PolarProxy

Architecture

A PolarDB cluster of Cluster Edition consists of a primary node and multiple read-only nodes. By default, a PolarDB cluster provides two types of endpoints: a primary endpoint and cluster endpoints. Cluster endpoints are provided by PolarProxy. You can use the cluster endpoints in read/write (automatic read/write splitting) mode or read-only mode.

PolarProxy Enterprise Editions

Billing

Limits

Only clusters of PolarDB Cluster Edition support cluster endpoints and PolarProxy.

Usage notes

• PolarProxy does not support compression protocols for the default and custom cluster endpoints.

• If you do not enable the transaction splitting feature after cluster endpoints are used, all the requests in a transaction are forwarded to the primary node.

• When you execute the SHOW PROCESSLIST statement after you connect to a cluster by using a cluster endpoint, the system returns the results of all nodes.

• If you execute multi-statement or call stored procedures, all subsequent requests for the current connection are forwarded to the primary node. To use the read/write splitting feature, you must close the current connection and reconnect to the cluster.

• No limit is imposed on the maximum number of connections to a PolarDB cluster endpoint. The maximum number of connections varies based on the specifications of the compute nodes in the cluster. If an application connects to a cluster by using a cluster endpoint that supports read/write splitting, the application establishes a connection to each compute node in the cluster. In this case, the maximum number of connections that an application can use is the maximum number of connections of a single compute node. If an application connects to the cluster by using a cluster endpoint in read-only mode, the application establishes a connection to only one compute node in the cluster. In this case, the maximum number of connections that the application can use is the sum of the maximum numbers of connections of all read-only nodes associated with the cluster endpoint. For an application that connects to the cluster by using a cluster endpoint in read/write splitting mode, you can use the transaction-level connection pool feature to increase the maximum number of connections that the application can use. For more information, see the "Transaction-level connection pools" section of the Connection pools topic.

• If a session that supports read/write splitting is created after you add or restart a read-only node, read requests are forwarded to the read-only node. If a session that supports read/write splitting is created before you add or restart a read-only node, read requests are not forwarded to the read-only node. To forward these read requests to the read-only node, you must close the connection and reconnect to the cluster. For example, you can restart your application to establish a new connection.

• Do not modify environment variables when you call stored procedures or execute multiple statements, such as SET NAMES utf8mb4;SELECT * FROM t1;. Otherwise, the data read from the primary node and read-only nodes is inconsistent.

• To prevent the application connection pool from being hung due to packet loss caused by network issues or other unexpected scenarios when you use the application connection pool feature to access a URL, we recommend that you add the connectTimeout and socketTimeout parameters to the URL. For more information about the parameters, see Parameters. Example:

  java url: jdbc:mysql://ip:port/db?connectTimeout=60000&socketTimeout=300000;

Upgrade the specifications of PolarProxy

The default specifications of PolarProxy Enterprise Edition are sufficient for most application scenarios. When you perform stress tests or the service throughput is high, the specifications of PolarProxy Enterprise Edition are automatically upgraded in real time based on the workloads of PolarProxy to meet your business requirements. You can also manually upgrade the specifications pf PolarProxy of previous versions.

For more information about how to upgrade the specifications of PolarProxy, see Upgrade the specifications of PolarProxy.

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