[BUG] ConcurrentModificationException thrown while calling the decide function

Is there an existing issue for this?

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SDK Version

5.0.0

Current Behavior

Crash in the optimizely SDK:

Stack trace:

          Caused by java.util.ConcurrentModificationException:
       at java.util.HashMap$HashIterator.nextNode(HashMap.java:1603)
       at java.util.HashMap$EntryIterator.next(HashMap.java:1636)
       at java.util.HashMap$EntryIterator.next(HashMap.java:1634)
       at java.util.HashMap.putMapEntries(HashMap.java:518)
       at java.util.HashMap.<init>(HashMap.java:491)
       at com.optimizely.ab.OptimizelyUserContext.<init>(OptimizelyUserContext.java:72)
       at com.optimizely.ab.OptimizelyUserContext.copy(OptimizelyUserContext.java:106)
       at com.optimizely.ab.OptimizelyUserContext.decide(OptimizelyUserContext.java:143)
       at com.optimizely.ab.OptimizelyUserContext.decide(OptimizelyUserContext.java:153)

Device breakdown:

Data insights:

Expected Behavior

No crash.

Steps To Reproduce

We have been unable to deterministically reproduce this issue.
This is affecting a small percentage of our user base, around 3%

Link

No response

Logs

Nothing relevant outside of the stacktrace already shared

Severity

Affecting users

Workaround/Solution

As this is a side-effect of calling the userContext.decide() There is no workaround that still results in the user receiving a valid decision.

Recent Change

No response

Conflicts

No response

Start with OptimizelyUserContext.java, especially the copy and decide methods named in the stack trace. Investigate concurrent calls to userContext.decide() and the HashMap construction that throws ConcurrentModificationException; reproduction is currently nondeterministic. Done means concurrent decide calls no longer crash and still return valid decisions.