[I] MySQL JDBC catalog does not recover from a dropped connection [iceberg]

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

bharos opened a new issue, #17829:
URL: https://github.com/apache/iceberg/issues/17829

   ### Apache Iceberg version
   
   1.11.0 (latest release)
   
   ### Query engine
   
   Other
   
   ### Please describe the bug 🐞
   
   When a MySQL-backed `JdbcCatalog` connection is dropped by the server (for example an idle connection closed at `wait_timeout`), the pool does not recover it:
   
   ```
   UncheckedSQLException: Failed to execute exists query: SELECT ... FROM iceberg_tables ...
     Caused by: com.mysql.cj.jdbc.exceptions.CommunicationsException: Communications link failure
       Caused by: java.net.SocketException: Broken pipe
   ```
   
   The failure does not clear on the next call. `ClientPoolImpl.release` returns the client with `addFirst`, so the dead connection goes back to the head of the pool and is handed to the next caller.
   
   `JdbcClientPool` already reconnects on connection failures, but only for `SQLTransientException` and the SQLSTATEs in `COMMON_RETRYABLE_CONNECTION_SQL_STATES`. MySQL's `CommunicationsException` extends `SQLRecoverableException` — a sibling of `SQLTransientException`, not a subtype — and reports SQLSTATE `08S01`, which is not in that set. Neither check matches, so no reconnect is attempted.
   
   Same symptom as #14317.
   
   Proposed fix: treat `SQLRecoverableException` as retryable. The JDBC contract for that type is that recovery requires closing the connection and obtaining a new one, which is what `JdbcClientPool.reconnect` does. Adding `08S01` to the default SQLSTATEs would fix MySQL only.
   
   On existing releases, `retryable_status_codes=08S01` works as a workaround.
   
   PR: #17828
   


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