XuQianJin-Stars opened a new pull request, #3286:
URL: https://github.com/apache/fluss/pull/3286
TieringSourceEnumerator now acquires a KV snapshot lease for all
TieringSnapshotSplits before they are assigned to readers, and releases the
lease when the table finishes or fails tiering, or when a reader failover
returns the splits. A best-effort `dropLease` is also performed on enumerator
close. This prevents the Fluss server from cleaning up snapshots that the
tiering job still depends on.
One lease id per tiering job (UUID-based) is reused across tables and
persisted into `TieringSourceEnumeratorState` so that it survives enumerator
restore instead of leaking orphan leases. The lease uses a fixed 1-day duration
that is implicitly renewed by every `acquireSnapshots` call, and
`UnsupportedVersionException` from older Fluss servers is downgraded to a
warning to keep backward compatibility.
### Purpose
Linked issue: close #2898
Before this change, the tiering job only read Fluss KV snapshots without
holding any lease on them. A long-running tiering job could therefore race with
the server-side snapshot GC: the server may clean up a snapshot that is still
being / about to be consumed by the tiering `SourceReader`, causing tiering
failures or data loss on the lake side.
This PR makes `TieringSource` hold a KV snapshot lease for the full
lifecycle of each snapshot split it hands out, so that the Fluss server will
not reclaim those snapshots while tiering is in progress.
### Brief change log
- `TieringSourceEnumerator`
- Generate one `kvSnapshotLeaseId` per tiering job (UUID-based) and reuse
it across all tables.
- Before assigning any `TieringSnapshotSplit` to a reader, call
`acquireSnapshots(leaseId, snapshots, 1 day)` on the admin / gateway client to
acquire a lease covering all snapshot splits of the table.
- Track in-flight leased snapshots per table; release the lease
(`releaseSnapshots`) when the table finishes tiering, fails tiering, or when a
reader failover returns the splits back to the enumerator.
- On enumerator `close()`, best-effort `dropLease(leaseId)` to release
everything still held by this job.
- Downgrade `UnsupportedVersionException` (old server) to a warning log,
so the tiering job keeps working against older Fluss servers without the lease
API.
- `TieringSourceEnumeratorState` + `TieringSourceEnumeratorStateSerializer`
- Persist `kvSnapshotLeaseId` into the enumerator checkpoint state (new
serializer version, backward compatible with the previous version).
- `TieringSource`
- On `restoreEnumerator`, reuse the persisted `kvSnapshotLeaseId` from the
checkpoint so the recovered enumerator does not generate a new UUID and leak
the previous lease.
### Tests
- `TieringSourceEnumeratorTest`
- New cases covering: lease is acquired before snapshot splits are
assigned; lease is released on table finish / fail / reader failover;
`dropLease` is invoked on enumerator close; enumerator works gracefully when
the server returns `UnsupportedVersionException`.
- `TieringSourceEnumeratorStateSerializerTest`
- Round-trip tests for the new `kvSnapshotLeaseId` field, plus a
backward-compatibility case that deserializes a state written by the previous
serializer version.
- `mvn clean verify` passes locally for the affected modules.
### API and Format
- No public user-facing API change.
- `TieringSourceEnumeratorState` checkpoint format is extended with a new
`kvSnapshotLeaseId` field. The serializer version is bumped and older
checkpoints remain readable (the field defaults to a freshly generated UUID on
restore from old state).
- No storage / wire format change on the Fluss server side; this PR only
consumes the existing `acquireSnapshots` / `releaseSnapshots` / `dropLease`
admin APIs.
### Documentation
- No new user-facing feature or configuration option is introduced, so no
documentation update is required.
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