Add a node

You can add a node to an OceanBase cluster for elastic scaling or deployment adjustment.

• Elastic scaling: After a scale-out, more nodes are available in a zone to accommodate resource units. Then, you can perform a series of operations, such as migrating a unit, modifying the UNIT_NUM parameter for a tenant, and creating a tenant.

• Deployment adjustment: You can adjust the deployment mode of a cluster from three IDCs in the same region to five IDCs across three regions, and migrate a zone from one IDC to another when an IDC is to be demolished. In this scenario, you must first add a zone, add nodes to the zone, and then modify the locality of the tenant.

OceanBase Database outperforms conventional databases in scaling due to its distributed architecture. A conventional database stores its data on a single server, but OceanBase Database scatters its data on different servers, enhancing scalability. When the capacity of a cluster instance or tenant is insufficient, you only need to add more nodes. In this way, the cluster instance can accommodate more tenants and each tenant can accommodate more data and business traffic. When the capacity of a cluster or tenant is in surplus, you can remove nodes to reduce the cost.

The multi-replica deployment capability of OceanBase Database contributes to its architectural benefits against conventional databases. The multi-replica deployment capability is the basis for OceanBase Database to achieve lossless disaster recovery in different levels, including the server level, IDC level, and city level. OceanBase Database allows you to flexibly adjust the cluster deployment architecture to adapt to the technical evolution of business systems.

Prerequisites

• All OBServer hosts to be added have been configured. For more information, see Before deployment.

• OceanBase Database is installed on all OBServer hosts to be added. You can download the installation package from the Download Center or request the installation package from OceanBase Technical Support.

Procedure

1. (Optional) In the case where you must first add a zone before you can add nodes to the zone, make sure that the zone has been added. For information about how to add a zone, see Add a zone.

2. Use SSH to log in to an OBServer host to be added, initialize the OBServer host, and configure the clock source.

   For information about how to initialize an OBServer host, see Initialize an OBServer node by using oatcli.

   For information about how to configure the clock source, see Configure the clock source.

3. Install the RPM package of OceanBase Database.

   Before you add OBServer nodes, you must install the OceanBase Database software on the OBServer hosts.

   The syntax of the command is as follows:

   [root@xxx /]#cd $rpm_dir
   
   [root@xxx $rpm_dir]#rpm -ivh $rpm_name
   

   Here, $rpm_dir specifies the directory in which the RPM package is stored, and $rpm_name specifies the name of the RPM package.

4. Initialize the directories of OceanBase Database.

   We recommend that you set the data directory of OceanBase Database on an independent disk and link this directory to the home directory of OceanBase Database by using a soft link.

   [root@xxx admin]#su - admin
   -bash-4.2$ mkdir -p /data/1/$cluster_name/{etc3,sort_dir,sstable,slog} 
   -bash-4.2$ mkdir -p /data/log1/$cluster_name/{clog,etc2,ilog,oob_clog} 
   -bash-4.2$ mkdir -p /home/admin/oceanbase/store/$cluster_name
   -bash-4.2$ for t in {etc3,sort_dir,sstable,slog};do ln -s /data/1/$cluster_name/$t /home/admin/oceanbase/store/$cluster_name/$t; done
   -bash-4.2$ for t in {clog,etc2,ilog,oob_clog};do ln -s /data/log1/$cluster_name/$t /home/admin/oceanbase/store/$cluster_name/$t; done
   

   Here, cluster_name specifies the name of the cluster to which the OBServer host is to be added.

   Here is an example:

   [root@xxx admin]#su - admin
   -bash-4.2$ mkdir -p /data/1/obdemo/{etc3,sort_dir,sstable,slog} 
   -bash-4.2$ mkdir -p /data/log1/obdemo/{clog,etc2,ilog,oob_clog} 
   -bash-4.2$ mkdir -p /home/admin/oceanbase/store/obdemo
   -bash-4.2$ for t in {etc3,sort_dir,sstable,slog};do ln -s /data/1/obdemo/$t /home/admin/oceanbase/store/obdemo/$t; done
   -bash-4.2$ for t in {clog,etc2,ilog,oob_clog};do ln -s /data/log1/obdemo/$t /home/admin/oceanbase/store/obdemo/$t; done
   

5. Start the observer process on the nodes.

   Run the following command to start the observer process:

   [root@xxx admin]$ su - admin
   
   -bash-4.2$ /home/admin/oceanbase/bin/observer -I xx.xx.xx.xx -P XXXX -p YYYY -z zone1 -d /home/admin/oceanbase/store/obdemo -r 'xx.xx.xx.xx:xxxx:yyyy' -c 20190716 -n obdemo -o "system_memory=30GB,datafile_size=100G,config_additional_dir=/data/1/obdemo/etc3;/data/log1/obdemo/etc2"
   

   where:

   • -I specifies the IP address of the node to be started. In multi-node deployment, you cannot use 127.0.0.1 as the target IP address.

     In the current OceanBase Database version, you can still specify the NIC name to start a node, such as -i eth0. However, we recommend that you specify the IP address to start a node, such as -I 10.10.10.1. You can also specify both the IP address and the NIC name to start a node, such as -I 10.10.10.1 -i eth0. However, this is not recommended.

     In the current version, you can specify an IPv6 address for a node. If you do so, observe the following notes:

     • IPv6 addresses are classified into global addresses and link addresses. We recommend that you use a global address.

     • You need to add -6 prior to the -I parameter.

     Notice

     When you specify the IP address to start the observer process in the current version, if no local NIC whose name matches the IP address specified by local_ip is found, the startup will not fail. The system records an error log and uses the device name specified by devname as the local NIC name.

   • -c specifies the cluster ID. You can execute the SHOW PARAMETERS LIKE 'cluster_id'; statement to obtain the cluster ID.

   • -p specifies the SQL port number, which is generally 2881. We recommend that you do not modify the SQL port number unless necessary.

   • -P specifies the RPC port number, which is generally 2882. We recommend that you do not modify the SQL port number unless necessary.

   • -n specifies the name of the cluster. You can execute the SHOW PARAMETERS LIKE 'cluster'; statement to obtain the cluster name. In this example, the cluster name is obdemo.

   • -z specifies the zone to which the OBServer node is to be added. You can query the DBA_OB_ZONES view for the names of zones in a cluster.

   • -d specifies the data directory.

   • -r specifies the RootService address list of the OceanBase cluster to which the OBServer node is to be added.

     If you specify IPv6 addresses, observe the following notes:

     • IPv6 addresses are classified into global addresses and link addresses. We recommend that you use a global address.

     • An IP address must be enclosed with square brackets ([ ]).

     • You need to add -6 prior to the -r parameter.

   • -l specifies the level of logs to be printed. The value is WARN in this example, indicating that logs of the WARNING level are to be printed.

     For more information about the log levels in OceanBase Database, see Log levels.

   • -o specifies the startup parameters of the cluster, which must be configured based on the actual situation.

     When the -o option is used, note that:

     • The parameters are case-insensitive. However, we recommend that you set them based on the names in observer.config.bin.

     • A parameter name cannot contain the following special characters: spaces, \r, \n, and \t.

     • An equal sign (=) is required between the name and the value of a parameter.

     • Separate the parameters with commas (,).

     Parameters in the -o option are described as follows:

     • system_memory: the size of the internal reserved memory of OceanBase Database, which is 30 GB by default.
     • datafile_size: the size of SSTable files (initialized at a time) in OceanBase Database. This value is estimated based on the available space of /data/1/. We recommend that you specify the value to at least 100 GB and keep some reserved space.
     • config_additional_dir: the redundancy directory for parameter files.

   Here is an example:

   [root@xxx admin]$ su - admin
   
   -bash-4.2$ /home/admin/oceanbase/bin/observer -I xx.xx.xx.1 -c 20221216 -p 2881 -P 2882 -z zone4 -n obdemo -d /home/admin/oceanbase/store/obdemo -r 'xx.xx.xx.1:2882:2881' -l WARN -o "system_memory=30GB,datafile_size=100G,config_additional_dir=/data/1/obdemo/etc3;/data/log1/obdemo/etc2"
   

   Here is an example of starting the observer process on a node with an IPv6 address:

   [root@xxx admin]$ su - admin
   
   -bash-4.2$ /home/admin/oceanbase/bin/observer -6 -I xxxx:xxxx:xxxx:xxxx:xxx:xxxx:xxxx:ebd8 -c 20221216 -p 2881 -P 2882 -z zone4 -n obdemo -d /home/admin/oceanbase/store/obdemo -r '[xxxx:xxxx:xxxx:xxxx:xxx:xxxx:xxxx:ebd8]:2882:2881' -l WARN -o "system_memory=30GB,datafile_size=100G,config_additional_dir=/data/1/obdemo/etc3;/data/log1/obdemo/etc2"
   

6. (Optional) To add more OBServer nodes, repeat steps 2 to 5.

7. Add the node to the cluster.

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

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

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

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

   2. Execute the following statement to add the node to a zone of the cluster:

      ALTER SYSTEM ADD SERVER 'svr_ip:svr_port' [,'svr_ip:svr_port'...] [ZONE [=] 'zone_name'];
      

      where:

      • svr_ip specifies the IP address of the node to be added.

      • svr_port specifies the RPC port of the node to be added. The default value is 2882.

      • zone_name specifies the name of the zone to which the node is to be added.

      Here is an example:

      ALTER SYSTEM ADD SERVER '10.xx.xx.xx:2882','10.xx.xx.xx:2882' ZONE 'zone4';
      

      This statement adds the OBServer node to the service list. Only OBServer nodes in the service list can provide services.

8. After the statement is executed, you can query the DBA_OB_SERVERS view to verify whether the node is added.

   Here is an example:

   SELECT * FROM oceanbase.DBA_OB_SERVERS;
   

   If the OBServer node appears in the list, it is successfully added.

What to do next

You can add nodes for elastic scaling or deployment adjustment.

• Elastic scaling: After a node is added, more nodes are available in the zone to accommodate resource units. Then, you can perform a series of operations, such as migrating a unit, modifying the UNIT_NUM parameter for a tenant, and creating a tenant. For more information, see the following topics:

  • Migrate units

  • Modify the number of resource units for a tenant

  • Create a tenant

• Deployment adjustment: You can adjust the deployment mode of a cluster from three IDCs in the same region to five IDCs across three regions, and migrate a zone from one IDC to another when an IDC is to be demolished. In this scenario, you must first add a zone, add nodes to the zone, and then modify the locality of the tenant. For more information about how to modify the locality of a tenant, see Modify locality.

References

For more information about node-related O&M operations, see the following topics:

• View a node

• Restart a node

• Delete a node

• Isolate a node

• Replace a node