Migrating Redis cluster hosts to a different availability zone

Managed Service for Redis cluster hosts reside in availability zones Yandex Cloud. To move hosts from one zone to another, add hosts residing in the target availability zone to the cluster and delete the hosts in the source availability zone:

1. Create a subnet in the availability zone you want to move your hosts to.

2. If your cluster uses the b2.medium or b3-c1-m4 host class, change it. Otherwise, you will not be able to add hosts to the cluster and perform migration.

   The cluster is unavailable for about five to seven minutes after changing the host class.

   You can restore the original class after migration.

3. Add a host to your cluster:

   Management console

   CLI

   Terraform

   API

   1. Go to the folder page and select Managed Service for Redis.

   2. Click the cluster name and go to the Hosts tab.

   3. Click Create host.

   4. Specify the host parameters:

      • Availability zone to which you want to move the hosts.
      • New subnet.
      • Select Public access if the host must be accessible from outside Yandex Cloud.

   5. Click Save.

   If you do not have the Yandex Cloud command line interface yet, install and initialize it.

   The folder specified in the CLI profile is used by default. You can specify a different folder using the --folder-name or --folder-id parameter.

   Run this command:

   yc managed-redis host add \
      --cluster-name <cluster_name> \
      --host zone-id=<availability_zone>,`
            `subnet-id=<new_subnet_ID>,`
            `assign-public-ip=<host_public_access:_true_or_false>
   

   You can retrieve the cluster name with a list of clusters in the folder.

   In the zone-id parameter, specify the availability zone you are moving the hosts to.

   1. Add a host manifest to the Terraform configuration file with the infrastructure plan:

      resource "yandex_mdb_redis_cluster" "<cluster_name>" {
        ...
        host {
          zone             = "<availability_zone>"
          subnet_id        = "<new_subnet_ID>"
          assign_public_ip = <host_public_access:_true_or_false>
        }
      }
      

      In the zone parameter, specify the availability zone you are moving the hosts to.

   2. Make sure the settings are correct.

      1. Using the command line, navigate to the folder that contains the up-to-date Terraform configuration files with an infrastructure plan.

      2. Run the command:

         terraform validate
         

         If there are errors in the configuration files, Terraform will point to them.

   3. Confirm updating the resources.

      1. Run the command to view planned changes:

         terraform plan
         

         If the resource configuration descriptions are correct, the terminal will display a list of the resources to modify and their parameters. This is a test step. No resources are updated.

      2. If you are happy with the planned changes, apply them:

         1. Run the command:

            terraform apply
            

         2. Confirm the update of resources.

         3. Wait for the operation to complete.

   To add a host to a cluster, use the addHosts REST API method for the Cluster resource or the ClusterService/AddHosts gRPC API call and provide the following in the request:

   • Cluster ID in the clusterId parameter. You can get the ID with a list of clusters in the folder.
   • New host settings in the hostSpecs parameters.

4. To successfully connect to the database after the migration is complete, specify the new host's FQDN in your backend or client (for example, in the code or graphical IDE). Delete the original host's FQDN in the source availability zone.

   To find out the FQDN, get a list of hosts in the cluster:

   yc managed-redis host list --cluster-name <cluster_name>
   

   The FQDN is specified in the command output under NAME.

5. Delete the hosts in the source availability zone:

   Management console

   CLI

   Terraform

   API

   1. Go to the folder page and select Managed Service for Redis.
   2. Click the cluster name and open the Hosts tab.
   3. Click in the host's row, select Delete, and confirm the deletion.

   Run the following command for each host:

   yc managed-redis host delete <host_FQDN> --cluster-name <cluster_name>
   

   1. In the Terraform configuration file with the infrastructure plan, remove the host sections with the source availability zone from the cluster description.

   2. Make sure the settings are correct.

      1. Using the command line, navigate to the folder that contains the up-to-date Terraform configuration files with an infrastructure plan.

      2. Run the command:

         terraform validate
         

         If there are errors in the configuration files, Terraform will point to them.

   3. Type yes and press Enter.

      1. Run the command to view planned changes:

         terraform plan
         

         If the resource configuration descriptions are correct, the terminal will display a list of the resources to modify and their parameters. This is a test step. No resources are updated.

      2. If you are happy with the planned changes, apply them:

         1. Run the command:

            terraform apply
            

         2. Confirm the update of resources.

         3. Wait for the operation to complete.

   To delete a host, use the deleteHosts REST API method for the Cluster resource or the ClusterService/DeleteHosts gRPC API call and provide the following in the request:

   • Cluster ID in the clusterId parameter. To find out the cluster ID, get a list of clusters in the folder.
   • FQDN or an array of names of the hosts you want to delete, in the hostNames parameter.

6. Wait until the cluster status changes to Alive. In the management console, go to the folder page and select Managed Service for Redis. You can see the cluster status in the Availability column.