Connect from Cloud Run

import os

import sqlalchemy


def connect_unix_socket() -> sqlalchemy.engine.base.Engine:
    """Initializes a Unix socket connection pool for a Cloud SQL instance of MySQL."""
    # Note: Saving credentials in environment variables is convenient, but not
    # secure - consider a more secure solution such as
    # Cloud Secret Manager (https://cloud.google.com/secret-manager) to help
    # keep secrets safe.
    db_user = os.environ["DB_USER"]  # e.g. 'my-database-user'
    db_pass = os.environ["DB_PASS"]  # e.g. 'my-database-password'
    db_name = os.environ["DB_NAME"]  # e.g. 'my-database'
    unix_socket_path = os.environ[
        "INSTANCE_UNIX_SOCKET"
    ]  # e.g. '/cloudsql/project:region:instance'

    pool = sqlalchemy.create_engine(
        # Equivalent URL:
        # mysql+pymysql://<db_user>:<db_pass>@/<db_name>?unix_socket=<socket_path>/<cloud_sql_instance_name>
        sqlalchemy.engine.url.URL.create(
            drivername="mysql+pymysql",
            username=db_user,
            password=db_pass,
            database=db_name,
            query={"unix_socket": unix_socket_path},
        ),
        # ...
    )
    return pool

import com.zaxxer.hikari.HikariConfig;
import com.zaxxer.hikari.HikariDataSource;
import javax.sql.DataSource;

public class ConnectorConnectionPoolFactory extends ConnectionPoolFactory {

  // Note: Saving credentials in environment variables is convenient, but not
  // secure - consider a more secure solution such as
  // Cloud Secret Manager (https://cloud.google.com/secret-manager) to help
  // keep secrets safe.
  private static final String INSTANCE_CONNECTION_NAME =
      System.getenv("INSTANCE_CONNECTION_NAME");
  private static final String INSTANCE_UNIX_SOCKET = System.getenv("INSTANCE_UNIX_SOCKET");
  private static final String DB_USER = System.getenv("DB_USER");
  private static final String DB_PASS = System.getenv("DB_PASS");
  private static final String DB_NAME = System.getenv("DB_NAME");

  public static DataSource createConnectionPool() {
    // The configuration object specifies behaviors for the connection pool.
    HikariConfig config = new HikariConfig();

    // The following URL is equivalent to setting the config options below:
    // jdbc:mysql:///<DB_NAME>?cloudSqlInstance=<INSTANCE_CONNECTION_NAME>&
    // socketFactory=com.google.cloud.sql.mysql.SocketFactory&user=<DB_USER>&password=<DB_PASS>
    // See the link below for more info on building a JDBC URL for the Cloud SQL JDBC Socket Factory
    // https://github.com/GoogleCloudPlatform/cloud-sql-jdbc-socket-factory#creating-the-jdbc-url

    // Configure which instance and what database user to connect with.
    config.setJdbcUrl(String.format("jdbc:mysql:///%s", DB_NAME));
    config.setUsername(DB_USER); // e.g. "root", "mysql"
    config.setPassword(DB_PASS); // e.g. "my-password"

    config.addDataSourceProperty("socketFactory", "com.google.cloud.sql.mysql.SocketFactory");
    config.addDataSourceProperty("cloudSqlInstance", INSTANCE_CONNECTION_NAME);

    // Unix sockets are not natively supported in Java, so it is necessary to use the Cloud SQL
    // Java Connector to connect. When setting INSTANCE_UNIX_SOCKET, the connector will 
    // call an external package that will enable Unix socket connections.
    // Note: For Java users, the Cloud SQL Java Connector can provide authenticated connections
    // which is usually preferable to using the Cloud SQL Proxy with Unix sockets.
    // See https://github.com/GoogleCloudPlatform/cloud-sql-jdbc-socket-factory for details.
    if (INSTANCE_UNIX_SOCKET != null) {
      config.addDataSourceProperty("unixSocketPath", INSTANCE_UNIX_SOCKET);
    }


    // ... Specify additional connection properties here.
    // ...

    // Initialize the connection pool using the configuration object.
    return new HikariDataSource(config);
  }
}

const mysql = require('promise-mysql');

// createUnixSocketPool initializes a Unix socket connection pool for
// a Cloud SQL instance of MySQL.
const createUnixSocketPool = async config => {
  // Note: Saving credentials in environment variables is convenient, but not
  // secure - consider a more secure solution such as
  // Cloud Secret Manager (https://cloud.google.com/secret-manager) to help
  // keep secrets safe.
  return mysql.createPool({
    user: process.env.DB_USER, // e.g. 'my-db-user'
    password: process.env.DB_PASS, // e.g. 'my-db-password'
    database: process.env.DB_NAME, // e.g. 'my-database'
    socketPath: process.env.INSTANCE_UNIX_SOCKET, // e.g. '/cloudsql/project:region:instance'
    // Specify additional properties here.
    ...config,
  });
};

using MySql.Data.MySqlClient;
using System;

namespace CloudSql
{
    public class MySqlUnix
    {
        public static MySqlConnectionStringBuilder NewMysqlUnixSocketConnectionString()
        {
            // Equivalent connection string:
            // "Server=<INSTANCE_UNIX_SOCKET>;Uid=<DB_USER>;Pwd=<DB_PASS>;Database=<DB_NAME>;Protocol=unix"
            var connectionString = new MySqlConnectionStringBuilder()
            {
                // The Cloud SQL proxy provides encryption between the proxy and instance.
                SslMode = MySqlSslMode.Disabled,

                // Note: Saving credentials in environment variables is convenient, but not
                // secure - consider a more secure solution such as
                // Cloud Secret Manager (https://cloud.google.com/secret-manager) to help
                // keep secrets safe.
                Server = Environment.GetEnvironmentVariable("INSTANCE_UNIX_SOCKET"), // e.g. '/cloudsql/project:region:instance'
                UserID = Environment.GetEnvironmentVariable("DB_USER"),   // e.g. 'my-db-user
                Password = Environment.GetEnvironmentVariable("DB_PASS"), // e.g. 'my-db-password'
                Database = Environment.GetEnvironmentVariable("DB_NAME"), // e.g. 'my-database'
                ConnectionProtocol = MySqlConnectionProtocol.UnixSocket
            };
            connectionString.Pooling = true;
            // Specify additional properties here.
            return connectionString;
        }
    }
}

package cloudsql

import (
	"database/sql"
	"fmt"
	"log"
	"os"

	_ "github.com/go-sql-driver/mysql"
)

// connectUnixSocket initializes a Unix socket connection pool for
// a Cloud SQL instance of MySQL.
func connectUnixSocket() (*sql.DB, error) {
	mustGetenv := func(k string) string {
		v := os.Getenv(k)
		if v == "" {
			log.Fatalf("Fatal Error in connect_unix.go: %s environment variable not set.", k)
		}
		return v
	}
	// Note: Saving credentials in environment variables is convenient, but not
	// secure - consider a more secure solution such as
	// Cloud Secret Manager (https://cloud.google.com/secret-manager) to help
	// keep secrets safe.
	var (
		dbUser         = mustGetenv("DB_USER")              // e.g. 'my-db-user'
		dbPwd          = mustGetenv("DB_PASS")              // e.g. 'my-db-password'
		dbName         = mustGetenv("DB_NAME")              // e.g. 'my-database'
		unixSocketPath = mustGetenv("INSTANCE_UNIX_SOCKET") // e.g. '/cloudsql/project:region:instance'
	)

	dbURI := fmt.Sprintf("%s:%s@unix(%s)/%s?parseTime=true",
		dbUser, dbPwd, unixSocketPath, dbName)

	// dbPool is the pool of database connections.
	dbPool, err := sql.Open("mysql", dbURI)
	if err != nil {
		return nil, fmt.Errorf("sql.Open: %w", err)
	}

	// ...

	return dbPool, nil
}

unix: &unix
  adapter: mysql2
  # Configure additional properties here.
  # Note: Saving credentials in environment variables is convenient, but not
  # secure - consider a more secure solution such as
  # Cloud Secret Manager (https://cloud.google.com/secret-manager) to help
  # keep secrets safe.
  username: <%= ENV["DB_USER"] %>  # e.g. "my-database-user"
  password: <%= ENV["DB_PASS"] %> # e.g. "my-database-password"
  database: <%= ENV.fetch("DB_NAME") { "vote_development" } %>
  # Specify the Unix socket path as host
  socket: "<%= ENV["INSTANCE_UNIX_SOCKET"] %>"

namespace Google\Cloud\Samples\CloudSQL\MySQL;

use PDO;
use PDOException;
use RuntimeException;
use TypeError;

class DatabaseUnix
{
    public static function initUnixDatabaseConnection(): PDO
    {
        try {
            // Note: Saving credentials in environment variables is convenient, but not
            // secure - consider a more secure solution such as
            // Cloud Secret Manager (https://cloud.google.com/secret-manager) to help
            // keep secrets safe.
            $username = getenv('DB_USER'); // e.g. 'your_db_user'
            $password = getenv('DB_PASS'); // e.g. 'your_db_password'
            $dbName = getenv('DB_NAME'); // e.g. 'your_db_name'
            $instanceUnixSocket = getenv('INSTANCE_UNIX_SOCKET'); // e.g. '/cloudsql/project:region:instance'

            // Connect using UNIX sockets
            $dsn = sprintf(
                'mysql:dbname=%s;unix_socket=%s',
                $dbName,
                $instanceUnixSocket
            );

            // Connect to the database.
            $conn = new PDO(
                $dsn,
                $username,
                $password,
                # ...
            );
        } catch (TypeError $e) {
            throw new RuntimeException(
                sprintf(
                    'Invalid or missing configuration! Make sure you have set ' .
                        '$username, $password, $dbName, ' .
                        'and $instanceUnixSocket (for UNIX socket mode). ' .
                        'The PHP error was %s',
                    $e->getMessage()
                ),
                (int) $e->getCode(),
                $e
            );
        } catch (PDOException $e) {
            throw new RuntimeException(
                sprintf(
                    'Could not connect to the Cloud SQL Database. Check that ' .
                        'your username and password are correct, that the Cloud SQL ' .
                        'proxy is running, and that the database exists and is ready ' .
                        'for use. For more assistance, refer to %s. The PDO error was %s',
                    'https://cloud.google.com/sql/docs/mysql/connect-external-app',
                    $e->getMessage()
                ),
                (int) $e->getCode(),
                $e
            );
        }

        return $conn;
    }
}

import os

from google.cloud.sql.connector import Connector, IPTypes
import pymysql

import sqlalchemy


def connect_with_connector() -> sqlalchemy.engine.base.Engine:
    """
    Initializes a connection pool for a Cloud SQL instance of MySQL.

    Uses the Cloud SQL Python Connector package.
    """
    # Note: Saving credentials in environment variables is convenient, but not
    # secure - consider a more secure solution such as
    # Cloud Secret Manager (https://cloud.google.com/secret-manager) to help
    # keep secrets safe.

    instance_connection_name = os.environ[
        "INSTANCE_CONNECTION_NAME"
    ]  # e.g. 'project:region:instance'
    db_user = os.environ["DB_USER"]  # e.g. 'my-db-user'
    db_pass = os.environ["DB_PASS"]  # e.g. 'my-db-password'
    db_name = os.environ["DB_NAME"]  # e.g. 'my-database'

    ip_type = IPTypes.PRIVATE if os.environ.get("PRIVATE_IP") else IPTypes.PUBLIC

    connector = Connector(ip_type)

    def getconn() -> pymysql.connections.Connection:
        conn: pymysql.connections.Connection = connector.connect(
            instance_connection_name,
            "pymysql",
            user=db_user,
            password=db_pass,
            db=db_name,
        )
        return conn

    pool = sqlalchemy.create_engine(
        "mysql+pymysql://",
        creator=getconn,
        # ...
    )
    return pool

import com.zaxxer.hikari.HikariConfig;
import com.zaxxer.hikari.HikariDataSource;
import javax.sql.DataSource;

public class ConnectorConnectionPoolFactory extends ConnectionPoolFactory {

  // Note: Saving credentials in environment variables is convenient, but not
  // secure - consider a more secure solution such as
  // Cloud Secret Manager (https://cloud.google.com/secret-manager) to help
  // keep secrets safe.
  private static final String INSTANCE_CONNECTION_NAME =
      System.getenv("INSTANCE_CONNECTION_NAME");
  private static final String INSTANCE_UNIX_SOCKET = System.getenv("INSTANCE_UNIX_SOCKET");
  private static final String DB_USER = System.getenv("DB_USER");
  private static final String DB_PASS = System.getenv("DB_PASS");
  private static final String DB_NAME = System.getenv("DB_NAME");

  public static DataSource createConnectionPool() {
    // The configuration object specifies behaviors for the connection pool.
    HikariConfig config = new HikariConfig();

    // The following URL is equivalent to setting the config options below:
    // jdbc:mysql:///<DB_NAME>?cloudSqlInstance=<INSTANCE_CONNECTION_NAME>&
    // socketFactory=com.google.cloud.sql.mysql.SocketFactory&user=<DB_USER>&password=<DB_PASS>
    // See the link below for more info on building a JDBC URL for the Cloud SQL JDBC Socket Factory
    // https://github.com/GoogleCloudPlatform/cloud-sql-jdbc-socket-factory#creating-the-jdbc-url

    // Configure which instance and what database user to connect with.
    config.setJdbcUrl(String.format("jdbc:mysql:///%s", DB_NAME));
    config.setUsername(DB_USER); // e.g. "root", "mysql"
    config.setPassword(DB_PASS); // e.g. "my-password"

    config.addDataSourceProperty("socketFactory", "com.google.cloud.sql.mysql.SocketFactory");
    config.addDataSourceProperty("cloudSqlInstance", INSTANCE_CONNECTION_NAME);


    // The ipTypes argument can be used to specify a comma delimited list of preferred IP types
    // for connecting to a Cloud SQL instance. The argument ipTypes=PRIVATE will force the
    // SocketFactory to connect with an instance's associated private IP.
    config.addDataSourceProperty("ipTypes", "PUBLIC,PRIVATE");

    // ... Specify additional connection properties here.
    // ...

    // Initialize the connection pool using the configuration object.
    return new HikariDataSource(config);
  }
}

package cloudsql

import (
	"context"
	"database/sql"
	"fmt"
	"log"
	"net"
	"os"

	"cloud.google.com/go/cloudsqlconn"
	"github.com/go-sql-driver/mysql"
)

func connectWithConnector() (*sql.DB, error) {
	mustGetenv := func(k string) string {
		v := os.Getenv(k)
		if v == "" {
			log.Fatalf("Fatal Error in connect_connector.go: %s environment variable not set.", k)
		}
		return v
	}
	// Note: Saving credentials in environment variables is convenient, but not
	// secure - consider a more secure solution such as
	// Cloud Secret Manager (https://cloud.google.com/secret-manager) to help
	// keep passwords and other secrets safe.
	var (
		dbUser                 = mustGetenv("DB_USER")                  // e.g. 'my-db-user'
		dbPwd                  = mustGetenv("DB_PASS")                  // e.g. 'my-db-password'
		dbName                 = mustGetenv("DB_NAME")                  // e.g. 'my-database'
		instanceConnectionName = mustGetenv("INSTANCE_CONNECTION_NAME") // e.g. 'project:region:instance'
		usePrivate             = os.Getenv("PRIVATE_IP")
	)

	d, err := cloudsqlconn.NewDialer(context.Background())
	if err != nil {
		return nil, fmt.Errorf("cloudsqlconn.NewDialer: %w", err)
	}
	var opts []cloudsqlconn.DialOption
	if usePrivate != "" {
		opts = append(opts, cloudsqlconn.WithPrivateIP())
	}
	mysql.RegisterDialContext("cloudsqlconn",
		func(ctx context.Context, addr string) (net.Conn, error) {
			return d.Dial(ctx, instanceConnectionName, opts...)
		})

	dbURI := fmt.Sprintf("%s:%s@cloudsqlconn(localhost:3306)/%s?parseTime=true",
		dbUser, dbPwd, dbName)

	dbPool, err := sql.Open("mysql", dbURI)
	if err != nil {
		return nil, fmt.Errorf("sql.Open: %w", err)
	}
	return dbPool, nil
}