mikemccand commented on a change in pull request #815: LUCENE-8213: Introduce
Asynchronous Caching in LRUQueryCache
URL: https://github.com/apache/lucene-solr/pull/815#discussion_r324321360
##########
File path: lucene/core/src/java/org/apache/lucene/search/LRUQueryCache.java
##########
@@ -726,14 +794,35 @@ public ScorerSupplier scorerSupplier(LeafReaderContext
context) throws IOExcepti
DocIdSet docIdSet;
try {
docIdSet = get(in.getQuery(), cacheHelper);
+ } catch (AsyncQueryLoadInProgressException e) {
+ // Query is being loaded asynchronously. Use uncached version but
+ // do not do a new load of the same query into the cache
+ return in.scorerSupplier(context);
} finally {
lock.unlock();
}
if (docIdSet == null) {
if (policy.shouldCache(in.getQuery())) {
- docIdSet = cache(context);
- putIfAbsent(in.getQuery(), docIdSet, cacheHelper);
+ // If asynchronous caching is requested, perform the same and return
+ // the uncached iterator
+ if (executor != null) {
+ FutureTask<Void> task = new FutureTask<>(() -> {
+ DocIdSet localDocIdSet = cache(context);
+ putIfAbsent(in.getQuery(), localDocIdSet, cacheHelper);
+
+ //remove the key from inflight -- the key is loaded now
+ inFlightAsyncLoadQueries.remove(in.getQuery());
+ return null;
+ });
+ inFlightAsyncLoadQueries.add(in.getQuery());
Review comment:
I think we have a concurrency bug here -- if the same query across different
threads is checked for caching, then two threads can get to this point, and
both can compute the cached result and store it? Because, this `.add` happens
at a different time from the above check (`.contains`)...
Maybe this doesn't matter? It just means two threads do the work of
caching, and one is wasted?
----------------------------------------------------------------
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.
For queries about this service, please contact Infrastructure at:
us...@infra.apache.org
With regards,
Apache Git Services
---------------------------------------------------------------------
To unsubscribe, e-mail: issues-unsubscr...@lucene.apache.org
For additional commands, e-mail: issues-h...@lucene.apache.org
