[
https://issues.apache.org/jira/browse/FLINK-9269?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16460806#comment-16460806
]
ASF GitHub Bot commented on FLINK-9269:
---------------------------------------
Github user StefanRRichter commented on the issue:
https://github.com/apache/flink/pull/5934
Yes, there is a theoretical problem if the serialization would not be
threadsafe. I think currently the silent assumption that holds is that
serializers are immutable w.r.t. serialization after they have been created and
passed to create a state. I think Stephan's suggestion would be the right
approach to materialize that assumption into code and also gain a bit of
efficiency.
I think the other concurrency problem is a problem that comes from lazy
state registration, and I assume most jobs use de-facto eager state
registration, so all the state is registered in `open()` or
`initializeState(...)`, and they are never changed at runtime. For the few
remaining jobs, there must also be a certain timing that they need to register
a new state while a checkpoint is running. Overall, I think those are the
reasons why there is no reported case of a problem from this in practice. But I
agree this should be addressed and is also very easy to fix.
> Concurrency problem in HeapKeyedStateBackend when performing checkpoint async
> -----------------------------------------------------------------------------
>
> Key: FLINK-9269
> URL: https://issues.apache.org/jira/browse/FLINK-9269
> Project: Flink
> Issue Type: Bug
> Components: State Backends, Checkpointing
> Affects Versions: 1.5.0
> Reporter: Sihua Zhou
> Assignee: Sihua Zhou
> Priority: Critical
> Fix For: 1.5.0
>
>
> {code:java}
> @Test
> public void testConccurrencyProblem() throws Exception {
> CheckpointStreamFactory streamFactory = createStreamFactory();
> Environment env = new DummyEnvironment();
> AbstractKeyedStateBackend<Integer> backend =
> createKeyedBackend(IntSerializer.INSTANCE, env);
> try {
> long checkpointID = 0;
> List<Future> futureList = new ArrayList();
> for (int i = 0; i < 10; ++i) {
> ValueStateDescriptor<Integer> kvId = new
> ValueStateDescriptor<>("id" + i, IntSerializer.INSTANCE);
> ValueState<Integer> state =
> backend.getOrCreateKeyedState(VoidNamespaceSerializer.INSTANCE, kvId);
> ((InternalValueState)
> state).setCurrentNamespace(VoidNamespace.INSTANCE);
> backend.setCurrentKey(i);
> state.update(i);
>
> futureList.add(runSnapshotAsync(backend.snapshot(checkpointID++,
> System.currentTimeMillis(), streamFactory,
> CheckpointOptions.forCheckpointWithDefaultLocation())));
> }
> for (Future future : futureList) {
> future.get();
> }
> } catch (Exception e) {
> fail();
> } finally {
> backend.dispose();
> }
> }
> protected Future<?> runSnapshotAsync(
> RunnableFuture<SnapshotResult<KeyedStateHandle>>
> snapshotRunnableFuture) throws Exception {
> if (!snapshotRunnableFuture.isDone()) {
> return Executors.newFixedThreadPool(5).submit(() -> {
> try {
> snapshotRunnableFuture.run();
> snapshotRunnableFuture.get();
> } catch (Exception e) {
> e.printStackTrace();
> fail();
> }
> });
> }
> return null;
> }
> {code}
> Place the above code in `StateBackendTestBase` and run
> `AsyncMemoryStateBackendTest`, it will get the follows exception
> {code}
> java.util.concurrent.ExecutionException: java.lang.NullPointerException
> at java.util.concurrent.FutureTask.report(FutureTask.java:122)
> at java.util.concurrent.FutureTask.get(FutureTask.java:192)
> at
> org.apache.flink.runtime.state.AsyncMemoryStateBackendTest.lambda$runSnapshotAsync$0(AsyncMemoryStateBackendTest.java:85)
> at
> java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
> at java.util.concurrent.FutureTask.run(FutureTask.java:266)
> at
> java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
> at
> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
> at java.lang.Thread.run(Thread.java:745)
> Caused by: java.lang.NullPointerException
> at
> org.apache.flink.runtime.state.heap.HeapKeyedStateBackend$HeapSnapshotStrategy$1.performOperation(HeapKeyedStateBackend.java:716)
> at
> org.apache.flink.runtime.state.heap.HeapKeyedStateBackend$HeapSnapshotStrategy$1.performOperation(HeapKeyedStateBackend.java:662)
> at
> org.apache.flink.runtime.io.async.AbstractAsyncCallableWithResources.call(AbstractAsyncCallableWithResources.java:75)
> at java.util.concurrent.FutureTask.run(FutureTask.java:266)
> at
> org.apache.flink.runtime.state.AsyncMemoryStateBackendTest.lambda$runSnapshotAsync$0(AsyncMemoryStateBackendTest.java:84)
> ... 5 more
> java.util.concurrent.ExecutionException: java.lang.NullPointerException
> at java.util.concurrent.FutureTask.report(FutureTask.java:122)
> at java.util.concurrent.FutureTask.get(FutureTask.java:192)
> at
> org.apache.flink.runtime.state.AsyncMemoryStateBackendTest.lambda$runSnapshotAsync$0(AsyncMemoryStateBackendTest.java:85)
> at
> java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
> at java.util.concurrent.FutureTask.run(FutureTask.java:266)
> at
> java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
> at
> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
> at java.lang.Thread.run(Thread.java:745)
> Caused by: java.lang.NullPointerException
> at
> org.apache.flink.runtime.state.heap.HeapKeyedStateBackend$HeapSnapshotStrategy$1.performOperation(HeapKeyedStateBackend.java:716)
> at
> org.apache.flink.runtime.state.heap.HeapKeyedStateBackend$HeapSnapshotStrategy$1.performOperation(HeapKeyedStateBackend.java:662)
> at
> org.apache.flink.runtime.io.async.AbstractAsyncCallableWithResources.call(AbstractAsyncCallableWithResources.java:75)
> at java.util.concurrent.FutureTask.run(FutureTask.java:266)
> at
> org.apache.flink.runtime.state.AsyncMemoryStateBackendTest.lambda$runSnapshotAsync$0(AsyncMemoryStateBackendTest.java:84)
> ... 5 more
> {code}
--
This message was sent by Atlassian JIRA
(v7.6.3#76005)
