Set the log synchronization bandwidth limit

Bandwidth between the primary and standby tenants can be a scarce resource in certain business scenarios, such as cross-region disaster recovery scenarios. It is necessary to use this resource efficiently and apply appropriate bandwidth limitations.

OceanBase Database provides the following two cluster-level parameters for bandwidth limitation on standby tenants:

• standby_fetch_log_bandwidth_limit: Used to set the total bandwidth available for log synchronization from the primary or source tenant to the standby tenant, in the cluster where the standby tenant is located. The value range of this parameter is [0, 10000G]. The default value is 0, which means no bandwidth limit. Any modifications to this parameter take effect immediately.

  After the standby_fetch_log_bandwidth_limit parameter is modified, OceanBase Database uses an adaptive allocation policy to distribute suitable upper limit values for available bandwidth among multiple OBServer nodes in the cluster. This ensures maximum utilization of the available bandwidth resources.

• _server_standby_fetch_log_bandwidth_limit: Used to set the bandwidth available for log synchronization from the primary or source tenant to the standby tenant, for a single OBServer node in the cluster where the standby tenant is located. The value range of this parameter is [0, 1000G]. The default value is 0, which means no server-level bandwidth limit. Instead, it uses the bandwidth allocated based on the standby_fetch_log_ratelimit parameter. Any modifications to the _server_standby_fetch_log_bandwidth_limit parameter take effect immediately.

  After the _server_standby_fetch_log_bandwidth_limit parameter is modified, the OBServer nodes that have been limited will use this bandwidth limit value, and the bandwidth limit value specified by standby_fetch_log_bandwidth_limit will be allocated to the remaining OBServer nodes. In other words, if both standby_fetch_log_bandwidth_limit and _server_standby_fetch_log_bandwidth_limit are set, the total bandwidth available for the cluster is the sum of the two.

Considerations

• It is not recommended to set the bandwidth limit for a standby tenant too small. In a production environment, it is necessary to evaluate the potential impact of setting bandwidth limit on your business, such as continuous lagging or log interruption of the standby tenant.

• In OceanBase Database, parameters starting with an underscore (_) are called hidden parameters, which are only intended for use by developers during troubleshooting or emergency maintenance.

Procedure

1. Log in to the sys tenant of the cluster where the standby tenant is located, using the root user.

2. Set the 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;
     

     Here is an 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';
     

     where

     • svr_ip: indicates the IP address of the target OBServer node.
     • svr_port: indicates the RPC port number of the target OBServer node.
     • Only one OBServer node can be specified.

     Here is an example:

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

References

• View cluster parameters

• Modify cluster parameters