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_r305607757
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File path:
server/src/main/java/org/apache/druid/client/cache/ForegroundCachePopulator.java
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@@ -22,16 +22,22 @@
import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.google.common.base.Preconditions;
+import org.apache.commons.lang.mutable.MutableBoolean;
import org.apache.druid.java.util.common.guava.Sequence;
import org.apache.druid.java.util.common.guava.SequenceWrapper;
import org.apache.druid.java.util.common.guava.Sequences;
import org.apache.druid.java.util.common.logger.Logger;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
-import java.util.concurrent.atomic.AtomicBoolean;
import java.util.function.Function;
+/**
+ * {@link CachePopulator} implementation that populates a cache on the same
thread that is processing the
+ * {@link Sequence}. Used if config "druid.*.cache.numBackgroundThreads" is 0
(the default). This {@link CachePopulator}
+ * should be more efficient than {@link BackgroundCachePopulator} if maximum
cache entry size, specified by config
+ * "druid.*.cache.maxEntrySize", is exceeded.
Review comment:
I'd add that typically, the thread processing this sequence (and hence
populating the cache) is either:
- a processing thread (if historical/task)
- an http thread (if broker)
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