Working with cross-region replication

This page describes how to use cross-region replication by creating and working with secondary clusters.

For a conceptual overview of cross-region replication, see About cross-region replication.

Before you begin

• The Google Cloud project you are using must have been enabled to access AlloyDB.
• You must have one of these IAM roles in the Google Cloud project you are using:
  • roles/alloydb.admin (the AlloyDB Admin predefined IAM role)
  • roles/owner (the Owner basic IAM role)
  • roles/editor (the Editor basic IAM role)

  If you don't have any of these roles, contact your Organization Administrator to request access.

Create a secondary cluster

When you create a secondary cluster, AlloyDB copies and applies some of the primary cluster configuration onto the secondary cluster. AlloyDB does not copy read pools, encryption configuration, point-in-time recovery (PITR), and backup configuration onto the secondary cluster.

If you update the primary cluster configuration after you create the secondary cluster, the changes are not available on the secondary cluster. However, you can manually update the secondary cluster to have the latest configuration that's available in the primary cluster.

Note: Secondary clusters do not support backups, and you cannot apply your primary cluster's backup configurations on secondary clusters after you create them. However, you can configure automated and continuous backups after you promote secondary clusters.

To create an AlloyDB secondary cluster and secondary instance, follow these steps:

Console

1. In the Google Cloud console, go to the Clusters page.

   Go to Clusters

2. Click a cluster in the Resource Name column.

3. In the Overview page, click Create secondary cluster.

4. Configure your secondary cluster:

   1. In the Cluster ID field, enter a resource ID for your secondary cluster.
   2. Select a region for your secondary cluster that is different from the primary cluster region.
   3. Select the default Google-managed encryption or a customer-managed key (CMEK) as an encryption method to encrypt your secondary cluster.

   If you want to encrypt this cluster using CMEK key, follow these steps:

   1. Click Advanced encryption options.
   2. Select Customer-managed encryption key (CMEK).

   3. Select a customer-managed key from the menu that appears.

      The Google Cloud console limits this list to keys within the same Google Cloud project and region as the new cluster.

      To use a key that is not on this list, follow these steps:

      1. Click Don't see your key? Enter key resource name.
      2. Enter the resource name in the Key resource name field.
      3. Click Save.
      4. Click Continue.

   Using CMEK key with AlloyDB requires some additional setup. For more information, see Use CMEK.

   If the associated primary instance is encrypted with a CMEK key, you must also encrypt its secondary cluster with a CMEK key.

5. Configure your secondary instance:

   1. In the Instance ID field, enter a resource ID for your secondary instance. The resource ID must be unique within a cluster.

6. Click Create cluster.

gcloud

To use the gcloud CLI, you can install and initialize the Google Cloud CLI, or you can use Cloud Shell.

Use the gcloud alloydb clusters create-secondary command:

 gcloud alloydb clusters create-secondary SECONDARY_CLUSTER_ID \
 --region=REGION_ID \
 --primary-cluster=PRIMARY_CLUSTER_ID \
 gcloud alloydb instances create-secondary SECONDARY_INSTANCE_ID \
 --cluster=SECONDARY_CLUSTER_ID \
 --region=REGION_ID \

Replace the following:

• SECONDARY_CLUSTER_ID: The ID of the secondary cluster that you want to create.
• SECONDARY_INSTANCE_ID: The ID of the secondary instance that you want to create.
• REGION_ID: The ID of the secondary cluster's region—for example, us-central1.
• PROJECT_ID: The ID of the secondary cluster's project.
• PRIMARY_CLUSTER_ID: The ID of the primary cluster that the secondary cluster is associated with.
• SECONDARY_CLUSTER_ID: The ID of the secondary cluster that the secondary instance is associated with.

View a secondary cluster

To view detailed information about an AlloyDB secondary cluster, follow these steps:

1. In the Google Cloud console, go to the Clusters page.

   Go to Clusters

2. Click a secondary cluster in the Resource Name column.

3. In the Overview page, view all details about your secondary cluster.

Update a secondary instance

You can update a secondary instance to add, modify, or delete database flags. You can also scale your secondary instance's machine type.

Configure database flags on a secondary instance

To add, modify, or delete database flags, complete the following steps:

Console

1. In the Google Cloud console, go to the Clusters page.

   Go to Clusters

2. In the Resource Name column, click a secondary cluster that you want to modify.

3. In the Overview page, go to Instances in your cluster, select the secondary instance, and then click Edit secondary.

4. Add, modify, or delete a database flag from your instance:

   Add a flag

   1. To add a database flag to your instance, click Add flag.
   2. Select a flag from the New database flag list.
   3. Provide a value for the flag.
   4. Click Done.

   Modify a flag

   1. To modify a database flag present in your instance, expand the database flag and modify the value of the existing flag in the Edit database flag section.
   2. Click Done.

   Delete a flag

   1. To delete a database flag from your instance, select a flag and click the delete icon.
   2. Click Done.

5. Click Update secondary.

gcloud

Use the gcloud alloydb instances update command to change the database flags for a secondary instance.

Caution: Running the following command overwrites all database flags that are previously set. Any database flags that are not explicitly included in the --database-flags list are reset to its default value. To retain your instance's database flags while adding new flags, you must include both current and new flags in the --database-flags list.

 gcloud alloydb instances update SECONDARY_INSTANCE_ID \
  --database-flags FLAGS_LIST \
  --region=REGION_ID \
  --cluster=CLUSTER_ID \
  --project=PROJECT_ID

Replace the following:

• SECONDARY_INSTANCE_ID: The ID of the secondary instance.
• FLAGS_LIST: A comma-separated list of one or more database flag specifications. Each specification consists of the name of the flag, an equals sign (=), and the value to assign to the flags. For database flags that do not take values, provide the name of the flag followed by an equals sign (=).
• REGION_ID: The region where the secondary instance is placed—for example, us-central1.
• CLUSTER_ID: The ID of the cluster where the secondary instance is placed.
• PROJECT_ID: The ID of the project where the secondary cluster is placed.

Scale your secondary instance's machine type

To scale your secondary instance's machine type, complete the following steps:

Console

1. In the Google Cloud console, go to the Clusters page.

   Go to Clusters

2. In the Resource Name column, click a secondary cluster that you want to modify.

3. In the Overview page, go to the Instances in your cluster section, and click Edit secondary.

   Note that this action is not available if the page reports a cluster Status of Maintenance. The action becomes available again after Status changes to Ready.

4. Select a machine type.

5. Click Update secondary.

gcloud

Use the gcloud alloydb instances update command to change the machine type of the secondary instance.

 gcloud alloydb instances update SECONDARY_INSTANCE_ID \
  --cpu-count=CPU_COUNT \
  --region=REGION_ID \
  --cluster=CLUSTER_ID \
  --project=PROJECT_ID

Replace the following:

• SECONDARY_INSTANCE_ID: The ID of the secondary instance that you are updating.

• CPU_COUNT: The number of vCPUs you want for the instance. Valid values include:

  • 2 (2 vCPUs, 16 GB RAM)
  • 4 (4 vCPUs, 32 GB RAM)
  • 8 (8 vCPUs, 64 GB RAM)
  • 16 (16 vCPUs, 128 GB RAM)
  • 32 (32 vCPUs, 256 GB RAM)
  • 64 (64 vCPUs, 512 GB RAM)

• REGION_ID: The region where the instance is placed.

• CLUSTER_ID: The ID of the cluster where the instance is placed.

• PROJECT_ID: The ID of the project where the cluster is placed.

If the command returns an error message that includes the phrase invalid cluster state MAINTENANCE, then the cluster is undergoing routine maintenance. This temporarily disallows instance reconfiguration. Run the command again after the cluster returns to a READY state.

To check the cluster's status, see View cluster details.

Add read pool instances to a secondary cluster

To add a read pool instance to a secondary cluster, follow these steps:

1. In the Google Cloud console, go to the Clusters page.

   Go to Clusters

2. In the Resource Name column, click a secondary cluster to which you want to add a read pool instance.

3. In the Overview page, go to the Instances in your cluster section, and click Add read pool.

4. Configure your read pool instance:

   1. In the Read pool instance ID field, enter an ID for the read pool instance.
   2. In the Node count field, enter a node count. The number of nodes in a read pool instance determines the instance's overall computing capacity. You can have a maximum of 20 nodes across all the read pool instances in a cluster.
   3. Select a machine type.

   4. Optional: Set custom flags to your instance. For each flag, do the following:

      1. Click Add flag.
      2. Select a flag from the New database flag list.
      3. Provide a value for the flag.
      4. Click Done.

5. Click Add read pool.

Promote a secondary cluster

Before you promote a secondary cluster, perform the following steps to verify that the secondary cluster has applied all transactions received from the primary cluster:

1. Stop all writes to the primary cluster.

2. Check the replication status of the secondary cluster by completing the following steps:

   1. In the Google Cloud console, go to the Clusters page.

      Go to Clusters

   2. In the list of clusters, click the name of the secondary cluster that you want to promote.

   3. On the cluster detail page, click Monitoring.

   4. In the Monitoring list, select the secondary instance. It appears in the list as Secondary: INSTANCE_NAME.

   5. In the list of metrics, locate the Replication lag from primary instance chart.

   6. Confirm that the chart shows minimal lag.

      A lag value of 0 is ideal. If the lag is greater than 0, then you can still promote the secondary cluster, at the risk of losing some recent transactions already committed at the primary cluster.

   7. In the list of metrics, locate the Replication status chart.

   8. Confirm that all nodes represented in the chart have a value of streaming.

Note: Backups are disabled on secondary clusters. If you want periodic backups after you promote a secondary cluster, you must configure automated backups and continuous backup and recovery After promotion, it might take up to 24 hours for continuous backup and recovery to take a backup and enable its capability. If you want to accelerate the backup operation, you can take an on-demand backup after promotion.

To promote a secondary cluster to primary cluster, follow these steps:

Console

1. In the Google Cloud console, go to the Clusters page.

   Go to Clusters

2. In the Resource Name column, click a secondary cluster that you want to promote as the primary cluster.

3. In the Overview page, click Promote cluster.

4. In the dialog that appears, enter your secondary cluster ID to confirm that you want to promote the cluster.

5. Click Promote.

   After the cluster is promoted, the Type: Secondary cluster (highly available) field on the Overview page is updated to Type: Highly available with read pools.

gcloud

Use the gcloud alloydb clusters promote command:

 gcloud alloydb clusters promote SECONDARY_CLUSTER_ID \
 --region=REGION_ID \
 --project=PROJECT_ID \

Replace the following:

• SECONDARY_CLUSTER_ID: The ID of the secondary cluster that you want to promote.
• REGION_ID: The ID of the secondary cluster's region—for example,us-central1.
• PROJECT_ID: The ID of the secondary cluster's project.

What's Next

• View cluster details.
• View the list of clusters.