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https://issues.apache.org/jira/browse/CASSANDRA-21217?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18108777#comment-18108777
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Stefan Miklosovic commented on CASSANDRA-21217:
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[~nivy] something to look at?
> Race condition between hints and decommision
> --------------------------------------------
>
> Key: CASSANDRA-21217
> URL: https://issues.apache.org/jira/browse/CASSANDRA-21217
> Project: Apache Cassandra
> Issue Type: Bug
> Reporter: Gil Ganz
> Priority: Normal
> Labels: HintedHandoff, decommision
> Time Spent: 10m
> Remaining Estimate: 0h
>
> I am running decommission on 4.1.5 cluster, and decommission fails to
> complete due to error regarding hints. It runs for quite some time, streaming
> what appears to be all data, but then fails due to this error (which happened
> quite early in the decommission process).
> I got this in 3 separate cases (this is an env that is spread across the
> world, so network hiccups are common).
> I was able to overcome this by setting transfer_hints_on_decommission: false,
> but I think the code that handles that hints in the decommision path should
> not fail on missing file, it can just throw a warning, and not require me to
> not transfer any hint.
> INFO [NonPeriodicTasks:1] 2026-03-12 18:13:47,148
> StreamResultFuture.java:252 - [Stream
> #24728df0-1e20-11f1-be78-9bd75fd01983|#24728df0-1e20-11f1-be78-9bd75fd01983]
> All sessions completed
> ERROR [RMI TCP Connection(3338753)-127.0.0.1] 2026-03-12 18:13:47,149
> StorageService.java:5017 - Error while decommissioning node
> java.lang.RuntimeException: java.nio.file.NoSuchFileException:
> /var/lib/cassandra/data/disk1/hints/5da9d583-259e-425f-a0ad-18b7e744dabc-1744041563101-2.hints
> at
> org.apache.cassandra.io.util.ChannelProxy.openChannel(ChannelProxy.java:54)
> at
> org.apache.cassandra.io.util.ChannelProxy.<init>(ChannelProxy.java:65)
> at
> org.apache.cassandra.hints.ChecksummedDataInput.open(ChecksummedDataInput.java:76)
> at org.apache.cassandra.hints.HintsReader.open(HintsReader.java:78)
> at
> org.apache.cassandra.hints.HintsDispatcher.create(HintsDispatcher.java:79)
> at
> org.apache.cassandra.hints.HintsDispatchExecutor$DispatchHintsTask.deliver(HintsDispatchExecutor.java:290)
> at
> org.apache.cassandra.hints.HintsDispatchExecutor$DispatchHintsTask.dispatch(HintsDispatchExecutor.java:277)
> at
> org.apache.cassandra.hints.HintsDispatchExecutor$DispatchHintsTask.dispatch(HintsDispatchExecutor.java:255)
> at
> org.apache.cassandra.hints.HintsDispatchExecutor$DispatchHintsTask.run(HintsDispatchExecutor.java:234)
> at
> java.base/java.util.stream.ForEachOps$ForEachOp$OfRef.accept(ForEachOps.java:183)
> at
> java.base/java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:195)
> at
> java.base/java.util.concurrent.ConcurrentHashMap$ValueSpliterator.forEachRemaining(ConcurrentHashMap.java:3603)
> at
> java.base/java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:484)
> at
> java.base/java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:474)
> at
> java.base/java.util.stream.ForEachOps$ForEachOp.evaluateSequential(ForEachOps.java:150)
> at
> java.base/java.util.stream.ForEachOps$ForEachOp$OfRef.evaluateSequential(ForEachOps.java:173)
> at
> java.base/java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
> at
> java.base/java.util.stream.ReferencePipeline.forEach(ReferencePipeline.java:497)
> at
> org.apache.cassandra.hints.HintsDispatchExecutor$TransferHintsTask.transfer(HintsDispatchExecutor.java:196)
> at
> org.apache.cassandra.hints.HintsDispatchExecutor$TransferHintsTask.run(HintsDispatchExecutor.java:169)
> Proposed fix
> 1. Catch missing file in {{deliver()}} ({{{}HintsDispatchExecutor.java{}}}
> ~line 287)
> Wrap the {{HintsDispatcher.create()}} call to catch {{RuntimeException}}
> caused by {{{}NoSuchFileException{}}}. If the file is gone, the hints were
> already successfully
> dispatched — delete the descriptor from the store and return {{{}true{}}}.
> \{code:java}
> private boolean deliver(HintsDescriptor descriptor, InetAddressAndPort
> address)
> {
> File file = descriptor.file(hintsDirectory);
> if (!file.exists())
> {
> logger.info("Hints file {} was already dispatched, skipping", file);
> store.cleanUp(descriptor);
> return true;
> }
> // ... existing code
> }
> \{code}
> Note: a simple {{file.exists()}} pre-check narrows the window but does not
> eliminate the TOCTOU race. The {{try-catch}} around
> {{HintsDispatcher.create()}} is still
> needed as a backstop:
> \{code:java}
> try (HintsDispatcher dispatcher = HintsDispatcher.create(file, rateLimiter,
> address, descriptor.hostId, shouldAbort))
>
> { // ... existing dispatch logic }
> catch (RuntimeException e)
> {
> if (Throwables.getRootCause(e) instanceof NoSuchFileException)
> {
> logger.info("Hints file {} disappeared during dispatch, treating as
> already dispatched", file);
> store.cleanUp(descriptor);
> return true;
> }
> throw e;
> }
> \{code}
> 2. Prevent the race in {{transferHints()}} ({{{}HintsService.java{}}} ~line
> 440)
> After {{completeDispatchBlockingly()}} at line 444, call
> {{pauseDispatch()}} again before starting the transfer at line 446. This
> prevents {{HintsDispatchTrigger}}
> from scheduling new normal dispatch tasks that race with the transfer:
> \{code:java}
> // current code at line 441:
> resumeDispatch();
> catalog.stores().forEach(dispatchExecutor::completeDispatchBlockingly);
> // add:
> pauseDispatch();
> return dispatchExecutor.transfer(catalog, hostIdSupplier);
> \{code}
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