Quickstart: Create a multi-region cluster with Azure Managed Instance for Apache Cassandra

Article
08/14/2024

Azure Managed Instance for Apache Cassandra is a fully managed service for pure open-source Apache Cassandra clusters. The service also allows configurations to be overridden, depending on the specific needs of each workload, allowing maximum flexibility and control where needed.

This quickstart demonstrates how to use the Azure CLI commands to configure a multi-region cluster in Azure.

Prerequisites

Use the Bash environment in Azure Cloud Shell. For more information, see Quickstart for Bash in Azure Cloud Shell.
If you prefer to run CLI reference commands locally, install the Azure CLI. If you're running on Windows or macOS, consider running Azure CLI in a Docker container. For more information, see How to run the Azure CLI in a Docker container.
- If you're using a local installation, sign in to the Azure CLI by using the az login command. To finish the authentication process, follow the steps displayed in your terminal. For other sign-in options, see Sign in with the Azure CLI.
- When you're prompted, install the Azure CLI extension on first use. For more information about extensions, see Use extensions with the Azure CLI.
- Run az version to find the version and dependent libraries that are installed. To upgrade to the latest version, run az upgrade.

This article requires the Azure CLI version 2.30.0 or higher. If you're using Azure Cloud Shell, the latest version is already installed.
Azure Virtual Network with connectivity to your self-hosted or on-premises environment. For more information on connecting on premises environments to Azure, see the Connect an on-premises network to Azure article.

Set up the network environment

Because all datacenters provisioned with this service must be deployed into dedicated subnets using VNet injection, configure appropriate network peering in advance of deployment. For this quickstart, create a cluster with two datacenters in separate regions: East US and East US 2. First, create the virtual networks for each region.

Create a resource group named cassandra-mi-multi-region:

az group create --location eastus2 --name cassandra-mi-multi-region

Create the first VNet in East US 2 with a dedicated subnet:

az network vnet create \
  --name vnetEastUs2 \
  --location eastus2 \
  --resource-group cassandra-mi-multi-region \
  --address-prefix 10.0.0.0/16 \
  --subnet-name dedicated-subnet

Create the second VNet in East US, also with a dedicated subnet:

 az network vnet create \
   --name vnetEastUs \
   --location eastus \
   --resource-group cassandra-mi-multi-region \
   --address-prefix 192.168.0.0/16 \
   --subnet-name dedicated-subnet

Note

We explicitly add different IP address ranges to ensure no errors when peering.

Peer the first VNet to the second VNet:

az network vnet peering create \
  --resource-group cassandra-mi-multi-region \
  --name MyVnet1ToMyVnet2 \
  --vnet-name vnetEastUs2 \
  --remote-vnet vnetEastUs \
  --allow-vnet-access \
  --allow-forwarded-traffic

In order to connect the two VNets, create another peering between the second VNet and the first:

az network vnet peering create \
  --resource-group cassandra-mi-multi-region \
  --name MyVnet2ToMyVnet1 \
  --vnet-name vnetEastUs \
  --remote-vnet vnetEastUs2 \
  --allow-vnet-access \
  --allow-forwarded-traffic

Note

If you add more regions, each VNet requires peering from it to all other VNets, and from all other VNets to it.

Check the output of the previous command. Make sure the value of "peeringState" is now "Connected". You can also check this result by running the following command:
```
az network vnet peering show \
  --name MyVnet1ToMyVnet2 \
  --resource-group cassandra-mi-multi-region \
  --vnet-name vnetEastUs2 \
  --query peeringState
```

Apply some special permissions to both Virtual Networks. Azure Managed Instance for Apache Cassandra requires these permissions. Run the following command. Replace <SubscriptionID> with your subscription ID:

az role assignment create \
  --assignee a232010e-820c-4083-83bb-3ace5fc29d0b \
  --role 4d97b98b-1d4f-4787-a291-c67834d212e7 \
  --scope /subscriptions/<SubscriptionID>/resourceGroups/cassandra-mi-multi-region/providers/Microsoft.Network/virtualNetworks/vnetEastUs2

az role assignment create     \
  --assignee a232010e-820c-4083-83bb-3ace5fc29d0b \
  --role 4d97b98b-1d4f-4787-a291-c67834d212e7 \
  --scope /subscriptions/<SubscriptionID>/resourceGroups/cassandra-mi-multi-region/providers/Microsoft.Network/virtualNetworks/vnetEastUs

Note

The assignee and role values in the previous command are fixed values. Enter these values exactly as in the command.

If you encounter errors when you run az role assignment create, you might not have permissions to run it. Check with your administrator for permissions.

Create a multi-region cluster

Deploy the cluster resource. Replace <Subscription ID> with your subscription ID. The deployment can take five to 10 minutes:

resourceGroupName='cassandra-mi-multi-region'
clusterName='test-multi-region'
location='eastus2'
delegatedManagementSubnetId='/subscriptions/<SubscriptionID>/resourceGroups/cassandra-mi-multi-region/providers/Microsoft.Network/virtualNetworks/vnetEastUs2/subnets/dedicated-subnet'
initialCassandraAdminPassword='myPassword'

 az managed-cassandra cluster create \
   --cluster-name $clusterName \
   --resource-group $resourceGroupName \
   --location $location \
   --delegated-management-subnet-id $delegatedManagementSubnetId \
   --initial-cassandra-admin-password $initialCassandraAdminPassword \
   --debug

After the cluster resource is created, you're ready to create a data center. First, create a datacenter in East US 2. Replace <SubscriptionID> with your subscription ID. This action can take up to 10 minutes:

resourceGroupName='cassandra-mi-multi-region'
clusterName='test-multi-region'
dataCenterName='dc-eastus2'
dataCenterLocation='eastus2'
delegatedManagementSubnetId='/subscriptions/<SubscriptionID>/resourceGroups/cassandra-mi-multi-region/providers/Microsoft.Network/virtualNetworks/vnetEastUs2/subnets/dedicated-subnet'

 az managed-cassandra datacenter create \
    --resource-group $resourceGroupName \
    --cluster-name $clusterName \
    --data-center-name $dataCenterName \
    --data-center-location $dataCenterLocation \
    --delegated-subnet-id $delegatedManagementSubnetId \
    --node-count 3

Create a datacenter in East US. Replace <SubscriptionID> with your subscription ID.
```
resourceGroupName='cassandra-mi-multi-region'
clusterName='test-multi-region'
dataCenterName='dc-eastus'
dataCenterLocation='eastus'
delegatedManagementSubnetId='/subscriptions/<SubscriptionID>/resourceGroups/cassandra-mi-multi-region/providers/Microsoft.Network/virtualNetworks/vnetEastUs/subnets/dedicated-subnet'
virtualMachineSKU='Standard_D8s_v4'
noOfDisksPerNode=4

 az managed-cassandra datacenter create \
   --resource-group $resourceGroupName \
   --cluster-name $clusterName \
   --data-center-name $dataCenterName \
   --data-center-location $dataCenterLocation \
   --delegated-subnet-id $delegatedManagementSubnetId \
   --node-count 3
   --sku $virtualMachineSKU \
   --disk-capacity $noOfDisksPerNode \
   --availability-zone false
```
Note

The value for --sku can be chosen from the following available SKUs:
- Standard_E8s_v4
- Standard_E16s_v4
- Standard_E20s_v4
- Standard_E32s_v4
- Standard_DS13_v2
- Standard_DS14_v2
- Standard_D8s_v4
- Standard_D16s_v4
- Standard_D32s_v4
Note also that --availability-zone is set to false. To enable availability zones, set this to true. Availability zones increase the availability SLA of the service. For more information, see SLA for Azure Managed Instance for Apache Cassandra.
Warning

Availability zones are not supported in all regions. Deployments fail if you select a region where Availability zones are not supported. For supported regions, see Azure regions with availability zones.

The successful deployment of availability zones is also subject to the availability of compute resources in all of the zones in the given region. Deployments may fail if the SKU you have selected, or capacity, is not available across all zones.

Once the second datacenter is created, get the node status to verify that all the Cassandra nodes came up successfully:

resourceGroupName='cassandra-mi-multi-region'
clusterName='test-multi-region'

az managed-cassandra cluster status\
   --cluster-name $clusterName \
   --resource-group $resourceGroupName

Then connect to your cluster using CQLSH, and use the following CQL query to update the replication strategy in each keyspace to include all datacenters across the cluster (system tables will be updated automatically):
```
ALTER KEYSPACE "ks" WITH REPLICATION = {'class': 'NetworkTopologyStrategy', 'dc-eastus2': 3, 'dc-eastus': 3};
```
Finally, if you are adding a data center to a cluster where there is already data, you will need to run rebuild in order to replicate the historical data. In this case, we'll assume that the dc-eastus2 data center already has data. In Azure CLI, run the below command to execute nodetool rebuild on each node in your new dc-eastus data center, replacing <ip address> with the IP address of the node:
```
az managed-cassandra cluster invoke-command \
  --resource-group $resourceGroupName \
  --cluster-name $clusterName \
  --host <ip address> \
  --command-name nodetool --arguments rebuild="" "dc-eastus2"=""
```
Warning

You should not allow application clients to write to the new data center until you have applied keyspace replication changes. Otherwise, rebuild won't work, and you will need to create a support request so our team can run repair on your behalf.

Troubleshooting

If you encounter an error when applying permissions to your Virtual Network using Azure CLI, you can apply the same permission manually from the Azure portal. An example error might be Cannot find user or service principal in graph database for 'e5007d2c-4b13-4a74-9b6a-605d99f03501'. For more information, see Use Azure portal to add an Azure Cosmos DB service principal.

Note

The Azure Cosmos DB role assignment is used for deployment purposes only. Azure Managed Instanced for Apache Cassandra has no backend dependencies on Azure Cosmos DB.

Clean up resources

If you're not going to continue to use this managed instance cluster, delete it with the following steps:

From the left-hand menu of Azure portal, select Resource groups.
From the list, select the resource group you created for this quickstart.
On the resource group Overview pane, select Delete resource group.
In the next window, enter the name of the resource group to delete, and then select Delete.

Next steps

In this quickstart, you learned how to create a multi-region cluster using Azure CLI and Azure Managed Instance for Apache Cassandra. You can now start working with the cluster.

Manage Azure Managed Instance for Apache Cassandra resources using Azure CLI

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Quickstart: Create a multi-region cluster with Azure Managed Instance for Apache Cassandra

Prerequisites

Set up the network environment

Create a multi-region cluster

Troubleshooting

Clean up resources

Next steps

Feedback

Additional resources