gianm commented on a change in pull request #8116: remove unnecessary lock in
ForegroundCachePopulator leading to a lot of contention
URL: https://github.com/apache/incubator-druid/pull/8116#discussion_r305607617
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File path:
server/src/main/java/org/apache/druid/client/cache/BackgroundCachePopulator.java
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@@ -38,6 +38,13 @@
import java.util.concurrent.ExecutorService;
import java.util.function.Function;
+/**
+ * {@link CachePopulator} implementation that uses a {@link ExecutorService}
thread pool to populate a cache in the
+ * background. Used if config "druid.*.cache.numBackgroundThreads" is greater
than 0. If maximum cache entry size,
+ * specified by config "druid.*.cache.maxEntrySize", is exceeded, this {@link
CachePopulator} implementation will
+ * be a bit less efficient than {@link ForegroundCachePopulator} which can
stop retaining values early, in exchange
+ * for interacting with the {@link Cache} in a background thread.
Review comment:
I'd include a warning, too, about the lack of load shedding.
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