Clear residual cluster information

If the original OBServer node where the arbitration service resides is down or disconnected after you replace or remove the arbitration service, the original OBServer node may contain residual cluster information. You must manually clear the residual cluster information by using the ob_admin tool.

Prerequisites

The ob_admin tool is installed on the original OBServer node where the arbitration service resides. When you deploy the arbitration service on an OBServer node, the ob_admin tool is installed in the /home/admin/oceanbase/bin directory on the OBServer node by default. If the ob_admin tool is not installed on the original OBServer node where the arbitration service resides, you must install the ob_admin tool before you clear the residual cluster information. For more information about how to install the ob_admin tool, see ob_admin overview.

Clear residual information

1. Check the arbitration service.

   1. Log on to the sys tenant of the cluster as the root user.

      Note that you must specify the corresponding fields in the following sample code based on your actual database configurations.

      obclient -h10.xx.xx.xx -P2883 -uroot@sys -p***** -A
      

      For more information about how to connect to a database, see Overview (MySQL mode) or Overview (Oracle mode).

   2. Execute the following statement to verify that the arbitration service of the cluster is replaced or removed.

      SELECT * FROM oceanbase.DBA_OB_ARBITRATION_SERVICE;
      

      The query result is as follows:

      +---------------------+---------------------+-------------------------+---------------------+------------------------------+------+
      | CREATE_TIME         | MODIFY_TIME         | ARBITRATION_SERVICE_KEY | ARBITRATION_SERVICE | PREVIOUS_ARBITRATION_SERVICE | TYPE |
      +---------------------+---------------------+-------------------------+---------------------+------------------------------+------+
      | 2023-06-26 19:30:19 | 2023-06-30 09:42:40 | default                 | xx.xx.xx.194:2882   |                              | ADDR |
      +---------------------+---------------------+-------------------------+---------------------+------------------------------+------+
      1 row in set
      

      If the ARBITRATION_SERVICE field is empty or indicates the IP address and port number of another OBServer node, and the PREVIOUS_ARBITRATION_SERVICE field is empty, the arbitration service of the cluster is replaced or removed, and you can clear the residual cluster information. Otherwise, an arbitration member is providing services, and you cannot clear the residual cluster information.

2. Log on to the original OBServer node where the arbitration service resides and clear the residual cluster information on the OBServer node.

   1. Log on to the original OBServer node where the arbitration service resides.

   2. Go to the directory where the ob_admin tool is installed.

      By default, the ob_admin tool is installed in the /home/admin/oceanbase/bin directory.

      cd /home/admin/oceanbase/bin
      

   3. Execute the following statement to clear the residual cluster information.

      ./ob_admin -h$ARB_SERVER_IP -p$ARB_SERVER_PORT force_clear_arb_cluster_info $CLUSTER_ID
      

      The parameters are described as follows:

      • $ARB_SERVER_IP: the IP address of the original OBServer node where the arbitration service resides.

      • $ARB_SERVER_PORT: the RPC port number of the original OBServer node where the arbitration service resides. By default, Port 2882 is used.

      • $CLUSTER_ID: the ID of the cluster. To obtain the cluster ID, connect to the database and execute the SHOW PARAMETERS LIKE 'cluster_id'; statement.

        SHOW PARAMETERS LIKE 'cluster_id';
        

        The query result is as follows:

        +-------+----------+----------------+----------+------------+-----------+----------+-------------------+----------+---------+---------+-------------------+
        | zone  | svr_type | svr_ip         | svr_port | name       | data_type | value    | info              | section  | scope   | source  | edit_level        |
        +-------+----------+----------------+----------+------------+-----------+----------+-------------------+----------+---------+---------+-------------------+
        | zone1 | observer | xx.xx.xx.197   |     2882 | cluster_id | NULL      | 20230625 | ID of the cluster | OBSERVER | CLUSTER | DEFAULT | DYNAMIC_EFFECTIVE |
        | zone2 | observer | xx.xx.xx.194   |     2882 | cluster_id | NULL      | 20230625 | ID of the cluster | OBSERVER | CLUSTER | DEFAULT | DYNAMIC_EFFECTIVE |
        +-------+----------+----------------+----------+------------+-----------+----------+-------------------+----------+---------+---------+-------------------+
        2 rows in set
        

        The query result shows that the cluster_id of the cluster is 20230625.

      The following sample statement clears the residual information of the specified cluster:

      ./ob_admin -hxx.xx.xx.64 -p2882 force_clear_arb_cluster_info 20230625
      

      The execution result is as follows:

      succ to open, filename=ob_admin.log, fd=3, wf_fd=2
      old log_file need close, old = ob_admin.log new = ob_admin.log
      succ to open, filename=ob_admin.log, fd=3, wf_fd=2
      succ to open, filename=ob_admin_rs.log, fd=4, wf_fd=2
      

References

• Replace the arbitration service for a cluster

• Remove the arbitration service for a cluster

• Deploy an OceanBase cluster with two replicas and the arbitration service