[PR] Fix schema partition lookup during ConfigNode removal [iotdb]

["d-wang-commit (via GitHub)" <gi...@apache.org>]

d-wang-commit opened a new pull request, #18686:
URL: https://github.com/apache/iotdb/pull/18686

   ## Description
   
   ### Return retryable status during ConfigNode removal
   
   A ConfigNode can still accept requests on existing connections after its local ConfigRegion has been deleted and before its process stops. The slot-based schema partition lookup previously read consensus state without checking leadership, returning EXECUTE_STATEMENT_ERROR (301) when the group no longer existed. This response does not trigger the ConfigNode client's redirection retry.
   
   Call confirmLeader() before reading schema partitions and return its status immediately when the node cannot serve the request. A removed node can return REDIRECTION_RECOMMEND (400) without a leader address, allowing the existing client retry logic to select another ConfigNode.
   
   ### Tests
   
   - UT: No unit tests added or modified. The regression is covered with real ConfigNode processes and the production ConfigNodeClient implementation.
   - IT: Added IoTDBRemoveConfigNodeSchemaPartitionIT with two scenarios: delete a follower's local ConfigRegion while keeping its process and connections alive, then verify redirection and client recovery; remove the current leader while continuously inserting new devices and checking row counts on existing partitions.
   - Validation: the targeted Maven reactor build and both IT cases passed locally (2 tests, 0 failures, 0 errors). The baseline run of the deleted-ConfigRegion case failed with status 301 instead of the expected 400.
   
   ### Side effects and risks
   
   The tree-model schema partition lookup, getSchemaPartitionTable -> ConfigManager.getSchemaPartition(PathPatternTree, boolean), already calls confirmLeader(). This change adds the same guard to the corresponding table-model lookup, getSchemaPartitionTableWithSlots -> ConfigManager.getSchemaPartition(Map<String, List<TSeriesPartitionSlot>>), making the two entry paths consistent.
   
   The guard also precedes the empty-database-map fast return. Requests reaching a follower or an unready leader may incur redirection or readiness-check latency. This reuses the existing leadership checks and client retry behavior; it changes no RPC schema, configuration, or persisted format. The ITs cover recovery and row counts, but do not establish latency bounds or exhaust all concurrent removal interleavings. No separate user documentation was added for this internal RPC guard.
   
   <hr>
   
   This PR has:
   - [x] been self-reviewed.
   - [x] added comments explaining the "why" and the intent of the code wherever would not be obvious for an unfamiliar reader.
   - [x] added integration tests.
   - [x] been tested in a test IoTDB cluster.
   
   <hr>
   
   ##### Key changed/added classes (or packages if there are too many classes) in this PR
   
   - ConfigManager: check leadership before the slot-based schema partition lookup.
   - IoTDBRemoveConfigNodeSchemaPartitionIT: cover client recovery after local ConfigRegion deletion and table read/write continuity during leader removal.
   


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Re: [PR] Fix schema partition lookup during ConfigNode removal [iotdb]

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

CRZbulabula merged PR #18686:
URL: https://github.com/apache/iotdb/pull/18686


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