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https://issues.apache.org/jira/browse/BEAM-9824?focusedWorklogId=427584&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-427584
]
ASF GitHub Bot logged work on BEAM-9824:
----------------------------------------
Author: ASF GitHub Bot
Created on: 27/Apr/20 10:35
Start Date: 27/Apr/20 10:35
Worklog Time Spent: 10m
Work Description: mxm commented on a change in pull request #11530:
URL: https://github.com/apache/beam/pull/11530#discussion_r415698500
##########
File path:
runners/flink/src/test/java/org/apache/beam/runners/flink/batch/ReshuffleTest.java
##########
@@ -0,0 +1,94 @@
+/*
+ * 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.beam.runners.flink.batch;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.UUID;
+import org.apache.beam.runners.flink.FlinkPipelineOptions;
+import org.apache.beam.runners.flink.FlinkTestPipeline;
+import org.apache.beam.sdk.Pipeline;
+import org.apache.beam.sdk.testing.PAssert;
+import org.apache.beam.sdk.transforms.Create;
+import org.apache.beam.sdk.transforms.DoFn;
+import org.apache.beam.sdk.transforms.ParDo;
+import org.apache.beam.sdk.transforms.Reshuffle;
+import org.apache.beam.sdk.values.PCollection;
+import org.junit.Assert;
+import org.junit.Test;
+
+public class ReshuffleTest {
+
+ private static class WithBundleIdFn extends DoFn<String, String> {
+
+ private String uuid;
+
+ @StartBundle
+ public void startBundle() {
+ uuid = UUID.randomUUID().toString();
+ }
+
+ @ProcessElement
+ public void processElement(ProcessContext ctx) {
+ ctx.output(ctx.element() + "@" + uuid);
+ }
+ }
+
+ @Test
+ public void testMultipleReshufflesOnBatch() {
Review comment:
Or change the name, e.g.
`testEqualDistributionOnReshuffleAcrossMultipleStages` or something catchier ;)
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Issue Time Tracking
-------------------
Worklog Id: (was: 427584)
Time Spent: 0.5h (was: 20m)
> Multiple reshuffles are ignored in some cases on Flink batch runner.
> --------------------------------------------------------------------
>
> Key: BEAM-9824
> URL: https://issues.apache.org/jira/browse/BEAM-9824
> Project: Beam
> Issue Type: Bug
> Components: runner-flink
> Affects Versions: 2.19.0, 2.20.0
> Reporter: David Morávek
> Assignee: David Morávek
> Priority: Major
> Fix For: 2.22.0
>
> Time Spent: 0.5h
> Remaining Estimate: 0h
>
> Multiple reshuffles are ignored in some cases on Flink batch runner. This may
> lead to huge performace penalty in IO connectors (when reshuffling splits).
> In flink optimizer, when we `.rebalance()` dataset, is output channel is
> marked as `FORCED_REBALANCED`. When we chain this with another
> `.rebalance()`, the latter is ignored because it's source is already
> `FORCED_REBALANCED`, thus requested property is met. This is correct beaviour
> because rebalance is idempotent.
> When we include `flatMap` in between rebalances ->
> `.rebalance().flatMap(...).rebalance()`, we need to reshuffle again, because
> dataset distribution may have changed (eg. you can possibli emit unbouded
> stream from a single element). Unfortunatelly `flatMap` output is still
> incorrectly marked as `FORCED_REBALANCED` and the second reshuffle gets
> ignored.
> This especially affects IO connectors -> `FileIO.match()` returns reshuffled
> list of matched files -> we split each file into ranges -> **reshuffle** ->
> read. Ignoring the second reshuffle leads to huge perf. degradation (5m -> 2h
> in one of our production pipelines)
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