Specify log synchronization throttling

Bandwidth between a primary tenant and a standby tenant is limited in some business scenarios such as cross-region disaster recovery. You must use the bandwidth properly and enable throttling as needed.

OceanBase Database provides two cluster-level parameters for you to control throttling for a standby tenant.

• standby_fetch_log_bandwidth_limit: the total bandwidth available for the standby tenant to synchronize logs from the primary or source tenant in the cluster where the standby tenant resides. The value range of this parameter is [0,10000G]. The default value is 0, which specifies not to limit the bandwidth. This parameter takes effect immediately after it is modified.

  After you modify the standby_fetch_log_bandwidth_limit parameter, OceanBase Database follows a set of adaptive allocation policies to allocate the maximum bandwidth available for a single OBServer node among multiple OBServer nodes in the cluster. This maximizes the utilization of the bandwidth.

• _server_standby_fetch_log_bandwidth_limit: the bandwidth available for the standby tenant to synchronize logs from the primary or source tenant on a single OBServer node in the cluster where the standby tenant resides. The value range of this parameter is [0,1000G]. The default value is 0, which specifies to use the bandwidth allocated based on the standby_fetch_log_ratelimit parameter without server-level throttling. This parameter takes effect immediately after it is modified.

  After you modify the _server_standby_fetch_log_bandwidth_limit parameter, the throttled OBServer node uses the specified bandwidth limit, and the bandwidth limit is also allocated to other OBServer nodes. In other words, if you specify both the standby_fetch_log_bandwidth_limit and _server_standby_fetch_log_bandwidth_limit parameters, the total bandwidth available for the cluster is the sum of the values of the parameters.

Considerations

• We recommend that you do not set the bandwidth limit for a standby tenant to be excessively small. In the production environment, you must assess possible impact of throttling on your business. For example, throttling for a standby tenant can cause lagging or log interruption of the standby tenant.

• In OceanBase Database, the name of a hidden parameter begins with an underscore (_). Hidden parameters are used by developers only for troubleshooting or emergency O&M.

Procedure

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

2. Specify a bandwidth limit for the standby tenant.

   • Execute the following statement to specify the total bandwidth available for the cluster

     ALTER SYSTEM [SET] standby_fetch_log_bandwidth_limit = value;
     

     For example:

     ALTER SYSTEM SET standby_fetch_log_bandwidth_limit = '50M';
     

   • Execute the following statement to specify the bandwidth available for a single OBServer node

     ALTER SYSTEM [SET] _server_standby_fetch_log_bandwidth_limit = value SERVER [=] 'svr_ip:svr_port';
     

     The parameters are described as follows:

     • svr_ip: the IP address of the OBServer node.
     • svr_port: the RPC port number of the OBServer node.
     • You can specify only one OBServer node.

     For example:

     ALTER SYSTEM SET _server_standby_fetch_log_bandwidth_limit = '30M' SERVER = 'xx.xx.xx.xx:17854';
     

References

• View cluster parameters

• Modify cluster parameters