Create read replicas

MySQL | PostgreSQL | SQL Server

This page describes how to create a read replica for a Cloud SQL instance.

A read replica is a copy of the primary instance that reflects changes to the primary in almost real time, in normal circumstances. You can use a read replica to offload read requests or analytics traffic from the primary instance.

Additionally, for disaster recovery, you can perform a regional migration. If a replica is a cross-region replica, you can perform a failover to another region; specifically, you can promote a replica to a standalone instance (in which case, existing replicas would not consider that instance as primary).

For more information about how replication works, see Replication in Cloud SQL.

Before you begin

If you are creating the first replica for this instance, ensure that the instance meets the requirements for primary instances. Learn more.

Create a read replica

The steps for creating a read replica are below.

Console

In the Google Cloud console, go to the Cloud SQL Instances page.

Go to Cloud SQL Instances
Find the instance for which you want to create a replica, and then open the more actions menu next to the listing.
Select Create read replica.
If you don't see that choice, then the instance is a replica; you can't create a replica of a replica.
In the Customize your instance section of the page, update settings for your replica. Begin by clicking Show configuration options to display the groups of settings. Then, expand the desired groups to review and customize the settings. A Summary of all the options you select appears on the right. Customizing these settings is optional. Defaults are assigned in every case where no customizations are made.

For more details about each setting, see the About instance settings page.

For example, to allow other Google Cloud services, such as BigQuery, to access data in Cloud SQL and make queries against this data over an internal connection, expand the Connections group, and then deselect the Public IP check box.
Click Create replica.
Cloud SQL creates a backup, if needed, and creates the replica. You are returned to the instance page for the primary.

gcloud

Create the replica:

gcloud sql instances create REPLICA_NAME \
--master-instance-name=MASTER_INSTANCE_NAME

You can specify a different tier size using the --tier parameter, if needed. Also, if you're creating a replica from a primary instance, and the Cloud SQL edition for the instance is either Enterprise or is Enterprise Plus, version 16 and later, then you don't have to specify a value for this parameter. The replica inherits the machine type from the primary instance.

You can specify a different region using the --region parameter.

If the primary instance has an internal IP address only, and you want to allow other Google Cloud services, such as BigQuery, to access data in Cloud SQL and make queries against this data over an internal connection, then add the --enable-google-private-path parameter to the command.

You must create the replica in the same VPC network as the primary instance. You can also specify an allocated-ip-range-name in that VPC network. If no range is specified, the replica is created in a random range.

Terraform

To create a read replica, use a Terraform resource.

resource "google_sql_database_instance" "read_replica" {
  name                 = "postgres-replica-instance-name"
  master_instance_name = google_sql_database_instance.primary.name
  region               = "europe-west4"
  database_version     = "POSTGRES_14"

  settings {
    tier              = "db-custom-2-7680"
    availability_type = "ZONAL"
    disk_size         = "100"
  }
  # set `deletion_protection` to true, will ensure that one cannot accidentally delete this instance by
  # use of Terraform whereas `deletion_protection_enabled` flag protects this instance at the GCP level.
  deletion_protection = false
}

REST v1

Use the insert method of the instances resource to create the read replica. The region and databaseVersion properties must be the same as the master.

Before using any of the request data, make the following replacements:

project-id: The project ID
database-version: Enum version string (for example, POSTGRES_12)
primary-instance-name: The name of the primary instance
primary-instance-region: The region of the primary instance
replica-region: The region of the replica instance
replica-name: The name of the replica instance
machine-type: Enum string of the machine type. For example: "db-custom-1-3840"
private-network: The authorized network that you're adding or selecting to create a private connection.

You set the value of the ipv4Enabled parameter to false because you want the Cloud SQL instance to be associated with a private IP address, not a public IP one.

You can use the sqlNetworkArchitecture field to enforce the use of the new network architecture for the instance upon creation, even if the project isn't fully upgraded. For more details about the new network architecture and its implications, see Upgrade an instance to the new network architecture and Allocate an IP address range.

HTTP method and URL:

POST https://sqladmin.googleapis.com/v1/projects/project-id/instances

Request JSON body:

{
  "masterInstanceName": "primary-instance-name",
  "project": "project-id",
  "databaseVersion": "database-version",
  "name": "replica-name",
  "region": "replica-region",
  "settings":
  {
    "tier": "machine-type",
    "settingsVersion": 0,
    "ipConfiguration": {
    object (IpConfiguration)
  },
  {
  "ipv4Enabled": false,
  "privateNetwork": private-network,
  "requireSsl": boolean,
  "authorizedNetworks": [
    {
      object (AclEntry)
    }
  ],
  "allocatedIpRange": string
    }
  },
  "sqlNetworkArchitecture": "NEW_NETWORK_ARCHITECTURE"
}

To send your request, expand one of these options:

curl (Linux, macOS, or Cloud Shell)

Note: The following command assumes that you have logged in to the gcloud CLI with your user account by running gcloud init or gcloud auth login , or by using Cloud Shell, which automatically logs you into the gcloud CLI . You can check the currently active account by running gcloud auth list.

Save the request body in a file named request.json, and execute the following command:

curl -X POST \
     -H "Authorization: Bearer $(gcloud auth print-access-token)" \
     -H "Content-Type: application/json; charset=utf-8" \
     -d @request.json \
     "https://sqladmin.googleapis.com/v1/projects/project-id/instances"

PowerShell (Windows)

Note: The following command assumes that you have logged in to the gcloud CLI with your user account by running gcloud init or gcloud auth login . You can check the currently active account by running gcloud auth list.