prashantwason opened a new pull request, #19790:
URL: https://github.com/apache/hudi/pull/19790
**Describe the issue this Pull Request addresses**
DistributedRegistry is a JVM-wide singleton (cached in
Registry.REGISTRY_MAP) and a Spark AccumulatorV2. When executor metrics are
enabled (hoodie.metrics.executor.enable=true) and multiple Hudi write clients
are created within the same JVM (e.g. batch frameworks processing multiple
tables sequentially), the cached DistributedRegistry instance retains metadata
set from a prior SparkContext registration.
On a subsequent initRegistry() call:
- AccumulatorV2.isRegistered() returns false — the id is no longer in the
current AccumulatorContext
- The guard in DistributedRegistry.register() lets the call through
- AccumulatorV2.register() throws IllegalStateException("Cannot register an
Accumulator twice") because metadata is non-null
This crashes the write with HoodieException: Failed to instantiate Metadata
table.
**Summary and Changelog**
Fix DistributedRegistry.register() to handle the stale-singleton case where
the accumulator was registered to a previous SparkContext that no longer exists.
- DistributedRegistry.register(): on IllegalStateException, create a fresh
AccumulatorV2, copy counters from the stale instance, register the fresh
instance, and swap it into Registry.REGISTRY_MAP. Changed return type from void
to DistributedRegistry so callers receive the potentially-replaced instance.
- SparkHoodieBackedTableMetadataWriter.initRegistry(): use the returned
registry from register().
- SparkHoodieBackedTableMetadataWriterTableVersionSix.initRegistry(): same.
- HoodieSparkEngineContext.getMetricRegistry(): same.
- TestDistributedRegistry: added testRegisterIdempotent and
testRegisterHandlesStaleAccumulator.
**Impact**
No public API or user-facing feature change. No performance impact — the fix
only alters behavior in the error path (stale accumulator from a dead
SparkContext). The normal registration path is unchanged.
**Risk Level**
Low. The catch block only fires when AccumulatorV2.register() throws
IllegalStateException, which is the exact crash this fixes. The fresh instance
is functionally identical to the original, with counters preserved.
**Documentation Update**
None. No new configs or user-facing changes.
**Contributor's checklist**
- [x] Read through contributor's guide
- [x] Enough context is provided in the sections above
- [x] Adequate tests were added if applicable
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