Modify the log stream downgrade control time

When you enable the arbitration service for a tenant, you must specify the log stream downgrade control time. When log synchronization fails due to failures of half of the full-featured replicas and the log stream downgrade control time is reached, the arbitration service automatically performs the log stream downgrade process to recover services. The default log stream downgrade control time is 5s, which indicates the service interruption duration when an IDC fails.

Procedure

1. Log on to the database as an administrator of the sys tenant or a user tenant.

   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. Query the log stream downgrade control time of the arbitration service for a tenant.

   • Execute the following statement in the sys tenant to query the log stream downgrade control time for the specified tenant:

     SHOW PARAMETERS LIKE 'arbitration_timeout' TENANT = 'tenant_name';
     

     Here is an example:

     SHOW PARAMETERS LIKE 'arbitration_timeout' TENANT = 'mysql';
     

   • Execute the following statement in a user tenant to query the log stream downgrade control time for the user tenant:

     SHOW PARAMETERS LIKE 'arbitration_timeout';
     

   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 | arbitration_timeout | NULL      | 5s    | The timeout before automatically degrading when arbitration member exists. Range: [3s,+∞]   | TRANS   | TENANT | DEFAULT | DYNAMIC_EFFECTIVE |
   | zone2 | observer | xx.xx.xx.194   |     2882 | arbitration_timeout | NULL      | 5s    | The timeout before automatically degrading when arbitration member exists. Range: [3s,+∞]   | TRANS   | TENANT | DEFAULT | DYNAMIC_EFFECTIVE |
   +-------+----------+----------------+----------+---------------------+-----------+-------+---------------------------------------------------------------------------------------------+---------+--------+---------+-------------------+
   2 rows in set
   

3. Select an appropriate statement to modify the log stream downgrade control time based on your business scenario.

   The arbitration_timeout parameter specifies the control time for triggering automatic downgrade of a log stream for a tenant. The default value is 5s. The value range is [3s,+∞). If you want to avoid the downgrade and achieve the effect that is similar to the Maximum Protection mode for standby clusters in primary/standby deployment in OceanBase Database V3.x, you can specify a larger value, such as 30d, which indicates that the downgrade timeout period is 30 days. The modification of this parameter takes effect immediately without restarting the OBServer node.

   • Execute the following statement in a user tenant to modify the log stream downgrade control time for the user tenant:

     ALTER SYSTEM SET arbitration_timeout = '10s';
     

   • Execute the following statement in the sys tenant to modify the log stream downgrade control time for the specified tenant:

     ALTER SYSTEM SET arbitration_timeout = '10s' TENANT = 'tenant_name';
     

   • Execute the following statement in the sys tenant to modify the log stream downgrade control time for all tenants:

     ALTER SYSTEM SET arbitration_timeout = '10s' TENANT = all;
     

References

For more information about the arbitration service, see the following topics:

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

• Overview

• Enable the arbitration service for a tenant

• Disable the arbitration service for a tenant

• Replace the arbitration service for a cluster

• Remove the arbitration service for a cluster