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https://issues.apache.org/jira/browse/CASSANDRA-414?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12751624#action_12751624
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Jonathan Ellis commented on CASSANDRA-414:
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when compaction completes it modifies CFS.sstables_ as follows:
- sstables_.put(new compacted sstable)
- remove the source sstables & delete their file on disk
now, NonBlockingHashMap guarantees that "Iterators and Enumerations return
elements reflecting the state of the hash table at some point at or since the
creation of the iterator/enumeration." BUT this has no effect on other parts
of the system, particularly the delete!
so the fundamental problem exhibeted by the unit tests is this:
- thread A starts iterating over sstables_
- compaction thread finishes and does its thing. now some of the files A
needs to see a consistent view of the data are gone: the set of sstables being
iterated over was in fact consistent but because we're violating encapsulation
by doing the delete and remove separately, we can get incorrect results.
I think the simplest solution is to use pseudo-finalizers to do the actual file
delete once no references to the owning SSTableReader exist anymore. These can
be done using
http://java.sun.com/javase/6/docs/api/java/lang/ref/ReferenceQueue.html and
http://java.sun.com/javase/6/docs/api/java/lang/ref/PhantomReference.html.
> remove sstableLock
> ------------------
>
> Key: CASSANDRA-414
> URL: https://issues.apache.org/jira/browse/CASSANDRA-414
> Project: Cassandra
> Issue Type: Improvement
> Components: Core
> Reporter: Jonathan Ellis
> Assignee: Jonathan Ellis
> Fix For: 0.5
>
> Attachments:
> 0001-CASSANDRA-414-combine-addToList-and-storeLocation-ren.txt,
> 0001-CASSANDRA-414-combine-addToList-and-storeLocation-ren.txt,
> 0002-remove-sstableLock.-re-order-a-few-ops-so-that-we-can.txt,
> 0002-remove-sstableLock.-re-order-a-few-ops-so-that-we-can.txt
>
>
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