Online resharding and shard rebalancing for MemoryDB - Amazon MemoryDB for Redis
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Online resharding and shard rebalancing for MemoryDB

By using online resharding and shard rebalancing with MemoryDB, you can scale your MemoryDB dynamically with no downtime. This approach means that your cluster can continue to serve requests even while scaling or rebalancing is in process.

You can do the following:

  • Scale out – Increase read and write capacity by adding shards to your MemoryDB cluster.

    If you add one or more shards to your cluster, the number of nodes in each new shard is the same as the number of nodes in the smallest of the existing shards.

  • Scale in – Reduce read and write capacity, and thereby costs, by removing shards from your MemoryDB cluster.

Currently, the following limitations apply to MemoryDB online resharding:

  • There are limitations with slots or keyspaces and large items:

    If any of the keys in a shard contain a large item, that key isn't migrated to a new shard when scaling out or rebalancing. This functionality can result in unbalanced shards.

    If any of the keys in a shard contain a large item (items greater than 256 MB after serialization), that shard isn't deleted when scaling in. This functionality can result in some shards not being deleted.

  • When scaling out, the number of nodes in any new shards equals the number of nodes in the existing shards.

For more information, see Best practices: Online cluster resizing.

You can horizontally scale or rebalance your MemoryDB clusters using the Amazon Web Services Management Console, the Amazon CLI, and the MemoryDB API.

Adding shards with online resharding

You can add shards to your MemoryDB cluster using the Amazon Web Services Management Console, Amazon CLI, or MemoryDB API.

You can use the Amazon Web Services Management Console to add one or more shards to your MemoryDB cluster. The following procedure describes the process.

  1. Sign in to the Amazon Web Services Management Console and open the MemoryDB for Redis console at https://console.amazonaws.cn/memorydb/.

  2. From the list of clusters, choose the cluster name from which you want to add a shard.

  3. Under the Shards and nodes tab, choose Add/Delete shards

  4. In New number of shards, enter the the number of shards you want.

  5. Choose Confirm to keep the changes or Cancel to discard.

The following process describes how to reconfigure the shards in your MemoryDB cluster by adding shards using the Amazon CLI.

Use the following parameters with update-cluster.

Parameters

  • --cluster-name – Required. Specifies which cluster (cluster) the shard reconfiguration operation is to be performed on.

  • --shard-configuration – Required. Allows you to set the number of shards.

    • ShardCount – Set this property to specify the number of shards you want.

The following example modifies the number of shards in the cluster my-cluster to 2.

For Linux, OS X, or Unix:

aws memorydb update-cluster \ --cluster-name my-cluster \ --shard-configuration \ ShardCount=2

For Windows:

aws memorydb update-cluster ^ --cluster-name my-cluster ^ --shard-configuration ^ ShardCount=2

It returns the following JSON response:

{ "Cluster": { "Name": "my-cluster", "Status": "updating", "NumberOfShards": 2, "AvailabilityMode": "MultiAZ", "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, OS X, 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": 2, "Shards": [ { "Name": "0001", "Status": "available", "Slots": "0-8191", "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 }, { "Name": "0002", "Status": "available", "Slots": "8192-16383", "Nodes": [ { "Name": "my-cluster-0002-001", "Status": "available", "AvailabilityZone": "us-east-1b", "CreateTime": "2021-08-22T14:26:18.693000-07:00", "Endpoint": { "Address": "clustercfg.my-cluster.xxxxxx.memorydb.us-east-1.amazonaws.com", "Port": 6379 } }, { "Name": "my-cluster-0002-002", "Status": "available", "AvailabilityZone": "us-east-1a", "CreateTime": "2021-08-22T14:26:18.765000-07:00", "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, see update-cluster in the Amazon CLI Command Reference.

You can use the MemoryDB API to reconfigure the shards in your MemoryDB cluster online by using the UpdateCluster operation.

Use the following parameters with UpdateCluster.

Parameters

  • ClusterName – Required. Specifies which cluster the shard reconfiguration operation is to be performed on.

  • ShardConfiguration – Required. Allows you to set the number of shards.

    • ShardCount – Set this property to specify the number of shards you want.

For more information, see UpdateCluster.

Removing shards with online resharding

You can remove shards from your MemoryDB cluster using the Amazon Web Services Management Console, Amazon CLI, or MemoryDB API.

The following process describes how to reconfigure the shards in your MemoryDB cluster by removing shards using the Amazon Web Services Management Console.

Important

Before removing shards from your cluster, MemoryDB makes sure that all your data will fit in the remaining shards. If the data will fit, shards are deleted from the cluster as requested. If the data won't fit in the remaining shards, the process is terminated and the cluster is left with the same shard configuration as before the request was made.

You can use the Amazon Web Services Management Console to remove one or more shards from your MemoryDB cluster. You cannot remove all the shards in a cluster. Instead, you must delete the cluster. For more information, see Step 4: Deleting a cluster. The following procedure describes the process for removing one or more shards.

  1. Sign in to the Amazon Web Services Management Console and open the MemoryDB for Redis console at https://console.amazonaws.cn/memorydb/.

  2. From the list of clusters, choose the cluster name from which you want to remove a shard.

  3. Under the Shards and nodes tab, choose Add/Delete shards

  4. In New number of shards, enter the the number of shards you want (with a minimum of 1).

  5. Choose Confirm to keep the changes or Cancel to discard.

The following process describes how to reconfigure the shards in your MemoryDB cluster by removing shards using the Amazon CLI.

Important

Before removing shards from your cluster, MemoryDB makes sure that all your data will fit in the remaining shards. If the data will fit, shards are deleted from the cluster as requested and their keyspaces mapped into the remaining shards. If the data will not fit in the remaining shards, the process is terminated and the cluster is left with the same shard configuration as before the request was made.

You can use the Amazon CLI to remove one or more shards from your MemoryDB cluster. You cannot remove all the shards in a cluster. Instead, you must delete the cluster. For more information, see Step 4: Deleting a cluster.

Use the following parameters with update-cluster.

Parameters

  • --cluster-name – Required. Specifies which cluster (cluster) the shard reconfiguration operation is to be performed on.

  • --shard-configuration – Required. Allows you to set the number of shards using the ShardCount property:

    ShardCount – Set this property to specify the number of shards you want.

The following example modifies the number of shards in the cluster my-cluster to 2.

For Linux, OS X, or Unix:

aws memorydb update-cluster \ --cluster-name my-cluster \ --shard-configuration \ ShardCount=2

For Windows:

aws memorydb update-cluster ^ --cluster-name my-cluster ^ --shard-configuration ^ ShardCount=2

It returns the following JSON response:

{ "Cluster": { "Name": "my-cluster", "Status": "updating", "NumberOfShards": 2, "AvailabilityMode": "MultiAZ", "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, OS X, 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": 2, "Shards": [ { "Name": "0001", "Status": "available", "Slots": "0-8191", "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 }, { "Name": "0002", "Status": "available", "Slots": "8192-16383", "Nodes": [ { "Name": "my-cluster-0002-001", "Status": "available", "AvailabilityZone": "us-east-1b", "CreateTime": "2021-08-22T14:26:18.693000-07:00", "Endpoint": { "Address": "clustercfg.my-cluster.xxxxxx.memorydb.us-east-1.amazonaws.com", "Port": 6379 } }, { "Name": "my-cluster-0002-002", "Status": "available", "AvailabilityZone": "us-east-1a", "CreateTime": "2021-08-22T14:26:18.765000-07:00", "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, see update-cluster in the Amazon CLI Command Reference.

You can use the MemoryDB API to reconfigure the shards in your MemoryDB cluster online by using the UpdateCluster operation.

The following process describes how to reconfigure the shards in your MemoryDB cluster by removing shards using the MemoryDB API.

Important

Before removing shards rom your cluster, MemoryDB makes sure that all your data will fit in the remaining shards. If the data will fit, shards are deleted from the cluster as requested and their keyspaces mapped into the remaining shards. If the data will not fit in the remaining shards, the process is terminated and the cluster is left with the same shard configuration as before the request was made.

You can use the MemoryDB API to remove one or more shards from your MemoryDB cluster. You cannot remove all the shards in a cluster. Instead, you must delete the cluster. For more information, see Step 4: Deleting a cluster.

Use the following parameters with UpdateCluster.

Parameters

  • ClusterName – Required. Specifies which cluster (cluster) the shard reconfiguration operation is to be performed on.

  • ShardConfiguration – Required. Allows you to set the number of shards using the ShardCount property:

    ShardCount – Set this property to specify the number of shards you want.