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Posted to commits@druid.apache.org by GitBox <gi...@apache.org> on 2020/03/02 19:15:26 UTC
[GitHub] [druid] ccaominh opened a new pull request #9448: Fix superbatch
merge last partition boundaries
ccaominh opened a new pull request #9448: Fix superbatch merge last partition boundaries
URL: https://github.com/apache/druid/pull/9448
### Description
A bug in the computation for the last parallel merge partition could cause an `IndexOutOfBoundsException` or precondition failure due to an empty partition.
<hr>
This PR has:
- [x] been self-reviewed.
- [x] added Javadocs for most classes and all non-trivial methods. Linked related entities via Javadoc links.
- [x] added comments explaining the "why" and the intent of the code wherever would not be obvious for an unfamiliar reader.
- [x] added unit tests or modified existing tests to cover new code paths.
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[GitHub] [druid] ccaominh merged pull request #9448: Fix superbatch merge
last partition boundaries
Posted by GitBox <gi...@apache.org>.
ccaominh merged pull request #9448: Fix superbatch merge last partition boundaries
URL: https://github.com/apache/druid/pull/9448
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[GitHub] [druid] jihoonson commented on a change in pull request #9448: Fix
superbatch merge last partition boundaries
Posted by GitBox <gi...@apache.org>.
jihoonson commented on a change in pull request #9448: Fix superbatch merge last partition boundaries
URL: https://github.com/apache/druid/pull/9448#discussion_r387316905
##########
File path: indexing-service/src/main/java/org/apache/druid/indexing/common/task/batch/parallel/ParallelIndexSupervisorTask.java
##########
@@ -760,29 +761,39 @@ private PartitionBoundaries determineRangePartition(Collection<StringDistributio
// See PartitionStat in GeneratedPartitionsReport.
final List<Pair<Interval, Integer>> partitions = new ArrayList<>(partitionToLocations.keySet());
Collections.shuffle(partitions, ThreadLocalRandom.current());
- final int numPartitionsPerTask = (int) Math.round(partitions.size() / (double) numMergeTasks);
final List<M> assignedPartitionLocations = new ArrayList<>(numMergeTasks);
- for (int i = 0; i < numMergeTasks - 1; i++) {
+ for (int i = 0; i < numMergeTasks; i++) {
+ Pair<Integer, Integer> partitionBoundaries = getPartitionBoundaries(i, partitions.size(), numMergeTasks);
final List<L> assignedToSameTask = partitions
- .subList(i * numPartitionsPerTask, (i + 1) * numPartitionsPerTask)
+ .subList(partitionBoundaries.lhs, partitionBoundaries.rhs)
.stream()
.flatMap(intervalAndPartitionId -> partitionToLocations.get(intervalAndPartitionId).stream())
.collect(Collectors.toList());
assignedPartitionLocations.add(createPartialSegmentMergeIOConfig.apply(assignedToSameTask));
}
- // The last task is assigned all remaining partitions.
- final List<L> assignedToSameTask = partitions
- .subList((numMergeTasks - 1) * numPartitionsPerTask, partitions.size())
- .stream()
- .flatMap(intervalAndPartitionId -> partitionToLocations.get(intervalAndPartitionId).stream())
- .collect(Collectors.toList());
- assignedPartitionLocations.add(createPartialSegmentMergeIOConfig.apply(assignedToSameTask));
-
return assignedPartitionLocations;
}
+ /**
+ * Partition items into as evenly-sized splits as possible.
+ *
+ * @param index index of partition
+ * @param total number of items to partitions
+ * @param splits number of desired partitions
+ *
+ * @return partition range: [lhs, rhs)
+ */
+ private static Pair<Integer, Integer> getPartitionBoundaries(int index, int total, int splits)
+ {
+ int chunk = total / splits;
+ int remainder = total % splits;
+ int start = index * chunk + (index < remainder ? index : remainder);
Review comment:
I think `index * (chunk + index < remainder ? 1 : 0)` is more clear.
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[GitHub] [druid] jihoonson commented on a change in pull request #9448: Fix
superbatch merge last partition boundaries
Posted by GitBox <gi...@apache.org>.
jihoonson commented on a change in pull request #9448: Fix superbatch merge last partition boundaries
URL: https://github.com/apache/druid/pull/9448#discussion_r387318051
##########
File path: indexing-service/src/main/java/org/apache/druid/indexing/common/task/batch/parallel/ParallelIndexSupervisorTask.java
##########
@@ -760,29 +761,39 @@ private PartitionBoundaries determineRangePartition(Collection<StringDistributio
// See PartitionStat in GeneratedPartitionsReport.
final List<Pair<Interval, Integer>> partitions = new ArrayList<>(partitionToLocations.keySet());
Collections.shuffle(partitions, ThreadLocalRandom.current());
- final int numPartitionsPerTask = (int) Math.round(partitions.size() / (double) numMergeTasks);
final List<M> assignedPartitionLocations = new ArrayList<>(numMergeTasks);
- for (int i = 0; i < numMergeTasks - 1; i++) {
+ for (int i = 0; i < numMergeTasks; i++) {
+ Pair<Integer, Integer> partitionBoundaries = getPartitionBoundaries(i, partitions.size(), numMergeTasks);
final List<L> assignedToSameTask = partitions
- .subList(i * numPartitionsPerTask, (i + 1) * numPartitionsPerTask)
+ .subList(partitionBoundaries.lhs, partitionBoundaries.rhs)
.stream()
.flatMap(intervalAndPartitionId -> partitionToLocations.get(intervalAndPartitionId).stream())
.collect(Collectors.toList());
assignedPartitionLocations.add(createPartialSegmentMergeIOConfig.apply(assignedToSameTask));
}
- // The last task is assigned all remaining partitions.
- final List<L> assignedToSameTask = partitions
- .subList((numMergeTasks - 1) * numPartitionsPerTask, partitions.size())
- .stream()
- .flatMap(intervalAndPartitionId -> partitionToLocations.get(intervalAndPartitionId).stream())
- .collect(Collectors.toList());
- assignedPartitionLocations.add(createPartialSegmentMergeIOConfig.apply(assignedToSameTask));
-
return assignedPartitionLocations;
}
+ /**
+ * Partition items into as evenly-sized splits as possible.
+ *
+ * @param index index of partition
+ * @param total number of items to partitions
+ * @param splits number of desired partitions
+ *
+ * @return partition range: [lhs, rhs)
+ */
+ private static Pair<Integer, Integer> getPartitionBoundaries(int index, int total, int splits)
+ {
+ int chunk = total / splits;
+ int remainder = total % splits;
+ int start = index * chunk + (index < remainder ? index : remainder);
Review comment:
I think the comment would be nice.
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[GitHub] [druid] maytasm3 commented on a change in pull request #9448: Fix
superbatch merge last partition boundaries
Posted by GitBox <gi...@apache.org>.
maytasm3 commented on a change in pull request #9448: Fix superbatch merge last partition boundaries
URL: https://github.com/apache/druid/pull/9448#discussion_r386626730
##########
File path: indexing-service/src/main/java/org/apache/druid/indexing/common/task/batch/parallel/ParallelIndexSupervisorTask.java
##########
@@ -760,29 +761,39 @@ private PartitionBoundaries determineRangePartition(Collection<StringDistributio
// See PartitionStat in GeneratedPartitionsReport.
final List<Pair<Interval, Integer>> partitions = new ArrayList<>(partitionToLocations.keySet());
Collections.shuffle(partitions, ThreadLocalRandom.current());
- final int numPartitionsPerTask = (int) Math.round(partitions.size() / (double) numMergeTasks);
final List<M> assignedPartitionLocations = new ArrayList<>(numMergeTasks);
- for (int i = 0; i < numMergeTasks - 1; i++) {
+ for (int i = 0; i < numMergeTasks; i++) {
+ Pair<Integer, Integer> partitionBoundaries = getPartitionBoundaries(i, partitions.size(), numMergeTasks);
final List<L> assignedToSameTask = partitions
- .subList(i * numPartitionsPerTask, (i + 1) * numPartitionsPerTask)
+ .subList(partitionBoundaries.lhs, partitionBoundaries.rhs)
.stream()
.flatMap(intervalAndPartitionId -> partitionToLocations.get(intervalAndPartitionId).stream())
.collect(Collectors.toList());
assignedPartitionLocations.add(createPartialSegmentMergeIOConfig.apply(assignedToSameTask));
}
- // The last task is assigned all remaining partitions.
- final List<L> assignedToSameTask = partitions
- .subList((numMergeTasks - 1) * numPartitionsPerTask, partitions.size())
- .stream()
- .flatMap(intervalAndPartitionId -> partitionToLocations.get(intervalAndPartitionId).stream())
- .collect(Collectors.toList());
- assignedPartitionLocations.add(createPartialSegmentMergeIOConfig.apply(assignedToSameTask));
-
return assignedPartitionLocations;
}
+ /**
+ * Partition items into as evenly-sized splits as possible.
+ *
+ * @param index index of partition
+ * @param total number of items to partitions
+ * @param splits number of desired partitions
+ *
+ * @return partition range: [lhs, rhs)
+ */
+ private static Pair<Integer, Integer> getPartitionBoundaries(int index, int total, int splits)
+ {
+ int chunk = total / splits;
+ int remainder = total % splits;
+ int start = index * chunk + (index < remainder ? index : remainder);
Review comment:
Can you add comment on purpose of `(index < remainder ? index : remainder)` ?
i.e. splitting the `remainder` across the first `remainder` tasks etc.
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[GitHub] [druid] maytasm3 commented on a change in pull request #9448: Fix
superbatch merge last partition boundaries
Posted by GitBox <gi...@apache.org>.
maytasm3 commented on a change in pull request #9448: Fix superbatch merge last partition boundaries
URL: https://github.com/apache/druid/pull/9448#discussion_r386628214
##########
File path: indexing-service/src/test/java/org/apache/druid/indexing/common/task/batch/parallel/ParallelIndexSupervisorTaskTest.java
##########
@@ -0,0 +1,121 @@
+/*
+ * 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.indexing.common.task.batch.parallel;
+
+import org.apache.druid.java.util.common.Intervals;
+import org.apache.druid.java.util.common.Pair;
+import org.joda.time.Interval;
+import org.junit.Assert;
+import org.junit.Test;
+import org.junit.experimental.runners.Enclosed;
+import org.junit.runner.RunWith;
+import org.junit.runners.Parameterized;
+
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
+import java.util.Map;
+import java.util.function.Function;
+import java.util.stream.Collectors;
+import java.util.stream.IntStream;
+
+@RunWith(Enclosed.class)
+public class ParallelIndexSupervisorTaskTest
+{
+ @RunWith(Parameterized.class)
+ public static class CreateMergeIoConfigsTest
+ {
+ private static final Function<List<HashPartitionLocation>, PartialHashSegmentMergeIOConfig>
+ CREATE_PARTIAL_SEGMENT_MERGE_IO_CONFIG = PartialHashSegmentMergeIOConfig::new;
+
+ @Parameterized.Parameters(name = "count = {0}")
+ public static Iterable<? extends Object> data()
+ {
+ // different scenarios for last (index = 10 - 1 = 9) partition:
+ return Arrays.asList(
+ 20, // even partitions per task: round(20 / 10) * (10 - 1) = 2 * 9 = 18 < 20
+ 24, // round down: round(24 / 10) * (10 - 1) = 2 * 9 = 18 < 24
+ 25, // round up to greater: round(25 / 10) * (10 - 1) = 3 * 9 = 27 > 25 (index out of bounds)
+ 27 // round up to equal: round(27 / 10) * (10 - 1) = 3 * 9 = 27 == 27 (empty partition)
+ );
+ }
+
+ @Parameterized.Parameter
+ public int count;
+
+ @Test
+ public void handlesLastPartitionCorrectly()
Review comment:
Some ideas for other assertions.
1) Verify that the split is evenly distributed. i.e. we should have 10 tasks with 2 each (for 20), 4 tasks with 3 and 6 tasks with 2 (for 24), etc.
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[GitHub] [druid] maytasm3 commented on a change in pull request #9448: Fix
superbatch merge last partition boundaries
Posted by GitBox <gi...@apache.org>.
maytasm3 commented on a change in pull request #9448: Fix superbatch merge last partition boundaries
URL: https://github.com/apache/druid/pull/9448#discussion_r386626841
##########
File path: indexing-service/src/main/java/org/apache/druid/indexing/common/task/batch/parallel/ParallelIndexSupervisorTask.java
##########
@@ -760,29 +761,39 @@ private PartitionBoundaries determineRangePartition(Collection<StringDistributio
// See PartitionStat in GeneratedPartitionsReport.
final List<Pair<Interval, Integer>> partitions = new ArrayList<>(partitionToLocations.keySet());
Collections.shuffle(partitions, ThreadLocalRandom.current());
- final int numPartitionsPerTask = (int) Math.round(partitions.size() / (double) numMergeTasks);
final List<M> assignedPartitionLocations = new ArrayList<>(numMergeTasks);
- for (int i = 0; i < numMergeTasks - 1; i++) {
+ for (int i = 0; i < numMergeTasks; i++) {
+ Pair<Integer, Integer> partitionBoundaries = getPartitionBoundaries(i, partitions.size(), numMergeTasks);
final List<L> assignedToSameTask = partitions
- .subList(i * numPartitionsPerTask, (i + 1) * numPartitionsPerTask)
+ .subList(partitionBoundaries.lhs, partitionBoundaries.rhs)
.stream()
.flatMap(intervalAndPartitionId -> partitionToLocations.get(intervalAndPartitionId).stream())
.collect(Collectors.toList());
assignedPartitionLocations.add(createPartialSegmentMergeIOConfig.apply(assignedToSameTask));
}
- // The last task is assigned all remaining partitions.
- final List<L> assignedToSameTask = partitions
- .subList((numMergeTasks - 1) * numPartitionsPerTask, partitions.size())
- .stream()
- .flatMap(intervalAndPartitionId -> partitionToLocations.get(intervalAndPartitionId).stream())
- .collect(Collectors.toList());
- assignedPartitionLocations.add(createPartialSegmentMergeIOConfig.apply(assignedToSameTask));
-
return assignedPartitionLocations;
}
+ /**
+ * Partition items into as evenly-sized splits as possible.
+ *
+ * @param index index of partition
+ * @param total number of items to partitions
+ * @param splits number of desired partitions
+ *
+ * @return partition range: [lhs, rhs)
+ */
+ private static Pair<Integer, Integer> getPartitionBoundaries(int index, int total, int splits)
+ {
+ int chunk = total / splits;
+ int remainder = total % splits;
+ int start = index * chunk + (index < remainder ? index : remainder);
+ int stop = start + chunk + (index < remainder ? 1 : 0);
Review comment:
same here for `(index < remainder ? 1 : 0)`
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[GitHub] [druid] jihoonson commented on a change in pull request #9448: Fix
superbatch merge last partition boundaries
Posted by GitBox <gi...@apache.org>.
jihoonson commented on a change in pull request #9448: Fix superbatch merge last partition boundaries
URL: https://github.com/apache/druid/pull/9448#discussion_r387314304
##########
File path: indexing-service/src/main/java/org/apache/druid/indexing/common/task/batch/parallel/ParallelIndexSupervisorTask.java
##########
@@ -760,29 +761,39 @@ private PartitionBoundaries determineRangePartition(Collection<StringDistributio
// See PartitionStat in GeneratedPartitionsReport.
final List<Pair<Interval, Integer>> partitions = new ArrayList<>(partitionToLocations.keySet());
Collections.shuffle(partitions, ThreadLocalRandom.current());
- final int numPartitionsPerTask = (int) Math.round(partitions.size() / (double) numMergeTasks);
final List<M> assignedPartitionLocations = new ArrayList<>(numMergeTasks);
- for (int i = 0; i < numMergeTasks - 1; i++) {
+ for (int i = 0; i < numMergeTasks; i++) {
+ Pair<Integer, Integer> partitionBoundaries = getPartitionBoundaries(i, partitions.size(), numMergeTasks);
final List<L> assignedToSameTask = partitions
- .subList(i * numPartitionsPerTask, (i + 1) * numPartitionsPerTask)
+ .subList(partitionBoundaries.lhs, partitionBoundaries.rhs)
.stream()
.flatMap(intervalAndPartitionId -> partitionToLocations.get(intervalAndPartitionId).stream())
.collect(Collectors.toList());
assignedPartitionLocations.add(createPartialSegmentMergeIOConfig.apply(assignedToSameTask));
}
- // The last task is assigned all remaining partitions.
- final List<L> assignedToSameTask = partitions
- .subList((numMergeTasks - 1) * numPartitionsPerTask, partitions.size())
- .stream()
- .flatMap(intervalAndPartitionId -> partitionToLocations.get(intervalAndPartitionId).stream())
- .collect(Collectors.toList());
- assignedPartitionLocations.add(createPartialSegmentMergeIOConfig.apply(assignedToSameTask));
-
return assignedPartitionLocations;
}
+ /**
+ * Partition items into as evenly-sized splits as possible.
+ *
+ * @param index index of partition
+ * @param total number of items to partitions
Review comment:
`to partition`?
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