[GitHub] [incubator-druid] dclim commented on a change in pull request #8038: Making optimal usage of multiple segment cache locations

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dclim commented on a change in pull request #8038: Making optimal usage of multiple segment cache locations
URL: https://github.com/apache/incubator-druid/pull/8038#discussion_r325987391
 
 

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 File path: server/src/main/java/org/apache/druid/segment/loading/LeastBytesUsedStorageLocationSelectorStrategy.java
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 @@ -0,0 +1,51 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.apache.druid.segment.loading;
+
+import com.google.common.collect.ImmutableList;
+import com.google.common.collect.Ordering;
+import org.apache.druid.timeline.DataSegment;
+
+import java.util.Comparator;
+import java.util.Iterator;
+
+/**
+ * A {@link StorageLocation} selector strategy that selects a segment cache location that is least filled each time
+ * among the available storage locations.
+ */
+public class LeastBytesUsedStorageLocationSelectorStrategy implements StorageLocationSelectorStrategy
+{
+  private static final Comparator<StorageLocation> COMPARATOR = Comparator
+      .comparingLong(StorageLocation::currSizeBytes);
+
+  private ImmutableList<StorageLocation> storageLocations;
+
+  @Override
+  public Iterator<StorageLocation> getLocations(DataSegment dataSegment, String storageDirStr)
+  {
+    return Ordering.from(COMPARATOR).sortedCopy(this.storageLocations).iterator();
 
 Review comment:
   @jihoonson I agree - so long as the segment eventually gets loaded into a segment cache location (even if it's on the next coordinator run) and we don't get into an inconsistent state as a result of a concurrent threads both picking a location that only has room for one of the segments, I think this is acceptable. Thank you for your thorough review of this PR!

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