[SPARK-24002] [SQL] Task not serializable caused by org.apache.parquet.io.api.Binary$ByteBufferBackedBinary.getBytes #21086
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
|
LGTM |
|
Test build #89464 has finished for PR 21086 at commit
|
|
Thanks! Merged to master |
|
If the community hit this issue, we can then backport it to Spark 2.3. |
|
I'm hitting this issue after upgrading from 2.0.2 to 2.3.0. Please backport this PR to Spark 2.3.0 |
ghoto
reviewed
May 16, 2018
| // Whole stage codegen (PhysicalRDD) is able to deal with batches directly | ||
| val returningBatch = supportBatch(sparkSession, resultSchema) | ||
|
|
||
| (file: PartitionedFile) => { | ||
| assert(file.partitionValues.numFields == partitionSchema.size) | ||
|
|
||
| // Try to push down filters when filter push-down is enabled. |
There was a problem hiding this comment.
So this code is the same as before. How can this solve the bug described in the head of the Conversation?
@gatorsmile
There was a problem hiding this comment.
Now the code is inside the read function, which will be executed at executor side. Thus we don't need to serialize ParquetFilters.
|
since people hit this issue, let's backport. cc @gatorsmile |
|
@ghoto Sure. Will backport it tonight. |
gatorsmile
added a commit
to gatorsmile/spark
that referenced
this pull request
May 17, 2018
….io.api.Binary$ByteBufferBackedBinary.getBytes ``` Py4JJavaError: An error occurred while calling o153.sql. : org.apache.spark.SparkException: Job aborted. at org.apache.spark.sql.execution.datasources.FileFormatWriter$.write(FileFormatWriter.scala:223) at org.apache.spark.sql.execution.datasources.InsertIntoHadoopFsRelationCommand.run(InsertIntoHadoopFsRelationCommand.scala:189) at org.apache.spark.sql.execution.command.ExecutedCommandExec.sideEffectResult$lzycompute(commands.scala:70) at org.apache.spark.sql.execution.command.ExecutedCommandExec.sideEffectResult(commands.scala:68) at org.apache.spark.sql.execution.command.ExecutedCommandExec.executeCollect(commands.scala:79) at org.apache.spark.sql.Dataset$$anonfun$6.apply(Dataset.scala:190) at org.apache.spark.sql.Dataset$$anonfun$6.apply(Dataset.scala:190) at org.apache.spark.sql.Dataset$$anonfun$59.apply(Dataset.scala:3021) at org.apache.spark.sql.execution.SQLExecution$.withCustomExecutionEnv(SQLExecution.scala:89) at org.apache.spark.sql.execution.SQLExecution$.withNewExecutionId(SQLExecution.scala:127) at org.apache.spark.sql.Dataset.withAction(Dataset.scala:3020) at org.apache.spark.sql.Dataset.<init>(Dataset.scala:190) at org.apache.spark.sql.Dataset$.ofRows(Dataset.scala:74) at org.apache.spark.sql.SparkSession.sql(SparkSession.scala:646) at sun.reflect.GeneratedMethodAccessor153.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:498) at py4j.reflection.MethodInvoker.invoke(MethodInvoker.java:244) at py4j.reflection.ReflectionEngine.invoke(ReflectionEngine.java:380) at py4j.Gateway.invoke(Gateway.java:293) at py4j.commands.AbstractCommand.invokeMethod(AbstractCommand.java:132) at py4j.commands.CallCommand.execute(CallCommand.java:79) at py4j.GatewayConnection.run(GatewayConnection.java:226) at java.lang.Thread.run(Thread.java:748) Caused by: org.apache.spark.SparkException: Exception thrown in Future.get: at org.apache.spark.sql.execution.exchange.BroadcastExchangeExec.doExecuteBroadcast(BroadcastExchangeExec.scala:190) at org.apache.spark.sql.execution.InputAdapter.doExecuteBroadcast(WholeStageCodegenExec.scala:267) at org.apache.spark.sql.execution.joins.BroadcastNestedLoopJoinExec.doConsume(BroadcastNestedLoopJoinExec.scala:530) at org.apache.spark.sql.execution.CodegenSupport$class.consume(WholeStageCodegenExec.scala:155) at org.apache.spark.sql.execution.ProjectExec.consume(basicPhysicalOperators.scala:37) at org.apache.spark.sql.execution.ProjectExec.doConsume(basicPhysicalOperators.scala:69) at org.apache.spark.sql.execution.CodegenSupport$class.consume(WholeStageCodegenExec.scala:155) at org.apache.spark.sql.execution.FilterExec.consume(basicPhysicalOperators.scala:144) ... at org.apache.spark.sql.execution.datasources.FileFormatWriter$.write(FileFormatWriter.scala:190) ... 23 more Caused by: java.util.concurrent.ExecutionException: org.apache.spark.SparkException: Task not serializable at java.util.concurrent.FutureTask.report(FutureTask.java:122) at java.util.concurrent.FutureTask.get(FutureTask.java:206) at org.apache.spark.sql.execution.exchange.BroadcastExchangeExec.doExecuteBroadcast(BroadcastExchangeExec.scala:179) ... 276 more Caused by: org.apache.spark.SparkException: Task not serializable at org.apache.spark.util.ClosureCleaner$.ensureSerializable(ClosureCleaner.scala:340) at org.apache.spark.util.ClosureCleaner$.org$apache$spark$util$ClosureCleaner$$clean(ClosureCleaner.scala:330) at org.apache.spark.util.ClosureCleaner$.clean(ClosureCleaner.scala:156) at org.apache.spark.SparkContext.clean(SparkContext.scala:2380) at org.apache.spark.rdd.RDD$$anonfun$mapPartitionsWithIndex$1.apply(RDD.scala:850) at org.apache.spark.rdd.RDD$$anonfun$mapPartitionsWithIndex$1.apply(RDD.scala:849) at org.apache.spark.rdd.RDDOperationScope$.withScope(RDDOperationScope.scala:151) at org.apache.spark.rdd.RDDOperationScope$.withScope(RDDOperationScope.scala:112) at org.apache.spark.rdd.RDD.withScope(RDD.scala:371) at org.apache.spark.rdd.RDD.mapPartitionsWithIndex(RDD.scala:849) at org.apache.spark.sql.execution.WholeStageCodegenExec.doExecute(WholeStageCodegenExec.scala:417) at org.apache.spark.sql.execution.SparkPlan$$anonfun$execute$1.apply(SparkPlan.scala:123) at org.apache.spark.sql.execution.SparkPlan$$anonfun$execute$1.apply(SparkPlan.scala:118) at org.apache.spark.sql.execution.SparkPlan$$anonfun$executeQuery$3.apply(SparkPlan.scala:152) at org.apache.spark.rdd.RDDOperationScope$.withScope(RDDOperationScope.scala:151) at org.apache.spark.sql.execution.SparkPlan.executeQuery(SparkPlan.scala:149) at org.apache.spark.sql.execution.SparkPlan.execute(SparkPlan.scala:118) at org.apache.spark.sql.execution.exchange.ShuffleExchangeExec.prepareShuffleDependency(ShuffleExchangeExec.scala:89) at org.apache.spark.sql.execution.exchange.ShuffleExchangeExec$$anonfun$doExecute$1.apply(ShuffleExchangeExec.scala:125) at org.apache.spark.sql.execution.exchange.ShuffleExchangeExec$$anonfun$doExecute$1.apply(ShuffleExchangeExec.scala:116) at org.apache.spark.sql.catalyst.errors.package$.attachTree(package.scala:52) at org.apache.spark.sql.execution.exchange.ShuffleExchangeExec.doExecute(ShuffleExchangeExec.scala:116) at org.apache.spark.sql.execution.SparkPlan$$anonfun$execute$1.apply(SparkPlan.scala:123) at org.apache.spark.sql.execution.SparkPlan$$anonfun$execute$1.apply(SparkPlan.scala:118) at org.apache.spark.sql.execution.SparkPlan$$anonfun$executeQuery$3.apply(SparkPlan.scala:152) at org.apache.spark.rdd.RDDOperationScope$.withScope(RDDOperationScope.scala:151) at org.apache.spark.sql.execution.SparkPlan.executeQuery(SparkPlan.scala:149) at org.apache.spark.sql.execution.SparkPlan.execute(SparkPlan.scala:118) at org.apache.spark.sql.execution.InputAdapter.inputRDDs(WholeStageCodegenExec.scala:271) at org.apache.spark.sql.execution.aggregate.HashAggregateExec.inputRDDs(HashAggregateExec.scala:181) at org.apache.spark.sql.execution.WholeStageCodegenExec.doExecute(WholeStageCodegenExec.scala:414) at org.apache.spark.sql.execution.SparkPlan$$anonfun$execute$1.apply(SparkPlan.scala:123) at org.apache.spark.sql.execution.SparkPlan$$anonfun$execute$1.apply(SparkPlan.scala:118) at org.apache.spark.sql.execution.SparkPlan$$anonfun$executeQuery$3.apply(SparkPlan.scala:152) at org.apache.spark.rdd.RDDOperationScope$.withScope(RDDOperationScope.scala:151) at org.apache.spark.sql.execution.SparkPlan.executeQuery(SparkPlan.scala:149) at org.apache.spark.sql.execution.SparkPlan.execute(SparkPlan.scala:118) at org.apache.spark.sql.execution.collect.Collector$.collect(Collector.scala:61) at org.apache.spark.sql.execution.collect.Collector$.collect(Collector.scala:70) at org.apache.spark.sql.execution.SparkPlan.executeCollectResult(SparkPlan.scala:264) at org.apache.spark.sql.execution.exchange.BroadcastExchangeExec$$anon$1$$anonfun$call$1.apply(BroadcastExchangeExec.scala:93) at org.apache.spark.sql.execution.exchange.BroadcastExchangeExec$$anon$1$$anonfun$call$1.apply(BroadcastExchangeExec.scala:81) at org.apache.spark.sql.execution.SQLExecution$.withExecutionId(SQLExecution.scala:150) at org.apache.spark.sql.execution.exchange.BroadcastExchangeExec$$anon$1.call(BroadcastExchangeExec.scala:80) at org.apache.spark.sql.execution.exchange.BroadcastExchangeExec$$anon$1.call(BroadcastExchangeExec.scala:76) at java.util.concurrent.FutureTask.run(FutureTask.java:266) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) ... 1 more Caused by: java.nio.BufferUnderflowException at java.nio.HeapByteBuffer.get(HeapByteBuffer.java:151) at java.nio.ByteBuffer.get(ByteBuffer.java:715) at org.apache.parquet.io.api.Binary$ByteBufferBackedBinary.getBytes(Binary.java:405) at org.apache.parquet.io.api.Binary$ByteBufferBackedBinary.getBytesUnsafe(Binary.java:414) at org.apache.parquet.io.api.Binary$ByteBufferBackedBinary.writeObject(Binary.java:484) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:498) at java.io.ObjectStreamClass.invokeWriteObject(ObjectStreamClass.java:1128) at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1496) ``` The Parquet filters are serializable but not thread safe. SparkPlan.prepare() could be called in different threads (BroadcastExchange will call it in a thread pool). Thus, we could serialize the same Parquet filter at the same time. This is not easily reproduced. The fix is to avoid serializing these Parquet filters in the driver. This PR is to avoid serializing these Parquet filters by moving the parquet filter generation from the driver to executors. Having two queries one is a 1000-line SQL query and a 3000-line SQL query. Need to run at least one hour with a heavy write workload to reproduce once. Author: gatorsmile <gatorsmile@gmail.com> Closes apache#21086 from gatorsmile/taskNotSerializable.
asfgit
pushed a commit
that referenced
this pull request
May 17, 2018
…apache.parquet.io.api.Binary$ByteBufferBackedBinary.getBytes This PR is to backport #21086 to Apache Spark 2.3 ---- ``` Py4JJavaError: An error occurred while calling o153.sql. : org.apache.spark.SparkException: Job aborted. at org.apache.spark.sql.execution.datasources.FileFormatWriter$.write(FileFormatWriter.scala:223) at org.apache.spark.sql.execution.datasources.InsertIntoHadoopFsRelationCommand.run(InsertIntoHadoopFsRelationCommand.scala:189) at org.apache.spark.sql.execution.command.ExecutedCommandExec.sideEffectResult$lzycompute(commands.scala:70) at org.apache.spark.sql.execution.command.ExecutedCommandExec.sideEffectResult(commands.scala:68) at org.apache.spark.sql.execution.command.ExecutedCommandExec.executeCollect(commands.scala:79) at org.apache.spark.sql.Dataset$$anonfun$6.apply(Dataset.scala:190) at org.apache.spark.sql.Dataset$$anonfun$6.apply(Dataset.scala:190) at org.apache.spark.sql.Dataset$$anonfun$59.apply(Dataset.scala:3021) at org.apache.spark.sql.execution.SQLExecution$.withCustomExecutionEnv(SQLExecution.scala:89) at org.apache.spark.sql.execution.SQLExecution$.withNewExecutionId(SQLExecution.scala:127) at org.apache.spark.sql.Dataset.withAction(Dataset.scala:3020) at org.apache.spark.sql.Dataset.<init>(Dataset.scala:190) at org.apache.spark.sql.Dataset$.ofRows(Dataset.scala:74) at org.apache.spark.sql.SparkSession.sql(SparkSession.scala:646) at sun.reflect.GeneratedMethodAccessor153.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:498) at py4j.reflection.MethodInvoker.invoke(MethodInvoker.java:244) at py4j.reflection.ReflectionEngine.invoke(ReflectionEngine.java:380) at py4j.Gateway.invoke(Gateway.java:293) at py4j.commands.AbstractCommand.invokeMethod(AbstractCommand.java:132) at py4j.commands.CallCommand.execute(CallCommand.java:79) at py4j.GatewayConnection.run(GatewayConnection.java:226) at java.lang.Thread.run(Thread.java:748) Caused by: org.apache.spark.SparkException: Exception thrown in Future.get: at org.apache.spark.sql.execution.exchange.BroadcastExchangeExec.doExecuteBroadcast(BroadcastExchangeExec.scala:190) at org.apache.spark.sql.execution.InputAdapter.doExecuteBroadcast(WholeStageCodegenExec.scala:267) at org.apache.spark.sql.execution.joins.BroadcastNestedLoopJoinExec.doConsume(BroadcastNestedLoopJoinExec.scala:530) at org.apache.spark.sql.execution.CodegenSupport$class.consume(WholeStageCodegenExec.scala:155) at org.apache.spark.sql.execution.ProjectExec.consume(basicPhysicalOperators.scala:37) at org.apache.spark.sql.execution.ProjectExec.doConsume(basicPhysicalOperators.scala:69) at org.apache.spark.sql.execution.CodegenSupport$class.consume(WholeStageCodegenExec.scala:155) at org.apache.spark.sql.execution.FilterExec.consume(basicPhysicalOperators.scala:144) ... at org.apache.spark.sql.execution.datasources.FileFormatWriter$.write(FileFormatWriter.scala:190) ... 23 more Caused by: java.util.concurrent.ExecutionException: org.apache.spark.SparkException: Task not serializable at java.util.concurrent.FutureTask.report(FutureTask.java:122) at java.util.concurrent.FutureTask.get(FutureTask.java:206) at org.apache.spark.sql.execution.exchange.BroadcastExchangeExec.doExecuteBroadcast(BroadcastExchangeExec.scala:179) ... 276 more Caused by: org.apache.spark.SparkException: Task not serializable at org.apache.spark.util.ClosureCleaner$.ensureSerializable(ClosureCleaner.scala:340) at org.apache.spark.util.ClosureCleaner$.org$apache$spark$util$ClosureCleaner$$clean(ClosureCleaner.scala:330) at org.apache.spark.util.ClosureCleaner$.clean(ClosureCleaner.scala:156) at org.apache.spark.SparkContext.clean(SparkContext.scala:2380) at org.apache.spark.rdd.RDD$$anonfun$mapPartitionsWithIndex$1.apply(RDD.scala:850) at org.apache.spark.rdd.RDD$$anonfun$mapPartitionsWithIndex$1.apply(RDD.scala:849) at org.apache.spark.rdd.RDDOperationScope$.withScope(RDDOperationScope.scala:151) at org.apache.spark.rdd.RDDOperationScope$.withScope(RDDOperationScope.scala:112) at org.apache.spark.rdd.RDD.withScope(RDD.scala:371) at org.apache.spark.rdd.RDD.mapPartitionsWithIndex(RDD.scala:849) at org.apache.spark.sql.execution.WholeStageCodegenExec.doExecute(WholeStageCodegenExec.scala:417) at org.apache.spark.sql.execution.SparkPlan$$anonfun$execute$1.apply(SparkPlan.scala:123) at org.apache.spark.sql.execution.SparkPlan$$anonfun$execute$1.apply(SparkPlan.scala:118) at org.apache.spark.sql.execution.SparkPlan$$anonfun$executeQuery$3.apply(SparkPlan.scala:152) at org.apache.spark.rdd.RDDOperationScope$.withScope(RDDOperationScope.scala:151) at org.apache.spark.sql.execution.SparkPlan.executeQuery(SparkPlan.scala:149) at org.apache.spark.sql.execution.SparkPlan.execute(SparkPlan.scala:118) at org.apache.spark.sql.execution.exchange.ShuffleExchangeExec.prepareShuffleDependency(ShuffleExchangeExec.scala:89) at org.apache.spark.sql.execution.exchange.ShuffleExchangeExec$$anonfun$doExecute$1.apply(ShuffleExchangeExec.scala:125) at org.apache.spark.sql.execution.exchange.ShuffleExchangeExec$$anonfun$doExecute$1.apply(ShuffleExchangeExec.scala:116) at org.apache.spark.sql.catalyst.errors.package$.attachTree(package.scala:52) at org.apache.spark.sql.execution.exchange.ShuffleExchangeExec.doExecute(ShuffleExchangeExec.scala:116) at org.apache.spark.sql.execution.SparkPlan$$anonfun$execute$1.apply(SparkPlan.scala:123) at org.apache.spark.sql.execution.SparkPlan$$anonfun$execute$1.apply(SparkPlan.scala:118) at org.apache.spark.sql.execution.SparkPlan$$anonfun$executeQuery$3.apply(SparkPlan.scala:152) at org.apache.spark.rdd.RDDOperationScope$.withScope(RDDOperationScope.scala:151) at org.apache.spark.sql.execution.SparkPlan.executeQuery(SparkPlan.scala:149) at org.apache.spark.sql.execution.SparkPlan.execute(SparkPlan.scala:118) at org.apache.spark.sql.execution.InputAdapter.inputRDDs(WholeStageCodegenExec.scala:271) at org.apache.spark.sql.execution.aggregate.HashAggregateExec.inputRDDs(HashAggregateExec.scala:181) at org.apache.spark.sql.execution.WholeStageCodegenExec.doExecute(WholeStageCodegenExec.scala:414) at org.apache.spark.sql.execution.SparkPlan$$anonfun$execute$1.apply(SparkPlan.scala:123) at org.apache.spark.sql.execution.SparkPlan$$anonfun$execute$1.apply(SparkPlan.scala:118) at org.apache.spark.sql.execution.SparkPlan$$anonfun$executeQuery$3.apply(SparkPlan.scala:152) at org.apache.spark.rdd.RDDOperationScope$.withScope(RDDOperationScope.scala:151) at org.apache.spark.sql.execution.SparkPlan.executeQuery(SparkPlan.scala:149) at org.apache.spark.sql.execution.SparkPlan.execute(SparkPlan.scala:118) at org.apache.spark.sql.execution.collect.Collector$.collect(Collector.scala:61) at org.apache.spark.sql.execution.collect.Collector$.collect(Collector.scala:70) at org.apache.spark.sql.execution.SparkPlan.executeCollectResult(SparkPlan.scala:264) at org.apache.spark.sql.execution.exchange.BroadcastExchangeExec$$anon$1$$anonfun$call$1.apply(BroadcastExchangeExec.scala:93) at org.apache.spark.sql.execution.exchange.BroadcastExchangeExec$$anon$1$$anonfun$call$1.apply(BroadcastExchangeExec.scala:81) at org.apache.spark.sql.execution.SQLExecution$.withExecutionId(SQLExecution.scala:150) at org.apache.spark.sql.execution.exchange.BroadcastExchangeExec$$anon$1.call(BroadcastExchangeExec.scala:80) at org.apache.spark.sql.execution.exchange.BroadcastExchangeExec$$anon$1.call(BroadcastExchangeExec.scala:76) at java.util.concurrent.FutureTask.run(FutureTask.java:266) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) ... 1 more Caused by: java.nio.BufferUnderflowException at java.nio.HeapByteBuffer.get(HeapByteBuffer.java:151) at java.nio.ByteBuffer.get(ByteBuffer.java:715) at org.apache.parquet.io.api.Binary$ByteBufferBackedBinary.getBytes(Binary.java:405) at org.apache.parquet.io.api.Binary$ByteBufferBackedBinary.getBytesUnsafe(Binary.java:414) at org.apache.parquet.io.api.Binary$ByteBufferBackedBinary.writeObject(Binary.java:484) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:498) at java.io.ObjectStreamClass.invokeWriteObject(ObjectStreamClass.java:1128) at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1496) ``` The Parquet filters are serializable but not thread safe. SparkPlan.prepare() could be called in different threads (BroadcastExchange will call it in a thread pool). Thus, we could serialize the same Parquet filter at the same time. This is not easily reproduced. The fix is to avoid serializing these Parquet filters in the driver. This PR is to avoid serializing these Parquet filters by moving the parquet filter generation from the driver to executors. ## How was this patch tested? Having two queries one is a 1000-line SQL query and a 3000-line SQL query. Need to run at least one hour with a heavy write workload to reproduce once. Author: gatorsmile <gatorsmile@gmail.com> Closes #21351 from gatorsmile/backportSPARK-24002.
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
What changes were proposed in this pull request?
The Parquet filters are serializable but not thread safe. SparkPlan.prepare() could be called in different threads (BroadcastExchange will call it in a thread pool). Thus, we could serialize the same Parquet filter at the same time. This is not easily reproduced. The fix is to avoid serializing these Parquet filters in the driver. This PR is to avoid serializing these Parquet filters by moving the parquet filter generation from the driver to executors.
How was this patch tested?
Having two queries one is a 1000-line SQL query and a 3000-line SQL query. Need to run at least one hour with a heavy write workload to reproduce once.