Creating read replicas

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. You create a replica to offload read requests or analytics traffic from the primary. You can create multiple read replicas for a single primary instance.

Read replicas are read-only. You cannot write to them.

For more information about how replication works, see Requirements and Tips for Configuring Replication.

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.

Creating a read replica

The steps for creating a read replica are below.

Console

  1. Go to the Cloud SQL Instances page in the Google Cloud Console.

    Go to the Cloud SQL Instances page

  2. Find the instance you want to create a replica for, and open its more actions menu at the far right of the listing.
  3. Select Create read replica.

    If you do not see that choice, the instance is a replica; you cannot create a replica of a replica.

  4. If the instance had backups and binary logging enabled, continue with step 6. Otherwise, select Automate backups and Enable binary logging, click Continue, and then click Save and restart to restart the instance.

    Enabling binary logging causes the instance to be restarted.

  5. In the Create read replica page, update the instance ID, if needed, and any other configuration options required, including name, region, and zone.
  6. Click Create.

    Cloud SQL creates a backup, if needed, and creates the replica. You are returned to the instance page for the primary.

gcloud

  1. Check the status of the primary instance:
    gcloud sql instances describe [PRIMARY_INSTANCE_NAME]

    If the databaseReplicationEnabled property is true, the instance is a replica; you cannot create a replica of a replica.

  2. If the enabled property under backupConfiguration is false, enable backups for the primary instance now:
    gcloud sql instances patch [PRIMARY_INSTANCE_NAME] --backup-start-time [HH:MM]
    The backup-start-time parameter is specified in 24-hour time, in the UTC±00 time zone, and specifies the start of a 4-hour backup window. Backups can start any time during the backup window.
  3. If the binaryLogEnabled property is false, enable binary logs:
    gcloud sql instances patch --enable-bin-log [PRIMARY_INSTANCE_NAME]
    Enabling binary logs causes the instance to be restarted.
  4. Create the replica:
    gcloud sql instances create [REPLICA_NAME] --master-instance-name=[PRIMARY_INSTANCE_NAME]
    

    You can specify a different tier size using the --tier parameter, if needed.

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

    If the primary instance has a private IP address only, add the --no-assign-ip parameter to the command.

REST

  1. Get the current backup configuration

    Use the get method of the instances resource to return the database version and current backup configuration for the primary.

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

    • project-id: The project ID
    • primary-instance-name: The name of the primary instance

    HTTP method and URL:

    GET https://www.googleapis.com/sql/v1beta4/projects/project-id/instances/primary-instance-name

    To send your request, expand one of these options:

    You should receive a JSON response similar to the following:

  2. Verify that the replication fields are set

    If either enabled or binaryLogEnabled are false, use the patch method of the instances resource to enable them both. In the request, specify any properties of the backup configuration that you want to change.

    To enable backups, set enabled to true and the startTime to a time of day in HH:MM format. The startTime parameter is specified in 24-hour time, in the UTC±00 time zone, and specifies the start of a 4-hour backup window. Backups can start any time during the backup window.

    To enable point-in-time recovery, set binaryLogEnabled to true.

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

    • project-id: The project ID
    • instance-id: The instance ID
    • start-time The time in the format "HH:MM"

    HTTP method and URL:

    PATCH https://www.googleapis.com/sql/v1beta4/projects/project-id/instances/instance-id

    Request JSON body:

    {
      "settings":
      {
        "backupConfiguration":
        {
          "startTime": "start-time",
          "enabled": true,
          "binaryLogEnabled": true
        }
      }
    }
    

    To send your request, expand one of these options:

    You should receive a JSON response similar to the following:

  3. Create the read replica

    Use the insert method of the instances resource to create the read replica. The databaseVersion property must be the same as the primary. For a cross-region read replica, specify a region other than the primary instance's region.

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

    • project-id: The project ID
    • 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 (tier) type. For example: "db-n1-standard-4"

    HTTP method and URL:

    POST https://www.googleapis.com/sql/v1beta4/projects/project-id/instances

    Request JSON body:

    {
      "masterInstanceName": "primary-instance-name",
      "project": "project-id",
      "name": "replica-name",
      "region": "replica-region",
      "settings":
      {
        "tier": "machine-type",
        "settingsVersion": 0,
      }
    }
    

    To send your request, expand one of these options:

    You should receive a JSON response similar to the following:

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