Github user sohami commented on a diff in the pull request:
https://github.com/apache/drill/pull/639#discussion_r86605131
--- Diff:
exec/java-exec/src/main/java/org/apache/drill/exec/planner/fragment/LocalAffinityFragmentParallelizer.java
---
@@ -0,0 +1,165 @@
+/**
+ * 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
+ * <p/>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p/>
+ * 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.drill.exec.planner.fragment;
+
+import com.google.common.collect.Lists;
+import com.google.common.collect.Ordering;
+import org.apache.drill.exec.physical.EndpointAffinity;
+import org.apache.drill.exec.physical.PhysicalOperatorSetupException;
+import org.apache.drill.exec.proto.CoordinationProtos.DrillbitEndpoint;
+
+import java.util.Map;
+import java.util.List;
+import java.util.Collection;
+import java.util.HashMap;
+import java.util.Collections;
+
+/**
+ * Implementation of {@link FragmentParallelizer} where fragment has zero
or more endpoints.
+ * This is for Parquet Scan Fragments only. Fragment placement is done
preferring
+ * data locality.
+ */
+public class LocalAffinityFragmentParallelizer implements
FragmentParallelizer {
+ public static final LocalAffinityFragmentParallelizer INSTANCE = new
LocalAffinityFragmentParallelizer();
+
+ // Sort a list of map entries by values.
+ Ordering<Map.Entry<DrillbitEndpoint, Integer>> sortByValues = new
Ordering<Map.Entry<DrillbitEndpoint, Integer>>() {
+ @Override
+ public int compare(Map.Entry<DrillbitEndpoint, Integer> left,
Map.Entry<DrillbitEndpoint, Integer> right) {
+ return right.getValue().compareTo(left.getValue());
+ }
+ };
+
+ @Override
+ public void parallelizeFragment(final Wrapper fragmentWrapper, final
ParallelizationParameters parameters,
+ final Collection<DrillbitEndpoint>
activeEndpoints) throws PhysicalOperatorSetupException {
+ final Stats stats = fragmentWrapper.getStats();
+ final ParallelizationInfo parallelizationInfo =
stats.getParallelizationInfo();
+ final Map<DrillbitEndpoint, EndpointAffinity> endpointAffinityMap =
+
fragmentWrapper.getStats().getParallelizationInfo().getEndpointAffinityMap();
+ int totalWorkUnits = 0;
+ Map<DrillbitEndpoint, Integer> endpointPool = new HashMap<>();
+
+ // Get the total number of work units and list of endPoints to
schedule fragments on
+ for (Map.Entry<DrillbitEndpoint, EndpointAffinity> epAff :
endpointAffinityMap.entrySet()) {
+ if (epAff.getValue().getNumLocalWorkUnits() > 0) {
+ totalWorkUnits += epAff.getValue().getNumLocalWorkUnits();
+ endpointPool.put(epAff.getKey(),
epAff.getValue().getNumLocalWorkUnits());
+ }
+ }
+
+ // Find the parallelization width of fragment
+ // 1. Find the parallelization based on cost. Use max cost of all
operators in this fragment; this is consistent
+ // with the calculation that ExcessiveExchangeRemover uses.
+ int width = (int) Math.ceil(stats.getMaxCost() /
parameters.getSliceTarget());
+
+ // 2. Cap the parallelization width by fragment level width limit
and system level per query width limit
+ width = Math.min(width,
Math.min(parallelizationInfo.getMaxWidth(), parameters.getMaxGlobalWidth()));
+
+ // 3. Cap the parallelization width by system level per node width
limit
+ width = Math.min(width, parameters.getMaxWidthPerNode() *
endpointPool.size());
+
+ // 4. Make sure width is at least the min width enforced by
operators
+ width = Math.max(parallelizationInfo.getMinWidth(), width);
+
+ // 5. Make sure width is at most the max width enforced by
operators
+ width = Math.min(parallelizationInfo.getMaxWidth(), width);
+
+ // 6: Finally make sure the width is at least one
+ width = Math.max(1, width);
+
+ List<DrillbitEndpoint> assignedEndPoints = Lists.newArrayList();
+ int totalAssigned = 0;
+
+ // Sort the endpointPool based on numLocalWorkUnits. This sorting
is done because we are doing
+ // round robin allocation and we stop when we reach the width. We
want to allocate
+ // on endpoints which have higher numLocalWorkUnits first.
+ List<Map.Entry<DrillbitEndpoint, Integer>> sortedEndpointPool =
Lists.newArrayList(endpointPool.entrySet());
+ Collections.sort(sortedEndpointPool, sortByValues);
+
+ // Keep track of number of fragments allocated to each endpoint.
+ Map<DrillbitEndpoint, Integer> endpointAssignments = new
HashMap<>();
+
+ // Keep track of how many more to assign to each endpoint.
+ Map<DrillbitEndpoint, Integer> remainingEndpointAssignments = new
HashMap<>();
+
+ // Calculate the target allocation for each endPoint based on work
it has to do
+ // Assign one fragment (minimum) to all the endPoints in the pool.
+ for (DrillbitEndpoint ep : endpointPool.keySet()) {
+ final int targetAllocation = (int)
Math.ceil(endpointAffinityMap.get(ep).getNumLocalWorkUnits() * ((double)width /
parallelizationInfo.getMaxWidth()));
+ assignedEndPoints.add(ep);
+ totalAssigned++;
+ remainingEndpointAssignments.put(ep, targetAllocation-1);
+ endpointAssignments.put(ep, 1);
+ }
+
+ // Keep allocating from endpoints in a round robin fashion upto
+ // max(targetAllocation, maxwidthPerNode) for each endpoint and
--- End diff --
Wrong comment.. We assign until we reach limit of maxWidthPerNode
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