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https://issues.apache.org/jira/browse/FLINK-20772?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17799718#comment-17799718
]
Zakelly Lan commented on FLINK-20772:
-------------------------------------
[~dorbae] Glad you are back! And sorry for my hurry. Hope you have the
opportunity to contribute next time. :)
> RocksDBValueState with TTL occurs NullPointerException when calling
> update(null) method
> ----------------------------------------------------------------------------------------
>
> Key: FLINK-20772
> URL: https://issues.apache.org/jira/browse/FLINK-20772
> Project: Flink
> Issue Type: Bug
> Components: Runtime / State Backends
> Affects Versions: 1.11.2
> Environment: Flink version: 1.11.2
> Flink Cluster: Standalone cluster with 3 Job managers and Task managers on
> CentOS 7
> Reporter: Seongbae Chang
> Assignee: Zakelly Lan
> Priority: Not a Priority
> Labels: auto-deprioritized-major, auto-deprioritized-minor,
> beginner, pull-request-available
> Fix For: 1.19.0
>
>
> h2. Problem
> * I use ValueState for my custom trigger and set TTL for these ValueState in
> RocksDB backend environment.
> * I found an error when I used this code. I know that
> ValueState.update(null) works equally to ValueState.clear() in general.
> Unfortunately, this error occurs after using TTL
> {code:java}
> // My Code
> ctx.getPartitionedState(batchTotalSizeStateDesc).update(null);
> {code}
> * I tested this in Flink 1.11.2, but I think it would be a problem in upper
> versions.
> * Plus, I'm a beginner. So, if there is any problem in this discussion
> issue, please give me advice about that. And I'll fix it!
> {code:java}
> // Error Stacktrace
> Caused by: TimerException{org.apache.flink.util.FlinkRuntimeException: Error
> while adding data to RocksDB}
> ... 12 more
> Caused by: org.apache.flink.util.FlinkRuntimeException: Error while adding
> data to RocksDB
> at
> org.apache.flink.contrib.streaming.state.RocksDBValueState.update(RocksDBValueState.java:108)
> at
> org.apache.flink.runtime.state.ttl.TtlValueState.update(TtlValueState.java:50)
> at <MY-CLASS>.onProcessingTime(ActionBatchTimeTrigger.java:102)
> at <MY-CLASS>.onProcessingTime(ActionBatchTimeTrigger.java:29)
> at
> org.apache.flink.streaming.runtime.operators.windowing.WindowOperator$Context.onProcessingTime(WindowOperator.java:902)
> at
> org.apache.flink.streaming.runtime.operators.windowing.WindowOperator.onProcessingTime(WindowOperator.java:498)
> at
> org.apache.flink.streaming.api.operators.InternalTimerServiceImpl.onProcessingTime(InternalTimerServiceImpl.java:260)
> at
> org.apache.flink.streaming.runtime.tasks.StreamTask.invokeProcessingTimeCallback(StreamTask.java:1220)
> ... 11 more
> Caused by: java.lang.NullPointerException
> at
> org.apache.flink.api.common.typeutils.base.IntSerializer.serialize(IntSerializer.java:69)
> at
> org.apache.flink.api.common.typeutils.base.IntSerializer.serialize(IntSerializer.java:32)
> at
> org.apache.flink.api.common.typeutils.CompositeSerializer.serialize(CompositeSerializer.java:142)
> at
> org.apache.flink.contrib.streaming.state.AbstractRocksDBState.serializeValueInternal(AbstractRocksDBState.java:158)
> at
> org.apache.flink.contrib.streaming.state.AbstractRocksDBState.serializeValue(AbstractRocksDBState.java:178)
> at
> org.apache.flink.contrib.streaming.state.AbstractRocksDBState.serializeValue(AbstractRocksDBState.java:167)
> at
> org.apache.flink.contrib.streaming.state.RocksDBValueState.update(RocksDBValueState.java:106)
> ... 18 more
> {code}
>
> h2. Reason
> * It relates to RocksDBValueState with TTLValueState
> * In RocksDBValueState(as well as other types of ValueState),
> *.update(null)* has to be caught in if-clauses(null checking). However, it
> skips the null checking and then tries to serialize the null value.
> {code:java}
> //
> https://github.com/apache/flink/blob/release-1.11/flink-state-backends/flink-statebackend-rocksdb/src/main/java/org/apache/flink/contrib/streaming/state/RocksDBValueState.java#L96-L110
> @Override
> public void update(V value) {
> if (value == null) {
> clear();
> return;
> }
>
> try {
> backend.db.put(columnFamily, writeOptions,
> serializeCurrentKeyWithGroupAndNamespace(), serializeValue(value));
> } catch (Exception e) {
> throw new FlinkRuntimeException("Error while adding data to RocksDB",
> e);
> }
> }{code}
> * It is because that TtlValueState wraps the value(null) with the
> LastAccessTime and makes the new TtlValue Object with the null value.
> {code:java}
> //
> https://github.com/apache/flink/blob/release-1.11/flink-runtime/src/main/java/org/apache/flink/runtime/state/ttl/TtlValueState.java#L47-L51
> @Override
> public void update(T value) throws IOException {
> accessCallback.run();
> original.update(wrapWithTs(value));
> }
> {code}
> {code:java}
> //
> https://github.com/apache/flink/blob/release-1.11/flink-runtime/src/main/java/org/apache/flink/runtime/state/ttl/TtlUtils.java#L46-L48
> static <V> TtlValue<V> wrapWithTs(V value, long ts) {
> return new TtlValue<>(value, ts);
> }{code}
> {code:java}
> //
> https://github.com/apache/flink/blob/release-1.11/flink-runtime/src/main/java/org/apache/flink/runtime/state/ttl/TtlValue.java
> public class TtlValue<T> implements Serializable {
> private static final long serialVersionUID = 5221129704201125020L;
> @Nullable
> private final T userValue;
> private final long lastAccessTimestamp;
> public TtlValue(@Nullable T userValue, long lastAccessTimestamp) {
> this.userValue = userValue;
> this.lastAccessTimestamp = lastAccessTimestamp;
> }
> @Nullable
> public T getUserValue() {
> return userValue;
> }
> public long getLastAccessTimestamp() {
> return lastAccessTimestamp;
> }
> }
> {code}
> * In conclusion, I think that null checking logic has to be changed for
> checking whether userValue variable in TtlValue is null or not
>
> I hope that it would be helpful to improve Flink and if I have a chance, I
> want to fix it!
> Thank you and have a happy Christmas all!
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