Connect to PolarDB for MySQL | endpoint, client, CLI - PolarDB

Connect to a PolarDB for MySQL cluster using DMS, a MySQL client, the command line, or application code.

Prerequisites

Complete the following tasks before you connect:

Obtain the database endpoint and port
Go to the PolarDB console. In the Cluster List, click the ID of the target cluster to go to the cluster details page. In the Database Connection section, obtain the database endpoint (primary endpoint, cluster endpoint, and custom endpoint).
Note
Use the cluster endpoint. The default port is 3306.
Select private network or public network based on your access environment.
If you use an ECS instance to access PolarDB and the ECS instance and the PolarDB cluster are in the same VPC, select private network.
If you access PolarDB from an on-premises environment, select public network. To obtain a public endpoint, click Request on the right.
The public network is the Internet. Accessing the cluster over the public network may not deliver optimal performance for your PolarDB cluster.
Virtual hosts and simple application servers cannot connect to PolarDB through a private network endpoint.
Create a database account
Go to the PolarDB console. In the Cluster List, click the ID of the target cluster to go to the cluster details page. On the Configurations and Management > Account Management page, create a database account.
Note
Database accounts are categorized into privileged accounts and standard accounts with different permissions. Create an account based on your needs.
Configure a cluster whitelist
Go to the PolarDB console. In the Cluster List, click the ID of the target cluster to go to the cluster details page. On the Configurations and Management > Cluster Whitelist page, add an IP whitelist or a security group.
Note
If you use an ECS instance to access PolarDB and the ECS instance and the PolarDB cluster are in the same VPC, you can add the private IP address of the ECS instance to a new IP whitelist group, or add the security group of the ECS instance to the cluster whitelist.
If you use an ECS instance to access PolarDB, but the ECS instance and the PolarDB cluster are not in the same VPC, you can add the public IP address of the ECS instance to a new IP whitelist group, or add the security group of the ECS instance to the cluster whitelist.
If you access PolarDB from an on-premises environment, add the public IP address of your on-premises environment to a new IP whitelist group.
Obtain your public IP address:
Linux operating system: Open the terminal and run the curl ifconfig.me command.
Windows operating system: Open the command prompt and run the curl ip.me command.
macOS operating system: Open the terminal and run the curl ifconfig.me command.
If your on-premises network environment uses a proxy server or has other similar configurations, the IP address obtained using the preceding methods may not be your real public IP address. You can add the IP address range 0.0.0.0/0 to the PolarDB cluster whitelist. After you successfully connect to the cluster, run the SHOW PROCESSLIST; command to obtain the real public IP address and add it to the cluster whitelist. Then, remove the IP address range 0.0.0.0/0 from the whitelist.
The IP address range 0.0.0.0/0 allows access from all sources, which poses a significant security threat. Do not add it to the whitelist unless necessary.

After completing the prerequisites, connect to the cluster.

Connect to a database cluster

Choose a connection method that suits your needs:

Use DMS to connect to the cluster

DMS is a graphical data management service from Alibaba Cloud. You can manage your PolarDB cluster directly in DMS without installing additional tools.

Go to the PolarDB console. In the Cluster List, click the ID of the target cluster to go to the cluster details page. In the upper-right corner of the page, click Log on to Database.
Enter your database account and database password for the PolarDB for MySQL cluster, then click Log on.
After you log on, find the PolarDB for MySQL cluster in the Logged-in Instances list in the left navigation pane.

Use a client to connect to the cluster

You can use any MySQL-compatible client to connect to a PolarDB cluster. The following example uses MySQL Workbench 8.0.29.

Download and install MySQL Workbench.
Open MySQL Workbench and choose Database > Connect to Database.

Enter the connection information and click OK.

Connection dialog

Parameter	Description	Example
Hostname	The database endpoint.	pc-2***.rwlb.rds.aliyuncs.com
Port	The port number of the database endpoint. Note The default port is 3306.	3306
Username	The database account.	polardb_mysql_user
Password	The password of the database account.	Pass***233

Use the command line to connect to the cluster

If a MySQL client is installed on your server, run the following command to connect to the PolarDB for MySQL cluster.

Syntax:

mysql -h<endpoint> -P<port> -u<database_username> -p<database_user_password>

Example:

mysql -h pc-2***.rwlb.rds.aliyuncs.com -P3306 -upolardb_mysql_user -pPass***233

Parameter	Description	Example
-h	The database endpoint.	pc-2***.rwlb.rds.aliyuncs.com
-P	The port number of the database endpoint. Note The default port is 3306. If the port is the default port, you can omit this parameter.	3306
-u	The database account.	polardb_mysql_user
-p	The password of the database account. Note This parameter is required. If you omit this parameter, you are prompted to enter the password after `Enter password`. If you include this parameter, do not add a space between `-p` and the password.	Pass***233

Use an application to connect to the cluster

Connecting to a PolarDB for MySQL cluster is the same as connecting to any MySQL database. Replace the endpoint, port, account, and password with your PolarDB cluster values. Examples by language:

Java

Use the MySQL JDBC driver in a Maven project to connect to a PolarDB for MySQL cluster.

Add the MySQL JDBC driver dependency to your pom.xml file:

<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>8.0.27</version>
</dependency>

Connect to the cluster. Replace <HOST>, <USER>, <PASSWORD>, <DATABASE>, <YOUR_TABLE_NAME>, and <YOUR_TABLE_COLUMN_NAME> with your actual values.

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;

public class DatabaseConnection {
   public DatabaseConnection() {
   }

   public static void main(String[] args) {
      // The endpoint, port, and name of the database to connect to.
      String url = "jdbc:mysql://<HOST>:3306/<DATABASE>?useSSL=false&serverTimezone=UTC";
      // The database account.
      String user = "<USER>";
      // The password of the database account.
      String password = "<PASSWORD>";

      try {
         Class.forName("com.mysql.cj.jdbc.Driver");
         Connection conn = DriverManager.getConnection(url, user, password);
         Statement stmt = conn.createStatement();
         // The name of the data table to retrieve.
         ResultSet rs = stmt.executeQuery("SELECT * FROM `<YOUR_TABLE_NAME>`");

         while(rs.next()) {
            // The name of the column in the data table to retrieve.
            System.out.println(rs.getString("<YOUR_TABLE_COLUMN_NAME>"));
         }

         rs.close();
         stmt.close();
         conn.close();
      } catch (Exception var7) {
         var7.printStackTrace();
      }

   }
}

Python

Use the PyMySQL library with Python 3 to connect to a PolarDB for MySQL cluster.

Install the PyMySQL library:
```
pip3 install PyMySQL
```

Connect to the cluster. Replace <HOST>, <USER>, <PASSWORD>, <DATABASE>, and <YOUR_TABLE_NAME> with your actual values.

import pymysql

# Database connection parameters
host = '<HOST>'  # The endpoint of the PolarDB cluster
port = 3306  # The default port is 3306
user = '<USER>'  # The database account
password = '<PASSWORD>'  # The password of the database account
database = '<DATABASE>'  # The name of the database to connect to

try:
    # Create a database connection
    connection = pymysql.connect(
        host=host,
        port=port,
        user=user,
        passwd=password,
        db=database
    )

    # Get the cursor
    with connection.cursor() as cursor:
        # Execute an SQL query
        sql = "SELECT * FROM `<YOUR_TABLE_NAME>`"  # The name of the data table to retrieve
        cursor.execute(sql)

        # Get the query results
        results = cursor.fetchall()
        for row in results:
            print(row)

finally:
    # Close the database connection
    if 'connection' in locals() and connection.open:
        connection.close()

Go

Use the database/sql package and go-sql-driver/mysql driver (Go 1.23.0) to connect to a PolarDB for MySQL cluster.

Install the go-sql-driver/mysql driver:

go get -u github.com/go-sql-driver/mysql

Connect to the cluster. Replace <HOST>, <USER>, <PASSWORD>, <DATABASE>, and <YOUR_TABLE_NAME> with your actual values.

package main

import (
    "database/sql"
    "fmt"
    "log"
    _ "github.com/go-sql-driver/mysql"
)

func main() {
    // Database connection parameters
    dbHost := "<HOST>"       // The endpoint of the PolarDB cluster
    dbPort := "3306"         // The default port is 3306
    dbUser := "<USER>"       // The database account
    dbPass := "<PASSWORD>"   // The password of the database account
    dbName := "<DATABASE>"   // The name of the database to connect to

    // Build the Data Source Name (DSN)
    dsn := fmt.Sprintf("%s:%s@tcp(%s:%s)/%s?charset=utf8mb4&parseTime=True&loc=Local", dbUser, dbPass, dbHost, dbPort, dbName)

    // Open a database connection
    db, err := sql.Open("mysql", dsn)
    if err != nil {
        log.Fatalf("Failed to connect to database: %v", err)
    }
    defer db.Close()

    // Test the connection
    err = db.Ping()
    if err != nil {
        log.Fatalf("Failed to ping database: %v", err)
    }

    // Create a cursor
    var result string
    err = db.QueryRow("SELECT VERSION()").Scan(&result)
    if err != nil {
        log.Fatalf("Failed to execute query: %v", err)
    }

    // Print the database version
    fmt.Printf("Connected to database, version: %s\n", result)

    // Execute an SQL query
    rows, err := db.Query("SELECT * FROM `<YOUR_TABLE_NAME>`") // The name of the data table to retrieve
    if err != nil {
        log.Fatalf("Failed to execute query: %v", err)
    }
    defer rows.Close()
}

FAQ

An ECS instance cannot connect to a PolarDB cluster

Troubleshoot as follows:

Check whether the PolarDB cluster is in the running state.
Verify that the database endpoint, port, account, and password are correct. Obtain the database endpoint and port.
Test network connectivity from the ECS instance using ping <database endpoint> or telnet <database endpoint> <port>.
1. If you are using a private network endpoint:
  1. Check whether the ECS instance and the PolarDB cluster are in the same VPC. If they are not in the same VPC, you cannot use the private network endpoint. Use one of the following solutions to place the ECS instance and the PolarDB cluster in the same VPC:
    - Switch the VPC of the ECS instance.
    - If your cluster is a Cluster Edition cluster, you can switch the VPC of the cluster.
    - Use Cloud Enterprise Network (CEN) to enable communication between VPCs in the same region.
  2. Check whether the private IP address, IP address range, or security group of the ECS instance is added to the cluster whitelist.
2. If you are using a public network endpoint, check whether the public IP address or security group of the ECS instance is added to the cluster whitelist.

Note

Virtual hosts and simple application servers cannot connect to PolarDB through a private network endpoint.

An on-premises environment cannot connect to a PolarDB cluster

Troubleshoot as follows:

Check whether the PolarDB cluster is in the running state.
Verify that the database endpoint, port, account, and password are correct. Obtain the database endpoint and port.
Note
The database endpoint must be a public network endpoint. If you are using an ECS instance that is in the same VPC as the PolarDB cluster, you can use a private network endpoint.
Test network connectivity from your on-premises environment using ping <database endpoint> or telnet <database endpoint> <port>.
Check whether the public IP address or IP address range of your on-premises environment is added to the cluster whitelist.
Obtain your public IP address:
- Linux operating system: Open the terminal and run the curl ifconfig.me command.
- Windows operating system: Open the command prompt and run the curl ip.me command.
- macOS operating system: Open the terminal and run the curl ifconfig.me command.
If your on-premises network environment uses a proxy server or has other similar configurations, the IP address obtained using the preceding methods may not be your real public IP address. You can add the IP address range 0.0.0.0/0 to the PolarDB cluster whitelist. After you successfully connect to the cluster, run the SHOW PROCESSLIST; command to obtain the real public IP address and add it to the cluster whitelist. Then, remove the IP address range 0.0.0.0/0 from the whitelist.

Cannot connect to a PolarDB cluster with the error "Access denied for user 'xxx'@'xxx' (using password: YES)"

The database account or password is incorrect. Go to the PolarDB console and verify or reset credentials on the Configurations and Management > Account Management page.

Cannot connect to a PolarDB cluster with the error "Unknown MySQL server host 'xxx'"

The database endpoint is incorrect. The correct format is pc-xxxxxx.rwlb.rds.aliyuncs.com. Go to the PolarDB console and verify the endpoint in the Basic Information > Database Connection section.

Cannot connect to a PolarDB cluster with the error "Can't connect to MySQL server on 'xxx'" or "Connection timed out"

The public IP address or IP address range of your environment is likely not in the PolarDB cluster whitelist, or the IP address you entered is incorrect.

Obtain your public IP address:

Linux operating system: Open the terminal and run the curl ifconfig.me command.
Windows operating system: Open the command prompt and run the curl ip.me command.
macOS operating system: Open the terminal and run the curl ifconfig.me command.

If your on-premises network environment uses a proxy server or has other similar configurations, the IP address obtained using the preceding methods may not be your real public IP address. You can add the IP address range 0.0.0.0/0 to the PolarDB cluster whitelist. After you successfully connect to the cluster, run the SHOW PROCESSLIST; command to obtain the real public IP address and add it to the cluster whitelist. Then, remove the IP address range 0.0.0.0/0 from the whitelist.

How do I change the connection method in DMS to use a cluster endpoint to connect to a PolarDB cluster?

When you use DMS to connect to a cluster, DMS connects through the Primary Endpoint by default. To use features such as In-Memory Column Index (IMCI) and PolarDB for AI, switch to the Cluster Endpoint so that the PolarDB database proxy routes SQL statements to the corresponding functional nodes.

Procedure:

After connecting to the cluster through DMS, in the Database Instances > Logged-in Instances list in the navigation pane on the left, find the target cluster, right-click it, and select Edit Instance.
In the Edit Instance dialog box, change Basic Information > Entry Method to Connection String, enter the cluster endpoint of the cluster, and click Save.

Important

After changing the endpoint, close the existing SQL window and open a new one. The original window still uses the Primary Endpoint, not the updated Connection String Address.

Why do connection errors occur after I set the weight of a read-only node in a cluster endpoint to 0 and then remove the node?

Scenario: You need to remove a read-only node from a cluster endpoint. To avoid affecting connections to the node, you first set the read/write splitting weight of the read-only node to 0. You expect that after the weight is set to 0, subsequent read requests will not be sent to this read-only node. However, after you remove the node from the cluster endpoint, connection errors occur on the application side.
Cause: A cluster endpoint has two Load Balancing Policy: Active Request-based Load Balancing and Connections-based Load Balancing:
- Active Request-based Load Balancing: After reducing the weight of a read-only node to 0, subsequent requests will no longer be routed to that node.
- Connections-based Load Balancing: Load balancing is performed only during the connection establishment phase. If a previously established connection is connected to a read-only node, subsequent requests on that connection are always sent to that read-only node.
Solution:
1. Switch the Load Balancing Policy for the cluster endpoint to Active Request-based Load Balancing.
2. Set the read/write splitting weight of the target read-only node to 0.
3. Remove the read-only node.

PolarDB:Connect to a database