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https://issues.apache.org/jira/browse/FLINK-20663?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17317865#comment-17317865
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Huang Xingbo commented on FLINK-20663:
--------------------------------------
[~zhou_yb] If some udfs can be chained together, they will be executed in the
same Python Operator. In this situation, we don't need to split them. So what
needs to be split are multiple Python Operators in a slot, and then separate
them into different slot sharing group. the progress is : table ->
datastream.map.slot_sharing_group -> table
> Managed memory may not be released in time when operators use managed memory
> frequently
> ---------------------------------------------------------------------------------------
>
> Key: FLINK-20663
> URL: https://issues.apache.org/jira/browse/FLINK-20663
> Project: Flink
> Issue Type: Bug
> Components: Runtime / Task
> Affects Versions: 1.12.0
> Reporter: Caizhi Weng
> Assignee: Xintong Song
> Priority: Critical
> Labels: pull-request-available
> Fix For: 1.12.2, 1.13.0
>
> Attachments: exception, summary.py, taskmanager.log
>
>
> Some batch operators (like sort merge join or hash aggregate) use managed
> memory frequently. When these operators are chained together and the cluster
> load is a bit heavy, it is very likely that the following exception occurs:
> {code:java}
> 2020-12-18 10:04:32
> java.lang.RuntimeException:
> org.apache.flink.runtime.memory.MemoryAllocationException: Could not allocate
> 512 pages
> at
> org.apache.flink.table.runtime.util.LazyMemorySegmentPool.nextSegment(LazyMemorySegmentPool.java:85)
> at
> org.apache.flink.runtime.io.disk.SimpleCollectingOutputView.<init>(SimpleCollectingOutputView.java:49)
> at
> org.apache.flink.table.runtime.operators.aggregate.BytesHashMap$RecordArea.<init>(BytesHashMap.java:297)
> at
> org.apache.flink.table.runtime.operators.aggregate.BytesHashMap.<init>(BytesHashMap.java:103)
> at
> org.apache.flink.table.runtime.operators.aggregate.BytesHashMap.<init>(BytesHashMap.java:90)
> at LocalHashAggregateWithKeys$209161.open(Unknown Source)
> at
> org.apache.flink.streaming.runtime.tasks.OperatorChain.initializeStateAndOpenOperators(OperatorChain.java:401)
> at
> org.apache.flink.streaming.runtime.tasks.StreamTask.lambda$beforeInvoke$2(StreamTask.java:506)
> at
> org.apache.flink.streaming.runtime.tasks.StreamTaskActionExecutor$SynchronizedStreamTaskActionExecutor.runThrowing(StreamTaskActionExecutor.java:92)
> at
> org.apache.flink.streaming.runtime.tasks.StreamTask.beforeInvoke(StreamTask.java:501)
> at
> org.apache.flink.streaming.runtime.tasks.StreamTask.invoke(StreamTask.java:530)
> at org.apache.flink.runtime.taskmanager.Task.doRun(Task.java:722)
> at org.apache.flink.runtime.taskmanager.Task.run(Task.java:547)
> at java.lang.Thread.run(Thread.java:834)
> Suppressed: java.lang.NullPointerException
> at LocalHashAggregateWithKeys$209161.close(Unknown Source)
> at
> org.apache.flink.table.runtime.operators.TableStreamOperator.dispose(TableStreamOperator.java:46)
> at
> org.apache.flink.streaming.runtime.tasks.StreamTask.disposeAllOperators(StreamTask.java:739)
> at
> org.apache.flink.streaming.runtime.tasks.StreamTask.runAndSuppressThrowable(StreamTask.java:719)
> at
> org.apache.flink.streaming.runtime.tasks.StreamTask.cleanUpInvoke(StreamTask.java:642)
> at
> org.apache.flink.streaming.runtime.tasks.StreamTask.invoke(StreamTask.java:551)
> ... 3 more
> Suppressed: java.lang.NullPointerException
> at LocalHashAggregateWithKeys$209766.close(Unknown
> Source)
> ... 8 more
> Caused by: org.apache.flink.runtime.memory.MemoryAllocationException: Could
> not allocate 512 pages
> at
> org.apache.flink.runtime.memory.MemoryManager.allocatePages(MemoryManager.java:231)
> at
> org.apache.flink.table.runtime.util.LazyMemorySegmentPool.nextSegment(LazyMemorySegmentPool.java:83)
> ... 13 more
> Caused by: org.apache.flink.runtime.memory.MemoryReservationException: Could
> not allocate 16777216 bytes, only 9961487 bytes are remaining. This usually
> indicates that you are requesting more memory than you have reserved.
> However, when running an old JVM version it can also be caused by slow
> garbage collection. Try to upgrade to Java 8u72 or higher if running on an
> old Java version.
> at
> org.apache.flink.runtime.memory.UnsafeMemoryBudget.reserveMemory(UnsafeMemoryBudget.java:164)
> at
> org.apache.flink.runtime.memory.UnsafeMemoryBudget.reserveMemory(UnsafeMemoryBudget.java:80)
> at
> org.apache.flink.runtime.memory.MemoryManager.allocatePages(MemoryManager.java:229)
> ... 14 more
> {code}
> It seems that this is caused by relying on GC to release managed memory, as
> {{System.gc()}} may not trigger GC in time. See {{UnsafeMemoryBudget.java}}.
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