Connecting from Cloud Functions to Cloud SQL

This page contains information and examples for connecting to a Cloud SQL instance from a service running in Cloud Functions.

Cloud SQL is a fully-managed database service that helps you set up, maintain, manage, and administer your relational databases in the cloud.

Cloud Functions is a lightweight compute solution for developers to create single-purpose, standalone functions that responds to Cloud events without the need to manage a server or runtime environment.

Setting up a Cloud SQL instance

  1. Enable the Cloud SQL Admin API in the project you are connecting from, if you haven't already done so:

    Enable the API

  2. Create a Cloud SQL for SQL Server instance.

    By default, Cloud SQL assigns a public IP address to a new instance. Cloud Functions does not support connecting to Cloud SQL for SQL Server over public IP. Use private IP instead. For more information, see Configuring private IP.

Configuring Cloud Functions

The steps to configure Cloud Functions depend on the type of IP address you assigned to your Cloud SQL instance.

Public IP (default)

Cloud Functions does not support connecting to Cloud SQL for SQL Server over public IP. Use private IP instead.

Private IP

A Serverless VPC Access connector handles communication to your VPC network. To connect directly with private IP, you need to:

  1. Make sure that the Cloud SQL instance created above has a private IP address. If you need to add one, see the Configuring private IP page for instructions.
  2. Create a Serverless VPC Access connector in the same VPC network as your Cloud SQL instance.
  3. Unless you're using Shared VPC, a connector must be in the same project and region as the resource that uses it, but the connector can send traffic to resources in different regions.

    Serverless VPC Access supports communication to VPC networks connected via Cloud VPN and VPC Network Peering.

    Serverless VPC Access does not support legacy networks.

  4. Configure Cloud Functions to use the connector.
  5. Connect using your instance's private IP and port 1433.

Connecting to Cloud SQL

After you configure Cloud Functions, you can connect to your Cloud SQL instance.

Public IP (default)

Cloud Functions does not support connecting to Cloud SQL for SQL Server over public IP. Use private IP instead.

For public IP paths, Cloud Functions provides encryption and connects using the Cloud SQL Auth proxy through Unix sockets.

Private IP

For private IP paths, your application will connect directly to your instance through Serverless VPC Access. This method uses TCP to connect directly to the Cloud SQL instance without using the Cloud SQL Auth proxy.

Connect with TCP

Connect directly using the private IP address and port 1433 for your instance.


To see this snippet in the context of a web application, view the README on GitHub.

# Remember - storing secrets in plaintext is potentially unsafe. Consider using
# something like to help keep
# secrets secret.
db_user = os.environ["DB_USER"]
db_pass = os.environ["DB_PASS"]
db_name = os.environ["DB_NAME"]
db_host = os.environ["DB_HOST"]

# Extract host and port from environment variable DB_HOST
host_args = db_host.split(":")
db_hostname, db_port = host_args[0], int(host_args[1])

# SQL Server drivers don't account for this
if db_hostname == "localhost":
    db_hostname = ""

# The SQLAlchemy engine will help manage interactions, including automatically
# managing a pool of connections to your database
pool = sqlalchemy.create_engine(
    # Equivalent URL:
    # mssql+pytds://<db_user>:<db_pass>@/<host>:<port>/<db_name>?driver=ODBC+Driver+17+for+SQL+Server


To see this snippet in the context of a web application, view the README on GitHub.


  • Using the argument ipTypes=PRIVATE will force the SocketFactory to connect with an instance's associated private IP
  • See the JDBC socket factory version requirements for the pom.xml file here .

// Note: For Java users, the Cloud SQL JDBC Socket Factory can provide authenticated connections
// which is preferred to using the Cloud SQL Proxy with Unix sockets.
// See for details.

// The configuration object specifies behaviors for the connection pool.
HikariConfig config = new HikariConfig();

// The following is equivalent to setting the config options below:
// jdbc:sqlserver://;user=<DB_USER>;password=<DB_PASS>;databaseName=<DB_NAME>;
// socketFactoryConstructorArg=<CLOUD_SQL_CONNECTION_NAME>

// See the link below for more info on building a JDBC URL for the Cloud SQL JDBC Socket Factory

// Configure which instance and what database user to connect with.
config.setUsername(DB_USER); // e.g. "root", "sqlserver"
config.setPassword(DB_PASS); // e.g. "my-password"
config.addDataSourceProperty("databaseName", DB_NAME);

config.addDataSourceProperty("socketFactoryConstructorArg", CLOUD_SQL_CONNECTION_NAME);

// ... Specify additional connection properties here.

// ...

// Initialize the connection pool using the configuration object.
DataSource pool = new HikariDataSource(config);


To see this snippet in the context of a web application, view the README on GitHub.

const createPool = async () => {
  const config = {pool: {}};
  config.user = process.env.DB_USER; // e.g. 'my-db-user'
  config.password = process.env.DB_PASS; // e.g. 'my-db-password'
  config.database = process.env.DB_NAME; // e.g. 'my-database'
  // set the server to '' when connecting from App Engine Flex
  config.server = process.env.DEPLOYED ? '' : '';
  config.port = 1433;

  // ...
  return await mssql.connect(config);


To see this snippet in the context of a web application, view the README on GitHub.

var (
	dbUser    = mustGetenv("DB_USER") // e.g. 'my-db-user'
	dbPwd     = mustGetenv("DB_PASS") // e.g. 'my-db-password'
	dbTCPHost = mustGetenv("DB_HOST") // e.g. '' ('' if deployed to GAE Flex)
	dbPort    = mustGetenv("DB_PORT") // e.g. '1433'
	dbName    = mustGetenv("DB_NAME") // e.g. 'my-database'

var dbURI string
dbURI = fmt.Sprintf("server=%s;user id=%s;password=%s;port=%s;database=%s;", dbTCPHost, dbUser, dbPwd, dbPort, dbName)

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

// ...

return dbPool, nil


To see this snippet in the context of a web application, view the README on GitHub.

// $username = 'your_db_user';
// $password = 'yoursupersecretpassword';
// $dbName = 'your_db_name';
// $dbHost = "";

// Connect using TCP
$dsn = sprintf('sqlsrv:server=%s;Database=%s', $dbHost, $dbName);

// Connect to the database
$conn = new PDO($dsn, $username, $password, $connConfig);

Best practices and other information

You can use the Cloud SQL Auth proxy when testing your application locally. See the quickstart for using the Cloud SQL Auth proxy for detailed instructions.

Connection Pools

Connections to underlying databases may be dropped, either by the database server itself, or by the infrastructure underlying Cloud Functions. We recommend using a client library that supports connection pools that automatically reconnect broken client connections. Additionally, we recommend using a globally scoped connection pool to increase the likelihood that your function reuses the same connection for subsequent invocations of the function, and closes the connection naturally when the instance is evicted (auto-scaled down). For more detailed examples on how to use connection pools, see Managing database connections.

Connection Limits

Cloud SQL imposes a maximum limit on concurrent connections, and these limits may vary depending on the database engine chosen (see Cloud SQL Quotas and Limits). It's recommended to use a connection with Cloud Functions, but it is important to set the maximum number of connections to 1.

Where possible, you should take care to only initialize a connection pool for functions that need access to your database. Some connection pools will create connections preemptively, which can consume excess resources and count towards your connection limits. For this reason, it's recommended to use Lazy Initialization to delay the creation of a connection pool until needed, and only include the connection pool in functions where it's used.

For more detailed examples on how to limit the number of connections, see Managing database connections.

API Quota Limits

Cloud Functions provides a mechanism that connects using the Cloud SQL Auth proxy, which uses the Cloud SQL Admin API. API quota limits apply to the Cloud SQL Auth proxy. The Cloud SQL Admin API quota used is approximately two times the number of Cloud SQL instances configured times the total number of functions deployed. You can set the number of max concurrent invocations to modify the expected API quota consumed. Cloud Functions also imposes rate limits on the number of API calls allowed per 100 seconds.