[CC5] CNDB-15558: ULID-based SSTable ID generation can fail with an NPE #2178
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ULID-based SSTable ID generation can fail with an NPE when generating a new ID. The root cause is that the underlying ULID generator can generate an empty Optional when the clock is moved backwards to before the previously generated ID or in certain rare overflow conditions when timestamp collides. If it's our first time through the generation loop, we prematurely exit with a null newVal. Top of the error stack: ``` java.lang.NullPointerException at org.apache.cassandra.utils.TimeUUID.approximateFromULID(TimeUUID.java:58) at org.apache.cassandra.io.sstable.ULIDBasedSSTableId.<init>(ULIDBasedSSTableId.java:52) at org.apache.cassandra.io.sstable.ULIDBasedSSTableId$Builder.lambda$generator$0(ULIDBasedSSTableId.java:129) ``` This can cause a flush to fail. Continue looping until newVal gets a value. The loop can spin until the corrected time catches up to the time of the most recently used ULID generation ID. This should be a short duration in a healthy cluster without large time corrections from sync. Tests are added in ULIDBasedSSTableIdGeneratorTest A package-protected constructor is introduced for ULIDBasedSSTableIdGeneratorTest.testGeneratorRetryOnEmptyOptional() Cassandra Applicability: upstream doesn't have ULIDBasedSSTableId (and won't because CASSANDRA-17048).
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jkni
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Dec 18, 2025
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LGTM. Can you re-trigger CI and I'll come back and approve once that looks good?
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https://github.com/riptano/cndb/issues/15558
What is the issue
ULID-based SSTable ID generation can fail with an NPE when generating a new ID. The root cause is that the underlying ULID generator can generate an empty Optional when the clock is moved backwards to before the previously generated ID or in certain rare overflow conditions when timestamp collides. If it's our first time through the generation loop, we prematurely exit with a null newVal.
Top of the error stack:
This can cause a flush to fail.
What does this PR fix and why was it fixed
Continue looping until newVal gets a value. The loop can spin until the corrected time catches up to the time of the most recently used ULID generation ID. This should be a short duration in a healthy cluster without large time corrections from sync.