Details
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Improvement
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Status: Resolved
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Major
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Resolution: Fixed
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1.13.0, 1.14.0, 1.15.0
Description
- When loading a state, MultiStateKeyIterator load and bufferes the whole state in memory before it event processes a single data point
- This is absolutely no problem for small state (hence the unit tests work fine)
- MultiStateKeyIterator ctor sets up a java Stream that iterates all state descriptors and flattens all datapoints contained within
- The java.util.stream.Stream#flatMap function causes the buffering of the whole data set when enumerated later on
- See call stack [1]
- I our case this is 150e6 data points (> 1GiB just for the pointers to the data, let alone the data itself ~30GiB)
- I’m not aware of some instrumentation of Stream in order to avoid the problem, hence
- I coded an alternative implementation of MultiStateKeyIterator that avoids using java Stream,
- I can contribute our implementation (MultiStateKeyIteratorNoStreams)
[1]
Streams call stack:
hasNext:77, RocksStateKeysIterator (org.apache.flink.contrib.streaming.state.iterator)
next:82, RocksStateKeysIterator (org.apache.flink.contrib.streaming.state.iterator)
forEachRemaining:116, Iterator (java.util)
forEachRemaining:1801, Spliterators$IteratorSpliterator (java.util)
forEach:580, ReferencePipeline$Head (java.util.stream)
accept:270, ReferencePipeline$7$1 (java.util.stream) # <R> Stream<R> flatMap(final Function<? super P_OUT, ? extends Stream<? extends R>> var1)
accept:373, ReferencePipeline$11$1 (java.util.stream) # Stream<P_OUT> peek(final Consumer<? super P_OUT> var1)
accept:193, ReferencePipeline$3$1 (java.util.stream) # <R> Stream<R> map(final Function<? super P_OUT, ? extends R> var1)
tryAdvance:1359, ArrayList$ArrayListSpliterator (java.util)
lambda$initPartialTraversalState$0:294, StreamSpliterators$WrappingSpliterator (java.util.stream)
getAsBoolean:-1, 1528195520 (java.util.stream.StreamSpliterators$WrappingSpliterator$$Lambda$57)
fillBuffer:206, StreamSpliterators$AbstractWrappingSpliterator (java.util.stream)
doAdvance:161, StreamSpliterators$AbstractWrappingSpliterator (java.util.stream)
tryAdvance:300, StreamSpliterators$WrappingSpliterator (java.util.stream)
hasNext:681, Spliterators$1Adapter (java.util)
hasNext:83, MultiStateKeyIterator (org.apache.flink.state.api.input)
hasNext:162, KeyedStateReaderOperator$NamespaceDecorator (org.apache.flink.state.api.input.operator)
reachedEnd:215, KeyedStateInputFormat (org.apache.flink.state.api.input)
invoke:191, DataSourceTask (org.apache.flink.runtime.operators)
doRun:776, Task (org.apache.flink.runtime.taskmanager)
run:563, Task (org.apache.flink.runtime.taskmanager)
run:748, Thread (java.lang)
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