Changing the number of replicas - Amazon MemoryDB
Increasing the Number of ReplicasDecreasing the Number of Replicas

Changing the number of replicas

You can dynamically increase or decrease the number of read replicas in your MemoryDB cluster using the AWS Management Console, the AWS CLI, or the MemoryDB API. All shards must have the same number of replicas.

Increasing the number of replicas in a cluster

You can increase the number of replicas in a MemoryDB cluster up to a maximum of five per shard. You can do so using the AWS Management Console, the AWS CLI, or the MemoryDB API.

Using the AWS Management Console

To increase the number of replicas in a MemoryDB cluster (console), see Adding / Removing nodes from a cluster.

Using the AWS CLI

To increase the number of replicas in a MemoryDB cluster, use the update-cluster command with the following parameters:

  • --cluster-name – Required. Identifies which cluster you want to increase the number of replicas in.

  • --replica-configuration – Required. Allows you to set the number of replicas. To increase the replica count, set the ReplicaCount property to the number of replicas that you want in this shard at the end of this operation.

The following example increases the number of replicas in the cluster my-cluster to 2.

For Linux, macOS, or Unix:

aws memorydb update-cluster \
    --cluster-name my-cluster \
    --replica-configuration \
        ReplicaCount=2

For Windows:

aws memorydb update-cluster ^
    --cluster-name my-cluster ^
    --replica-configuration ^
        ReplicaCount=2

It returns the following JSON response:

{
    "Cluster": {
        "Name": "my-cluster",
        "Status": "updating",
        "NumberOfShards": 1,
        "ClusterEndpoint": {
            "Address": "clustercfg.my-cluster.xxxxx.memorydb.us-east-1.amazonaws.com",
            "Port": 6379
        },
        "NodeType": "db.r6g.large",
        "EngineVersion": "6.2",
        "EnginePatchVersion": "6.2.6",
        "ParameterGroupName": "default.memorydb-redis6",
        "ParameterGroupStatus": "in-sync",
        "SubnetGroupName": "my-sg",
        "TLSEnabled": true,
        "ARN": "arn:aws:memorydb:us-east-1:xxxxxxexamplearn:cluster/my-cluster",
        "SnapshotRetentionLimit": 0,
        "MaintenanceWindow": "wed:03:00-wed:04:00",
        "SnapshotWindow": "04:30-05:30",
        "DataTiering": "false",
        "AutoMinorVersionUpgrade": true
    }
}

To view the details of the updated cluster once its status changes from updating to available, use the following command:

For Linux, macOS, or Unix:

aws memorydb describe-clusters \
    --cluster-name my-cluster
    --show-shard-details

For Windows:

aws memorydb describe-clusters ^
    --cluster-name my-cluster
    --show-shard-details

It will return the following JSON response:

{
    "Clusters": [
        {
            "Name": "my-cluster",
            "Status": "available",
            "NumberOfShards": 1,
            "Shards": [
                {
                    "Name": "0001",
                    "Status": "available",
                    "Slots": "0-16383",
                    "Nodes": [
                        {
                            "Name": "my-cluster-0001-001",
                            "Status": "available",
                            "AvailabilityZone": "us-east-1a",
                            "CreateTime": "2021-08-21T20:22:12.405000-07:00",
                            "Endpoint": {
                                "Address": "clustercfg.my-cluster.xxxxxx.memorydb.us-east-1.amazonaws.com",
                                "Port": 6379
                            }
                        },
                        {
                            "Name": "my-cluster-0001-002",
                            "Status": "available",
                            "AvailabilityZone": "us-east-1b",
                            "CreateTime": "2021-08-21T20:22:12.405000-07:00",
                            "Endpoint": {
                                "Address": "clustercfg.my-cluster.xxxxxx.memorydb.us-east-1.amazonaws.com",
                                "Port": 6379
                            }
                        },
                        {
                            "Name": "my-cluster-0001-003",
                            "Status": "available",
                            "AvailabilityZone": "us-east-1a",
                            "CreateTime": "2021-08-22T12:59:31.844000-07:00",
                            "Endpoint": {
                                "Address": "clustercfg.my-cluster.xxxxxx.memorydb.us-east-1.amazonaws.com",
                                "Port": 6379
                            }
                        }
                    ],
                    "NumberOfNodes": 3
                }
            ],
            "ClusterEndpoint": {
                "Address": "clustercfg.my-cluster.xxxxxx.memorydb.us-east-1.amazonaws.com",
                "Port": 6379
            },
            "NodeType": "db.r6g.large",
            "EngineVersion": "6.2",
            "EnginePatchVersion": "6.2.6",
            "ParameterGroupName": "default.memorydb-redis6",
            "ParameterGroupStatus": "in-sync",
            "SubnetGroupName": "my-sg",
            "TLSEnabled": true,
            "ARN": "arn:aws:memorydb:us-east-1:xxxxxxexamplearn:cluster/my-cluster",
            "SnapshotRetentionLimit": 0,
            "MaintenanceWindow": "wed:03:00-wed:04:00",
            "SnapshotWindow": "04:30-05:30",
            "ACLName": "my-acl",
            "DataTiering": "false",
            "AutoMinorVersionUpgrade": true
        }
    ]
}

For more information about increasing the number of replicas using the CLI, see update-cluster in the AWS CLI Command Reference.

Using the MemoryDB API

To increase the number of replicas in a MemoryDB shard, use the UpdateCluster action with the following parameters:

  • ClusterName – Required. Identifies which cluster you want to increase the number of replicas in.

  • ReplicaConfiguration – Required. Allows you to set the number of replicas. To increase the replica count, set the ReplicaCount property to the number of replicas that you want in this shard at the end of this operation.

The following example increases the number of replicas in the cluster sample-cluster to three. When the example is finished, there are three replicas in each shard. This number applies whether this is a MemoryDB cluster with a single shard or a MemoryDB cluster with multiple shards.

https://memory-db.us-east-1.amazonaws.com/
      ?Action=UpdateCluster      
      &ReplicaConfiguration.ReplicaCount=3
      &ClusterName=sample-cluster
      &Version=2021-01-01
      &SignatureVersion=4
      &SignatureMethod=HmacSHA256
      &Timestamp=20210802T192317Z
      &X-Amz-Credential=<credential>

For more information about increasing the number of replicas using the API, see UpdateCluster.

Decreasing the number of replicas in a cluster

You can decrease the number of replicas in a cluster for MemoryDB. You can decrease the number of replicas to zero, but you can't failover to a replica if your primary node fails.

You can use the AWS Management Console, the AWS CLI or the MemoryDB API to decrease the number of replicas in a cluster.

Using the AWS Management Console

To decrease the number of replicas in a MemoryDB cluster (console), see Adding / Removing nodes from a cluster.

Using the AWS CLI

To decrease the number of replicas in a MemoryDB cluster, use the update-cluster command with the following parameters:

  • --cluster-name – Required. Identifies which cluster you want to decrease the number of replicas in.

  • --replica-configuration – Required.

    ReplicaCount – Set this property to specify the number of replica nodes you want.

The following example uses --replica-configuration to decrease the number of replicas in the cluster my-cluster to the value specified.

For Linux, macOS, or Unix:

aws memorydb update-cluster \
    --cluster-name my-cluster \
    --replica-configuration \
        ReplicaCount=1

For Windows:

aws memorydb update-cluster ^
    --cluster-name my-cluster ^
    --replica-configuration ^
        ReplicaCount=1 ^

It will return the following JSON response:

{
    "Cluster": {
        "Name": "my-cluster",
        "Status": "updating",
        "NumberOfShards": 1,
        "ClusterEndpoint": {
            "Address": "clustercfg.my-cluster.xxxxxx.memorydb.us-east-1.amazonaws.com",
            "Port": 6379
        },
        "NodeType": "db.r6g.large",
        "EngineVersion": "6.2",
        "EnginePatchVersion": "6.2.6",
        "ParameterGroupName": "default.memorydb-redis6",
        "ParameterGroupStatus": "in-sync",
        "SubnetGroupName": "my-sg",
        "TLSEnabled": true,
        "ARN": "arn:aws:memorydb:us-east-1:xxxxxxexamplearn:cluster/my-cluster",
        "SnapshotRetentionLimit": 0,
        "MaintenanceWindow": "wed:03:00-wed:04:00",
        "SnapshotWindow": "04:30-05:30",
        "DataTiering": "false",
        "AutoMinorVersionUpgrade": true
    }
}

To view the details of the updated cluster once its status changes from updating to available, use the following command:

For Linux, macOS, or Unix:

aws memorydb describe-clusters \
    --cluster-name my-cluster
    --show-shard-details

For Windows:

aws memorydb describe-clusters ^
    --cluster-name my-cluster
    --show-shard-details

It will return the following JSON response:

{
    "Clusters": [
        {
            "Name": "my-cluster",
            "Status": "available",
            "NumberOfShards": 1,
            "Shards": [
                {
                    "Name": "0001",
                    "Status": "available",
                    "Slots": "0-16383",
                    "Nodes": [
                        {
                            "Name": "my-cluster-0001-001",
                            "Status": "available",
                            "AvailabilityZone": "us-east-1a",
                            "CreateTime": "2021-08-21T20:22:12.405000-07:00",
                            "Endpoint": {
                                "Address": "clustercfg.my-cluster.xxxxxx.memorydb.us-east-1.amazonaws.com",
                                "Port": 6379
                            }
                        },
                        {
                            "Name": "my-cluster-0001-002",
                            "Status": "available",
                            "AvailabilityZone": "us-east-1b",
                            "CreateTime": "2021-08-21T20:22:12.405000-07:00",
                            "Endpoint": {
                                "Address": "clustercfg.my-cluster.xxxxxx.memorydb.us-east-1.amazonaws.com",
                                "Port": 6379
                            }
                        }
                    ],
                    "NumberOfNodes": 2
                }
            ],
            "ClusterEndpoint": {
                "Address": "clustercfg.my-cluster.xxxxxx.memorydb.us-east-1.amazonaws.com",
                "Port": 6379
            },
            "NodeType": "db.r6g.large",
            "EngineVersion": "6.2",
            "EnginePatchVersion": "6.2.6",
            "ParameterGroupName": "default.memorydb-redis6",
            "ParameterGroupStatus": "in-sync",
            "SubnetGroupName": "my-sg",
            "TLSEnabled": true,
            "ARN": "arn:aws:memorydb:us-east-1:xxxxxxexamplearn:cluster/my-cluster",
            "SnapshotRetentionLimit": 0,
            "MaintenanceWindow": "wed:03:00-wed:04:00",
            "SnapshotWindow": "04:30-05:30",
            "ACLName": "my-acl",
            "DataTiering": "false",
            "AutoMinorVersionUpgrade": true
        }
    ]
}

For more information about decreasing the number of replicas using the CLI, see update-cluster in the AWS CLI Command Reference.

Using the MemoryDB API

To decrease the number of replicas in a MemoryDB cluster, use the UpdateCluster action with the following parameters:

  • ClusterName – Required. Identifies which cluster you want to decrease the number of replicas in.

  • ReplicaConfiguration – Required. Allows you to set the number of replicas.

    ReplicaCount – Set this property to specify the number of replica nodes you want.

The following example uses ReplicaCount to decrease the number of replicas in the cluster sample-cluster to one. When the example is finished, there is one replica in each shard. This number applies whether this is a MemoryDB cluster with a single shard or a MemoryDB cluster with multiple shards.

https://memory-db.us-east-1.amazonaws.com/
      ?Action=UpdateCluster    
      &ReplicaConfiguration.ReplicaCount=1
      &ClusterName=sample-cluster
      &Version=2021-01-01
      &SignatureVersion=4
      &SignatureMethod=HmacSHA256
      &Timestamp=20210802T192317Z
      &X-Amz-Credential=<credential>

For more information about decreasing the number of replicas using the API, see UpdateCluster.