JackieTien97 opened a new pull request, #16604: URL: https://github.com/apache/iotdb/pull/16604
This pull request introduces support for a new read consistency level, `follower_read`, across the IoTDB codebase. The changes ensure that configuration, logic, and documentation now recognize and correctly handle this new option alongside the existing `strong` and `weak` levels. **Read Consistency Level Enhancements:** * Added `FOLLOWER_READ` to the `ReadConsistencyLevel` enum in `ReadConsistencyLevel.java`, allowing the system to use follower replicas for read operations. * Updated the configuration logic in `ConfigNodeDescriptor.java` and `IoTDBConfig.java` to accept and validate the new `follower_read` value, throwing exceptions for unknown values. [[1]](diffhunk://#diff-3ed021394fbf9a40c9ad48c24dfb3ba90ebb20aba5bdcf9a7763ebe0cca5e70dL362-R364) [[2]](diffhunk://#diff-30d3dc10c256a0068e3b87dd128011b653b4a8ecd0f0bf1149979022b5d92ea7L3345-R3351) * Enhanced the planner logic in `AbstractFragmentParallelPlanner.java` to select follower replicas when `FOLLOWER_READ` is specified, ensuring the leader is skipped and a follower is chosen based on session ID. * Updated the configuration template in `iotdb-system.properties.template` to document the new `follower_read` option for users. **Refactoring and Logic Separation:** * Refactored the data node selection logic in `AbstractFragmentParallelPlanner.java` by extracting target index determination into a separate method, improving readability and maintainability. Supposing we have a 3C3D cluster and data replica number is set to 3, we execute the following sqls to prepare data: ``` create database test; use test; create table t1(device_id STRING TAG, s1 float); insert into t1 values(now(),'d1', 1.0); ``` Before this pr, if we do `select * from t1;` query, the query will always be routed to leader: <img width="2900" height="1800" alt="f374fca129e9c9da5bb8f5e86e53384f" src="https://github.com/user-attachments/assets/cbad4ec8-3486-4c6c-afbe-cbe571ac1043"; /> After this pr, if we set `read_consistency_level=follower_read` and then restart the cluster, then the above query will always be routed to any follower: <img width="2748" height="1468" alt="edcf2ad9bdf44cb525d6ef196c171704" src="https://github.com/user-attachments/assets/34106086-bd3a-4b9d-8497-de701bc06de0"; /> -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
