Non-blocking DataRowStore
-------------------------
Key: CAY-1670
URL: https://issues.apache.org/jira/browse/CAY-1670
Project: Cayenne
Issue Type: Improvement
Components: Core Library
Affects Versions: 3.1M3
Reporter: Andrus Adamchik
Assignee: Andrus Adamchik
Until we decide on unifying object and query caches, it would be cool if we
could remove the shared lock from DataRowStore that causes issues like
CAY-1124, and generally creates contention on access from multiple threads.
We would need some kind of cross-over between LinkedHashMap (that allows to set
up LRU policies among other things) and ConcurrentHashMap. There are a few
solutions out there that may provide needed characteristics:
1. http://code.google.com/p/concurrentlinkedhashmap/ (the quality is unclear)
2. Guava MapMaker
http://guava-libraries.googlecode.com/svn/trunk/javadoc/com/google/common/collect/MapMaker.html
(is it based on #1?)
#2 will require a huge 1.7MB Guava lib as a dependency for Cayenne. So maybe
experiment with #1...
3. Also was thinking of useing JDK ConcurrentHashMap, and implementing a FIFO
eviction mechanism instead of LRU. FIFO should be easier to implement in our
code. This change has a chance to cause havoc in Cayenne though (snapshots just
loaded would get kicked out within the same transaction).
Another issue which is agnostic to whatever implementation we'd chose, is what
happens when certain operations become non-atomic when we remove synchronized
blocks:
synchronized (this) {
processDeletedIDs(deletedSnapshotIds);
processInvalidatedIDs(invalidatedSnapshotIds);
processUpdateDiffs(diffs);
sendUpdateNotification(
event.getPostedBy(),
diffs,
deletedSnapshotIds,
invalidatedSnapshotIds,
indirectlyModifiedIds);
}
Anyways this will require some research and testing.
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