Cancel a replica task

The execution of current disaster recovery tasks is subject to a limitation: except for migration replica tasks, a tenant's log stream can only allow one replica task to be executed at a time. This means some urgent tasks may need to wait until the ongoing task is completed before they can be executed. If you need to prioritize an urgent task, you can use the ALTER SYSTEM CANCEL REPLICA TASK command to manually cancel the running replica task.

Limitations

• The current version only supports canceling two types of replica tasks: supplement replica and migration replica tasks.

  Note

  In the current version, for a replica migration task caused by unit migration, if the destination side has no units left, the system automatically cancels the corresponding replica migration task; manual cancellation is not required.

• The sys tenant can cancel replica tasks for all tenants. User tenants can only cancel replica tasks for their own tenant.

Prerequisites

• Before canceling a replica task, ensure the current user has the ALTER SYSTEM privilege; otherwise, the ALTER SYSTEM CANCEL REPLICA TASK command cannot be executed.

• Before querying views, ensure the current user has the SELECT privilege on the following views; otherwise, the relevant information cannot be queried.

  • DBA_OB_LS_REPLICA_TASKS/ CDB_OB_LS_REPLICA_TASKS

  • DBA_OB_LS_REPLICA_TASK_HISTORY/ CDB_OB_LS_REPLICA_TASK_HISTORY

Procedure

Assume there is currently a tenant1 tenant, and an R replica of its log stream 1001 is undergoing a migration task. At this moment, a failure occurs in the current cluster, and it is urgently necessary to supplement an F replica on an available machine to ensure high availability. However, because the data volume of the migrating R replica is very large, the task is taking a long time to complete, preventing the timely execution of the urgent maintenance operation to supplement the F replica. In this case, maintenance personnel can refer to this document to manually cancel the disaster recovery task for the migrating R replica, thereby prioritizing the execution of some urgent maintenance operations.

1. Log in to the tenant corresponding to the cluster.

   A connection example is as follows:

   obclient -h172.30.xxx.xxx -P2883 -uroot@tenant1#obdemo -pxxxx -A
   

   For more detailed instructions on connecting to a database, see Overview of database connections (MySQL-compatible mode) and Overview of database connections (Oracle-compatible mode).

2. View the currently running disaster recovery tasks.

   • System tenant

     obclient [oceanbase]> SELECT * FROM oceanbase.CDB_OB_LS_REPLICA_TASKS\G
     

     For detailed descriptions of the fields in the CDB_OB_LS_REPLICA_TASKS view, see CDB_OB_LS_REPLICA_TASKS.

   • User tenant

     MySQL-compatible mode

     Oracle-compatible mode

     Execute the following statement in MySQL-compatible mode:

     obclient [oceanbase]> SELECT * FROM oceanbase.DBA_OB_LS_REPLICA_TASKS\G
     

     Execute the following statement in Oracle-compatible mode:

     obclient [SYS]> SELECT * FROM SYS.DBA_OB_LS_REPLICA_TASKS\G
     

     The following example shows the query result:

     *************************** 1. row ***************************
                           LS_ID: 1001
                       TASK_TYPE: MIGRATE REPLICA
                         TASK_ID: Y13CE64586BD4-000610C5F3EDBBCB-0-0
                     TASK_STATUS: INPROGRESS
                        PRIORITY: LOW
           TARGET_REPLICA_SVR_IP: 100.xx.xxx.002
         TARGET_REPLICA_SVR_PORT: 5072
     TARGET_PAXOS_REPLICA_NUMBER: 2
             TARGET_REPLICA_TYPE: FULL
           SOURCE_REPLICA_SVR_IP: 100.xx.xxx.003
         SOURCE_REPLICA_SVR_PORT: 5073
     SOURCE_PAXOS_REPLICA_NUMBER: 2
             SOURCE_REPLICA_TYPE: FULL
              DATA_SOURCE_SVR_IP: 100.xx.xxx.003
            DATA_SOURCE_SVR_PORT: 5073
                       IS_MANUAL: FALSE
                TASK_EXEC_SVR_IP: 100.xx.xxx.002
              TASK_EXEC_SVR_PORT: 5072
                     CREATE_TIME: 2024-02-07 15:23:04
                      START_TIME: 2024-02-07 15:23:04
                     MODIFY_TIME: 2024-02-07 15:23:04
                         COMMENT: migrate replica due to unit group not match
                  CONFIG_VERSION: 
     1 row in set
     

     The query result indicates that a disaster recovery task with TASK_TYPE set to MIGRATE REPLICA is in progress, and its TASK_ID is recorded.

     For more information about the columns in the DBA_OB_LS_REPLICA_TASKS view, see DBA_OB_LS_REPLICA_TASKS.

3. Execute the command to cancel the replica task.

   The statement is as follows:

   ALTER SYSTEM CANCEL REPLICA TASK TASK_ID [=] 'task_id' [TENANT [=] 'tenant_name'];
   

   Usage instructions:

   • task_id: The TASK_ID of the replica task to be canceled.

   • tenant_name: Specifies the tenant to operate on. The system tenant can specify other tenants, while a user tenant can only specify itself. If the tenant to operate on is not explicitly specified, the default tenant name is the current tenant. This statement does not support using all, all_user, or all_meta to specify all tenants, user tenants, or all Meta tenants.

   • This statement can only cancel one disaster recovery task per tenant at a time.

   Example:

   obclient> ALTER SYSTEM CANCEL REPLICA TASK TASK_ID = 'Y13CE64586BD4-000610C5F3EDBBCB-0-0';
   

4. Check the cancellation result of the replica task.

   • System tenant

     obclient [oceanbase]> SELECT * FROM oceanbase.CDB_OB_LS_REPLICA_TASK_HISTORY WHERE TASK_ID = 'Y13CE64586BD4-000610C5F3EDBBCB-0-0'\G
     

     For more information about the columns in the CDB_OB_LS_REPLICA_TASK_HISTORY view, see CDB_OB_LS_REPLICA_TASK_HISTORY.

   • User tenant

     MySQL-compatible mode

     Oracle-compatible mode

     In MySQL-compatible mode, execute the following statement:

     obclient [oceanbase]> SELECT * FROM oceanbase.DBA_OB_LS_REPLICA_TASK_HISTORY WHERE TASK_ID = 'Y13CE64586BD4-000610C5F3EDBBCB-0-0'\G
     

     In Oracle-compatible mode, execute the following statement:

     obclient [SYS]> SELECT * FROM SYS.DBA_OB_LS_REPLICA_TASK_HISTORY WHERE TASK_ID = 'Y13CE64586BD4-000610C5F3EDBBCB-0-0'\G
     

     The following example shows the query result:

     *************************** 1. row ***************************
                           LS_ID: 1001
                       TASK_TYPE: MIGRATE REPLICA
                         TASK_ID: Y13CE64586BD4-000610C5F3EDBBCB-0-0 
                     TASK_STATUS: CANCELED
                        PRIORITY: LOW
           TARGET_REPLICA_SVR_IP: 100.xx.xxx.002
         TARGET_REPLICA_SVR_PORT: 5072
     TARGET_PAXOS_REPLICA_NUMBER: 2
             TARGET_REPLICA_TYPE: FULL
           SOURCE_REPLICA_SVR_IP: 100.xx.xxx.003
         SOURCE_REPLICA_SVR_PORT: 5073
     SOURCE_PAXOS_REPLICA_NUMBER: 2
             SOURCE_REPLICA_TYPE: FULL
              DATA_SOURCE_SVR_IP: 100.xx.xxx.003
            DATA_SOURCE_SVR_PORT: 5073
                       IS_MANUAL: FALSE
                TASK_EXEC_SVR_IP: 100.xx.xxx.002
              TASK_EXEC_SVR_PORT: 5072
                     CREATE_TIME: 2024-02-07 15:54:35
                      START_TIME: 2024-02-07 15:54:31
                     MODIFY_TIME: 2024-02-07 15:54:35
                     FINISH_TIME: 2024-02-07 15:54:34
                  EXECUTE_RESULT: ret:-4072, OB_CANCELED; elapsed:4109659; comment:[storage] receive task reply from storage rpc;
                         COMMENT: migrate replica due to unit not match
                  CONFIG_VERSION: 
     1 row in set
     

     In the query result, if TASK_STATUS is CANCELED, the task has been canceled.

     For more information about the columns in the DBA_OB_LS_REPLICA_TASK_HISTORY view, see DBA_OB_LS_REPLICA_TASK_HISTORY.

References

• Add a replica

• Reduce replicas

• Convert replica types

• Modify the quorum count of a log stream

• Replica migration