numVersionBuckets == 65k by default). The memory is non-negligible
> with many cores, and it introduces the possibility of collisions, especially
> at lower bucket counts if you configure it much lower.
> Here I propose doing away with a pre-created hashed bucket strategy.
> Instead, I propose more simply creating and GC'ing a lock per update being
> processed, and using a ConcurrentHashMap to hold those in-flight. This
> strategy is already used in
> org.apache.solr.util.OrderedExecutor.SparseStripedLock, more or less.
> Doing this is more tractable now that VersionBucket only holds a lock, not a
> version anymore – SOLR-17036
> The biggest challenge is that the code calls for the ability to use a
> Condition to away/notify, which means the solution can't just re-use
> SparseStripedLock above nor be quite so simple.
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