[I] $binlog source may fail on interleaved updates from multiple log splits [fluss]

["luoyuxia (via GitHub)" <gi...@apache.org>]

luoyuxia opened a new issue, #2879:
URL: https://github.com/apache/fluss/issues/2879

   ## Search before asking
   - [x] I searched in the issues and found nothing similar.
   
   ## Fluss version
   main (development)
   
   ## Please describe the bug 🐞
   When reading a `$binlog` table, the Flink source can fail with the following exception if one `SourceReader` processes records from multiple log splits and update events are interleaved across splits:
   
   ```text
   Cause: Received UPDATE_AFTER (+U) without a preceding UPDATE_BEFORE (-U) record. This indicates a corrupted log sequence.
   ```
   
   The root cause is that `BinlogRowConverter` keeps only one global pending `UPDATE_BEFORE` record. This works if records are strictly processed from a single split, but it breaks once the same reader interleaves records from different bucket log splits.
   
   A problematic sequence looks like this:
   
   1. split A emits `UPDATE_BEFORE`
   2. split B emits `UPDATE_BEFORE`
   3. split B emits `UPDATE_AFTER`
   4. split A emits `UPDATE_AFTER`
   
   With a single global pending buffer:
   
   - split B's `UPDATE_BEFORE` overwrites split A's pending state;
   - split B's `UPDATE_AFTER` consumes that global state;
   - split A's `UPDATE_AFTER` no longer finds its matching `UPDATE_BEFORE` and throws the exception above.
   
   Depending on the exact interleaving, this can also temporarily pair the wrong before/after rows across splits before eventually failing.
   
   This is especially relevant for `$binlog` on primary key tables with multiple buckets, where one reader may own multiple log splits at the same time.
   
   ### Expected behavior
   `UPDATE_BEFORE` / `UPDATE_AFTER` pairing should be isolated per split, so interleaving records from different splits does not corrupt update reconstruction.
   
   ### Actual behavior
   The pairing state is shared across splits, which can corrupt update reconstruction and fail the source task with:
   
   ```text
   Received UPDATE_AFTER (+U) without a preceding UPDATE_BEFORE (-U) record.
   ```
   
   ### How to reproduce
   A minimal reproduction is:
   
   1. Create a primary key table with multiple buckets.
   2. Read from the corresponding `$binlog` table with the Flink source.
   3. Make one reader consume multiple log splits.
   4. Produce interleaved updates from different buckets/splits in the order `A:-U -> B:-U -> B:+U -> A:+U`.
   
   The reader can then fail because the pending `UPDATE_BEFORE` state is overwritten by another split.
   
   ## Solution
   Use split-scoped buffering for update pairing instead of a single global pending record.
   
   Concretely:
   
   1. change `BinlogRowConverter` from a single pending `UPDATE_BEFORE` field to a `Map<splitId, LogRecord>`;
   2. pass the current split id through the deserialization path before converting a log record;
   3. merge `UPDATE_BEFORE` / `UPDATE_AFTER` only within the same split;
   4. add regression tests for interleaved cross-split update sequences, ideally both at the converter level and through the emitter/deserializer path.
   
   This keeps `$binlog` update reconstruction correct even when multiple splits are processed by the same source reader.
   
   ## Are you willing to submit a PR?
   - [ ] I'm willing to submit a PR!
   


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Re: [I] $binlog source may fail on interleaved updates from multiple log splits [fluss]

["luoyuxia (via GitHub)" <gi...@apache.org>]

luoyuxia closed issue #2879: $binlog source may fail on interleaved updates from multiple log splits
URL: https://github.com/apache/fluss/issues/2879


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Re: [I] $binlog source may fail on interleaved updates from multiple log splits [fluss]

["luoyuxia (via GitHub)" <gi...@apache.org>]

luoyuxia commented on issue #2879:
URL: https://github.com/apache/fluss/issues/2879#issuecomment-4505855010

   Closed via #3149 


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