This module allows you to configure a number of parameters, such as backup windows, maintenance window, replicas and encryption. For a list of all available variables and their descriptions, see variables.tf.

How do you connect to the database?

Cloud SQL instances are created in a producer network (a VPC network internal to Google). They are not created in your VPC network. See https://cloud.google.com/sql/docs/mysql/private-ip

You can use both public IP and private IP to connect to a Cloud SQL instance. Neither connection method affects the other; you must protect the public IP connection whether the instance is configured to use private IP or not.

You can also use the Cloud SQL Proxy to connect to an instance that is also configured to use private IP. The proxy can connect using either the private IP address or a public IP address.

This module provides the connection details as Terraform output variables:

First IP Address first_ip_address: The first IPv4 address of the addresses assigned to the instance. If the instance has only public IP, it is the public IP address. If it has only private IP, it the private IP address. If it has both, it is the first item in the list and full IP address details are in instance_ip_addresses.
Proxy connection proxy_connection: Instance path for connecting with Cloud SQL Proxy; see Connecting mysql Client Using the Cloud SQL Proxy.
TODO: Replica endpoints replica_endpoints: A comma-separated list of all DB instance URLs in the cluster, including the primary and all read replicas. Use these URLs for reads (see "How do you scale this DB?" below).

You can programmatically extract these variables in your Terraform templates and pass them to other resources. You'll also see the variables at the end of each terraform apply call or if you run terraform output.

For full connectivity options and detailed documentation, see Connecting to Cloud SQL from External Applications.

How do you scale this database?

Storage: Cloud SQL manages storage for you, automatically growing cluster volume up to 10TB.
Vertical scaling: To scale vertically (i.e. bigger DB instances with more CPU and RAM), use the machine_type input variable. For a list of Cloud SQL Machine Types, see Cloud SQL Pricing.
Horizontal scaling: To scale horizontally, you can add more replicas using the instance_count input variable, and the module will automatically deploy the new instances, sync them to the master, and make them available as read replicas.

Known Issues

Instance Recovery

Due to limitations on the current terraform provider for Google, it is not possible to restore backups with terraform.

See https://github.com/terraform-providers/terraform-provider-google/issues/2446

Read Replica and IP Addresses Outputs

Retrieving and outputting distinct values from list of maps is not possible with resources using count prior to terraform 0.12. Instead we have to output the values JSON encoded - for example read_replica_server_ca_certs. For full details of the outputs and their format, see outputs.tf.

See https://github.com/hashicorp/terraform/issues/17048