Creating a Proxy Instance for Read/Write Splitting

1. Log in to the TaurusDB console.
2. Click in the upper left corner and select a region.
3. On the Instances page, click the instance name.
4. In the navigation pane, choose Database Proxy.
5. Click Create Proxy Instance.
6. On the displayed page, set required parameters and click Next.
   Figure 1 Creating a proxy instance
   
   Figure 2 Setting the read weight
   

   Table 1 Parameter description

   Parameter	Description
   Proxy Instance Name	The name can consist of 4 to 64 characters and must start with a letter. Only letters (case-sensitive), digits, hyphens (-), and underscores (_) are allowed.
   Proxy Mode	You can select Read/Write, Read-only (TP), or Read-only (AP) as needed. Read/Write: All write requests are forwarded only to the primary node, and all read requests are forwarded to the selected nodes based on the read weights or active connections. The default read weight of a node is 100. Read-only (TP): Write requests are not forwarded to any node. All read requests are forwarded to the selected read replicas based on the read weights or active connections. The read requests are not forwarded to the primary node, even if the primary node is selected. Only read requests are supported in the read-only (TP) mode. If write requests are forwarded to any node, an error message is displayed. DDL, DML, and temporary table operations are not supported in the read-only (TP) mode. Read-only (AP): Write requests are not forwarded to any node. All read requests are forwarded to the selected nodes based on the read weights. This mode is in the OBT phase. To use it, submit a service ticket. Only the weighted routing policy is supported in the read-only (AP) mode. The weights of AP nodes cannot be all 0. Binlog pull is not supported. Session consistency is not supported. Only eventual consistency is supported. Transaction splitting is not supported. The feature for assigning requests to row and column store nodes is not supported. Session-level connection pooling is not supported. ALT is not supported. New nodes cannot be automatically associated with a proxy instance.
   Consistency Level	The consistency level can only be configured when the kernel version of your TaurusDB instance is 2.0.28.1 or later. For details about how to check the kernel version, see How Can I Check the Version of a TaurusDB Instance? Value: Eventual consistency After a proxy instance is created, consecutive SELECT requests within the same session are routed to different nodes based on their configured weights. Due to varying replication latencies between the primary node and the read replicas, the SELECT queries may return inconsistent results. As a result, the proxy instance ensures only eventual consistency by default. To offload read requests from the primary node to read replicas, you can select eventual consistency. Session consistency To prevent data inconsistencies across multiple SELECT requests caused by eventual consistency, the database proxy provides session-level consistency. It guarantees that within a session, each SELECT query returns the latest data written by previous operations in the same session. To use session consistency, the kernel version of your proxy instance must be 2.7.4.0 or later. Global consistency Global consistency ensures data consistency in different sessions. It means that once data is written, you can immediately query the updated data. You can select global consistency when there are more read operations than write operations. Global consistency is only available when the TaurusDB instance kernel is 2.0.57.240900 or later and the proxy instance kernel is 2.25.06.000 or later. For more information about consistency levels, see Changing the Consistency Level of a Proxy Instance.
   Routing Policy	Value: Weighted: Read requests are assigned to nodes based on the weights you specify. Load balancing: Read requests are assigned to nodes with fewer active connections. To use load balancing, the kernel version of your proxy instance must be 2.22.07.000 or later. Nearby AZ: A proxy node preferentially routes read requests to the database nodes in the same AZ as the proxy node. To use the Nearby AZ routing policy, ensure that the proxy instance's engine version is 2.23.12.000 or later. For more information about routing policies, see Changing the Routing Policy of a Proxy Instance.
   Proxy Instance Specifications	You can select the proxy instance specifications as needed. Kunpeng general computing-plus: 2 vCPUs | 4 GB, 4 vCPUs | 8 GB, and 8 vCPUs | 16 GB General-enhanced: 2 vCPUs | 4 GB, 4 vCPUs | 8 GB, and 8 vCPUs | 16 GB
   Subnet	This function is in the OBT phase. To use it, submit a service ticket. When creating a proxy instance, you can specify a subnet for the proxy instance. If the subnet where the TaurusDB instance is associated with is a secondary CIDR block, you can only select the same subnet as the TaurusDB instance for the proxy instance.
   IP Addresses	IPv4 addresses can be automatically or manually assigned. Automatically-assigned: When you create a proxy instance, TaurusDB automatically assigns an IPv4 proxy address. Manually-assigned: You can enter an available IPv4 address within the subnet CIDR block as the proxy address of the TaurusDB instance. You can click View In-use IP Addresses to view the IP addresses that have been used.
   Proxy Instance Nodes	You can enter an integer from 2 to 16. The default value is 2. Number of recommended proxy instance nodes = (Number of vCPUs of the primary node + Total number of vCPUs of all read replicas)/(4 x Number of vCPUs of the proxy instance), rounded up.
   AZ Assignment Mode	Select either of the following modes: Auto Assign: randomly assigns proxy nodes to AZs, with a preference for matching the AZ of the TaurusDB node. Manual assign: assigns proxy nodes to the AZs you specify.
   Node AZ	Select the AZs where proxy nodes will be deployed.
   Associate New Nodes	After Associate New Nodes is enabled, new read replicas will be automatically associated with the proxy instance.
   New Node Weight	If Routing Policy is Weighted, you need to configure read weights for the new nodes. The default weight of a node is 100. Nodes with higher weights process more read requests.
   Auto Assign Requests to Column Store or Row Store Nodes	After this function is enabled, a proxy instance distributes requests based on the actual execution cost of a SQL statement to maximize the query performance. For details about the usage and constraints, see Enabling Request Distribution Among Row Store and Column Store Nodes for Complex OLAP Queries.
   Database Nodes	Select nodes to be associated with the proxy instance for processing read requests. The nodes displayed in the list include TaurusDB nodes (the primary node and read replicas) and HTAP nodes (BE nodes and FE nodes). If Routing Policy is Load balancing, you do not need to configure read weights for selected nodes. Read requests are forwarded to nodes with fewer active connections. If Routing Policy is Weighted, you need to configure read weights of the primary node and read replicas. Read requests are forwarded to nodes based on the weights you specify. For example, the read weights assigned to one primary node and two read replicas are 100, 200, and 200, respectively. In the read/write mode, the primary node and two read replicas process read requests in the ratio of 1:2:2. The primary node processes 20% of read requests, and each read replica processes 40% of read requests. Write requests are automatically routed to the primary node. In the read-only mode, the read weight of the primary node does not take effect, and the two read replicas process 50% of read requests, respectively.

7. Confirm the proxy instance configuration.
   • If you need to modify your settings, click Previous.
   • If you do not need to modify your settings, click Submit.

8. View the proxy instance and associated nodes.

   After the proxy instance creation is complete, you can view the created proxy instance on the Database Proxy page.

   Figure 3 Viewing the created proxy instance
   

   Choose Basic Information in the navigation pane. Click in the upper right corner of the page and select View Instance Topology. In the instance topology, you can view the database nodes associated with the proxy instance. You can move the pointer to a node name to view its details.

   Figure 4 Viewing information about nodes associated with a proxy instance
   

Before using a proxy instance to connect to your TaurusDB instance, ensure that the current database account has the permissions to access the proxy address, or the proxy instance cannot connect to your TaurusDB instance.

You can perform the following steps to check and grant an account the permission to access a proxy address.

1. Connect to your TaurusDB instance through DAS (recommended).
   1. On the Instances page, locate the target instance and click Log In in the Operation column.

      Alternatively, on the Instances page, click the instance name. On the displayed Basic Information page, click Log In in the upper right corner. The DAS login page is displayed.

   2. Enter the login username and password and click Test Connection.

   For details about other connection methods, see Connection Methods.

2. Run the following SQL statement to check whether host of your account contains a proxy address.

   To obtain the proxy address, click the target TaurusDB instance. In the navigation pane, choose Database Proxy. In the proxy instance list, view the proxy address.

   SELECT user,host FROM mysql.user;

   

   If the address is %, the host contains all CIDR blocks.

3. If the host does not contain the CIDR block where the proxy instance is associated with, assign the remote access permissions to the host.

   For example, if you want to connect to the TaurusDB instance using 192.168.0 as user root, set Host to 192.168.% on the DAS user management page. For details, see Editing a User.

   Figure 5 Configuring a host IP address
   

You need to ensure that the inbound and outbound rules allow access from the proxy address. The default port number is 3306.

1. Log in to the TaurusDB console.
2. Click in the upper left corner and select a region.
3. On the Instances page, click the instance name to go to the Basic Information page.
4. In the Network Information area, click the security group name in the Security Group field.
5. On the Inbound Rules tab, check whether access through port 3306 is allowed by default.
   Figure 6 Allowing access through port 3306
   

   If there is no such rule, click Fast-Add Rule. In the displayed dialog box, select MySQL (3306), set the inbound rule parameters, and click OK.

   Figure 7 Fast adding port 3306
   

   Table 2 Inbound rule parameter description

   Parameter	Description
   Protocols and Ports	Select MySQL (3306).
   Type	Supported source IP address type. Its value can be: IPv4 IPv6
   Source	Used to match the source of an external request. The source can be: IP address: The source is a fixed IP address. You can enter or paste multiple IP addresses separated by commas (,). Each IP address represents a different security group rule. Single IP address: IP address/mask Example IPv4 address: 192.168.10.10/32 Example IPv6 address: 2002:50::44/128 IP address range in CIDR notation: IP address/mask Example IPv4 address range: 192.168.52.0/24 Example IPv6 address range: 2407:c080:802:469::/64 Any IP addresses 0.0.0.0/0 represents all IPv4 addresses. ::/0 represents all IPv6 addresses. Security group: The source is another security group. You can select a security group in the same region from the drop-down list. If there is instance A in security group A and instance B in security group B, and the inbound rule of security group A allows traffic from security group B, traffic is allowed from instance B to instance A. IP address group: The source is an IP address group. An IP address group is a collection of one or more IP addresses. You can select an available IP address group from the drop-down list. For IP address ranges and IP addresses with the same security requirements, you can use an IP address group to simplify management. If no IP address groups are available, create one by referring to Creating an IP Address Group.
   Action	A security group rule action. The value can be Allow or Deny. If Action is set to Allow, the rule allows the source addresses to access specified ports of the cloud servers within the security group. If Action is set to Deny, the rule blocks the source addresses from accessing specified ports of the cloud servers within the security group. Security group rules are matched first by priority and then by action. Deny rules take precedence over allow rules.
   Priority	Priority of the security group rule. The priority value ranges from 1 to 100. The default value is 1, which has the highest priority. The security group rule with a smaller value has a higher priority.
   Description	Supplementary information about the security group rule. This parameter is optional. The description can contain a maximum of 255 characters and cannot contain angle brackets (<>).

1. View the proxy address and port on the TaurusDB console.

   Click the TaurusDB instance name. In the navigation pane, choose Database Proxy. In the proxy instance list, view the proxy address and port.

   Figure 8 Viewing a proxy address and port
   

2. Log in to an ECS.

   For details, see Elastic Cloud Server User Guide.

3. Run the following command to connect to the TaurusDB instance through the proxy address:

   mysql -h host -P port -u userName -p

   Example:

   mysql -h 192.168.0.61 -P 3306 -u root -p

   Enter the password of the database account if the following information is displayed:

   Enter password:

   Table 3 Parameter description

   Parameter	Description
   host	Proxy address obtained in 1.
   port	Port obtained in 1.
   userName	Username, that is, the TaurusDB database administrator account. The default value is root.

You can run the show last route command to check the routing result after you perform a read operation.

The following uses a read operation as an example to describe how to view the routing result.

1. After connecting to your TaurusDB instance through the proxy address, perform a read operation.

   Example:

   select 1;

   Figure 9 Performing a read operation
   

2. Run the following command to view the routing result of the read operation in 1:

   show last route;

   Figure 10 Viewing a query result
   

   The IP address in the command output is the IP address of the node to which the read operation is routed. Read operations are routed to the primary node or read replicas based on the specified routing policy.

   

   Do not include show last route in service code or multi-statement requests.