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https://issues.apache.org/jira/browse/NIFI-15917?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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David Handermann resolved NIFI-15917.
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Fix Version/s: 2.10.0
Resolution: Fixed
> If an extension stores Local state and then modifies the Map, it could lead
> to a corrupted stored state
> -------------------------------------------------------------------------------------------------------
>
> Key: NIFI-15917
> URL: https://issues.apache.org/jira/browse/NIFI-15917
> Project: Apache NiFi
> Issue Type: Bug
> Components: Core Framework
> Reporter: Mark Payne
> Assignee: Mark Payne
> Priority: Major
> Fix For: 2.10.0
>
> Time Spent: 1h
> Remaining Estimate: 0h
>
> If an extension does something like this:
> {code:java}
> private final Map<String, String> state = new ConcurrentHashMap<>();
> private final AtomicLong counter = new AtomicLong(0L);
> public void onTrigger(...) {
> state.put("invocation", String.valueOf(counter.getAndIncrement()));
> session.setState(state);
> } {code}
> What gets written to the state journal when the session commit is performed
> is correct.
> However, at some time later, when the WriteAhead Repository checkpoints, it
> uses a reference to that same `state` Map rather than a defensive copy. So
> the checkpoint may have a very different value than what was written to the
> journal.
> Further, if timing is just write, it may write out the number of entries as
> `n` and then write out `m` different entries. For example, if the `onTrigger`
> method were to call `state.put("secondKey", "two");` while the checkpoint is
> occurring, it could end up writing the fact that the map has 1 key
> (`invocation`) followed by writing 2 entries (`invocation` and `secondKey`)
> which would cause corruption.
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