Creating a Redis (cluster mode enabled) Replication Group from Scratch

You can create a Redis (cluster mode enabled) cluster (API/CLI: replication group) using the ElastiCache console, the AWS CLI, or the ElastiCache API. A Redis (cluster mode enabled) replication group has from 1 to 15 shards (API/CLI: node groups), a primary cluster in each shard, and up to 5 read replicas in each shard. When you use the ElastiCache console to create the cluster, the number of read replicas is the same for every shard.

Creating a Redis (cluster mode enabled) Cluster

Using the ElastiCache Console
Creating a Redis (cluster mode enabled) Replication Group from Scratch (AWS CLI)
Creating a Redis (cluster mode enabled) Replication Group from Scratch (ElastiCache API)

Creating a Redis (cluster mode enabled) Cluster (Console)

To create a Redis (cluster mode enabled) cluster, see Creating a Redis (cluster mode enabled) Cluster (Console). Be sure to enable cluster mode, Cluster Mode enabled (Scale Out), and specify at least two shards and one replica node.

Creating a Redis (cluster mode enabled) Replication Group from Scratch (AWS CLI)

The following procedure creates a Redis (cluster mode enabled) replication group using the AWS CLI.

When you create a Redis (cluster mode enabled) replication group from scratch, you create the replication group and all its nodes with a single call to the AWS CLI create-replication-group command. Include the following parameters.

--replication-group-id

The name of the replication group you are creating.

Redis (cluster mode enabled) Replication Group naming constraints

Must contain from 1 to 20 alphanumeric characters or hyphens.
Must begin with a letter.
Cannot contain two consecutive hyphens.
Cannot end with a hyphen.

--replication-group-description

Description of the replication group.

--cache-node-type

The node type for each node in the replication group.

The following node types are supported by ElastiCache. Generally speaking, the current generation types provide more memory and computational power at lower cost when compared to their equivalent previous generation counterparts.

General purpose:
- Current generation:
  
  T2 node types: cache.t2.micro, cache.t2.small, cache.t2.medium
  
  M3 node types: cache.m3.medium, cache.m3.large, cache.m3.xlarge, cache.m3.2xlarge
  
  M4 node types: cache.m4.large, cache.m4.xlarge, cache.m4.2xlarge, cache.m4.4xlarge, cache.m4.10xlarge
- Previous generation: (not recommended)
  
  T1 node types: cache.t1.micro
  
  M1 node types: cache.m1.small, cache.m1.medium, cache.m1.large, cache.m1.xlarge
Compute optimized:
- Previous generation: (not recommended)
  
  C1 node types: cache.c1.xlarge
Memory optimized:
- Current generation:
  
  R3 node types: cache.r3.large, cache.r3.xlarge, cache.r3.2xlarge, cache.r3.4xlarge, cache.r3.8xlarge
  
  R4 node types: cache.r4.large, cache.r4.xlarge, cache.r4.2xlarge, cache.r4.4xlarge, cache.r4.8xlarge, cache.r4.16xlarge
- Previous generation: (not recommended)
  
  M2 node types: cache.m2.xlarge, cache.m2.2xlarge, cache.m2.4xlarge

Additional node type info

All T2 instances are created in an Amazon Virtual Private Cloud (Amazon VPC).
Redis backup and restore is not supported for T2 instances.
Redis append-only files (AOF) are not supported for T1 or T2 instances.
Redis Multi-AZ with automatic failover is not supported on T1 instances.
Redis Multi-AZ with automatic failover is supported on T2 instances only when running Redis (cluster mode enabled) - version 3.2.4 or later with the default.redis3.2.cluster.on parameter group or one derived from it.
Redis configuration variables appendonly and appendfsync are not supported on Redis version 2.8.22 and later.

--cache-parameter-group

Specify the default.redis3.2.cluster.on parameter group or a parameter group derived from default.redis3.2.cluster.on to create a Redis (cluster mode enabled) replication group. For more information, see Redis 3.2.4 Parameter Changes.

--engine

redis

--engine-version

3.2.4

--num-node-groups

The number of node groups in this replication group. Valid values are 1 to 15.

--replicas-per-node-group

The number of replica nodes in each node group. Valid values are 0 to 5.

If you want to enable in-transit or at-rest encryption on this replication group, add either or both of the --transit-encryption-enabled or --at-rest-encryption-enabled parameters and meet the following conditions.

Your replication group must be running Redis version 3.2.6 or 4.x.
The replication group must be created in a Amazon VPC
You must also include the parameter --cache-subnet-group.
You must also include the parameter --auth-token with the customer specified string value for your AUTH token (password) needed to perform operations on this replication group.

The following operation creates the Redis (cluster mode enabled) replication group new-group with three node groups/shards (--num-node-groups), each with three nodes, a primary and two read replicas (--replicas-per-node-group).

For Linux, macOS, or Unix:


aws elasticache create-replication-group \
   --replication-group-id new-group \
   --replication-group-description "Demo cluster with replicas" \
   --num-node-groups 3 \
   --replicas-per-node-group 2 \
   --cache-node-type cache.m4.large \
   --cache-parameter-group default.redis3.2.cluster.on \
   --engine redis \
   --engine-version 3.2.4

For Windows:


aws elasticache create-replication-group ^
   --replication-group-id new-group ^
   --replication-group-description "Demo cluster with replicas" ^
   --num-node-groups 3 ^
   --replicas-per-node-group 2 ^
   --cache-node-type cache.m4.large ^
   --cache-parameter-group default.redis3.2.cluster.on ^
   --engine redis ^
   --engine-version 3.2.4

The preceeding command generates the following output.


{
    "ReplicationGroup": {
        "Status": "creating", 
        "Description": "Demo cluster with replicas", 
        "ReplicationGroupId": "new-group", 
        "SnapshotRetentionLimit": 0, 
        "AutomaticFailover": "enabled", 
        "SnapshotWindow": "05:30-06:30", 
        "MemberClusters": [
            "new-group-0001-001", 
            "new-group-0001-002", 
            "new-group-0001-003", 
            "new-group-0002-001", 
            "new-group-0002-002", 
            "new-group-0002-003", 
            "new-group-0003-001", 
            "new-group-0003-002", 
            "new-group-0003-003"
        ], 
        "PendingModifiedValues": {}
    }
}

When you create a Redis (cluster mode enabled) replication group from scratch, you are able to configure each shard in the cluster using the --node-group-configuration parameter as shown in the following example which configures two node groups (Console: shards). The first shard has two nodes, a primary and one read replica. The second shard has three nodes, a primary and two read replicas.

--node-group-configuration

The configuration for each node group. The --node-group-configuration parameter consists of the following fields.

PrimaryAvailabilityZone – The Availability Zone where the primary node of this node group is located. If this parameter is omitted, ElastiCache chooses the Availability Zone for the primary node.

Example: us-west-2a.
ReplicaAvailabilityZones – A comma separated list of Availability Zones where the read replicas are located. The number of Availability Zones in this list must match the value of ReplicaCount. If this parameter is omitted, ElastiCache chooses the Availability Zones for the replica nodes.

Example: "us-west-2a,us-west-2b,us-west-2c"
ReplicaCount – The number of replica nodes in this node group.
Slots – A string that specifies the keyspace for the node group. The string is in the format startKey-endKey. If this parameter is omitted, ElastiCache allocates keys equally among the node groups.

Example: "0-4999"

The following operation creates the Redis (cluster mode enabled) replication group new-group with two node groups/shards (--num-node-groups). Unlike the preceeding example, each node group is configured differently from the other node node group (--node-group-configuration).

For Linux, macOS, or Unix:


aws elasticache create-replication-group \
  --replication-group-id rc-rg \
  --replication-group-description "Sharded replication group" \
  --engine redis \
  --engine-version 3.2.4 \
  --cache-parameter-group default.redis3.2.cluster.on \
  --snapshot-retention-limit 8 \
  --cache-node-type cache.m4.medium \
  --num-node-groups 2 \
  --node-group-configuration \
      "ReplicaCount=1,Slots=0-8999,PrimaryAvailabilityZone='us-east-1c',ReplicaAvailabilityZones='us-east-1b'" \
      "ReplicaCount=2,Slots=9000-16383,PrimaryAvailabilityZone='us-east-1a',ReplicaAvailabilityZones='us-east-1a','us-east-1c'"

For Windows:


aws elasticache create-replication-group ^
  --replication-group-id rc-rg ^
  --replication-group-description "Sharded replication group" ^
  --engine redis ^
  --engine-version 3.2.4 ^
  --cache-parameter-group default.redis3.2.cluster.on ^
  --snapshot-retention-limit 8 ^
  --cache-node-type cache.m4.medium ^
  --num-node-groups 2 ^
  --node-group-configuration \
      "ReplicaCount=1,Slots=0-8999,PrimaryAvailabilityZone='us-east-1c',ReplicaAvailabilityZones='us-east-1b'" \
      "ReplicaCount=2,Slots=9000-16383,PrimaryAvailabilityZone='us-east-1a',ReplicaAvailabilityZones='us-east-1a','us-east-1c'"

The preceeding operation generates the following output.


{
    "ReplicationGroup": {
        "Status": "creating", 
        "Description": "Sharded replication group", 
        "ReplicationGroupId": "rc-rg", 
        "SnapshotRetentionLimit": 8, 
        "AutomaticFailover": "enabled", 
        "SnapshotWindow": "10:00-11:00", 
        "MemberClusters": [
            "rc-rg-0001-001", 
            "rc-rg-0001-002", 
            "rc-rg-0002-001", 
            "rc-rg-0002-002", 
            "rc-rg-0002-003"
        ], 
        "PendingModifiedValues": {}
    }
}

For additional information and parameters you might want to use, see the AWS CLI topic create-replication-group.

Creating a Redis (cluster mode enabled) Replication Group from Scratch (ElastiCache API)

The following procedure creates a Redis (cluster mode enabled) replication group using the ElastiCache API.

When you create a Redis (cluster mode enabled) replication group from scratch, you create the replication group and all its nodes with a single call to the ElastiCache API CreateReplicationGroup operation. Include the following parameters.

ReplicationGroupId

The name of the replication group you are creating.

Redis (cluster mode enabled) Replication Group naming constraints

Must contain from 1 to 20 alphanumeric characters or hyphens.
Must begin with a letter.
Cannot contain two consecutive hyphens.
Cannot end with a hyphen.

ReplicationGroupDescription

Description of the replication group.

NumNodeGroups

The number of node groups you want created with this replication group. Valid values are 1 to 15.

ReplicasPerNodeGroup

The number of replica nodes in each node group. Valid values are 1 to 5.

NodeGroupConfiguration

The configuration for each node group. The NodeGroupConfiguration parameter consists of the following fields.

PrimaryAvailabilityZone – The Availability Zone where the primary node of this node group is located. If this parameter is omitted, ElastiCache chooses the Availability Zone for the primary node.

Example: us-west-2a.
ReplicaAvailabilityZones – A list of Availability Zones where the read replicas are located. The number of Availability Zones in this list must match the value of ReplicaCount. If this parameter is omitted, ElastiCache chooses the Availability Zones for the replica nodes.
ReplicaCount – The number of replica nodes in this node group.
Slots – A string that specifies the keyspace for the node group. The string is in the format startKey-endKey. If this parameter is omitted, ElastiCache allocates keys equally among the node groups.

Example: "0-4999"

CacheNodeType

The node type for each node in the replication group.

General purpose:
- Current generation:
  
  T2 node types: cache.t2.micro, cache.t2.small, cache.t2.medium
  
  M3 node types: cache.m3.medium, cache.m3.large, cache.m3.xlarge, cache.m3.2xlarge
  
  M4 node types: cache.m4.large, cache.m4.xlarge, cache.m4.2xlarge, cache.m4.4xlarge, cache.m4.10xlarge
- Previous generation: (not recommended)
  
  T1 node types: cache.t1.micro
  
  M1 node types: cache.m1.small, cache.m1.medium, cache.m1.large, cache.m1.xlarge
Compute optimized:
- Previous generation: (not recommended)
  
  C1 node types: cache.c1.xlarge
Memory optimized:
- Current generation:
  
  R3 node types: cache.r3.large, cache.r3.xlarge, cache.r3.2xlarge, cache.r3.4xlarge, cache.r3.8xlarge
  
  R4 node types: cache.r4.large, cache.r4.xlarge, cache.r4.2xlarge, cache.r4.4xlarge, cache.r4.8xlarge, cache.r4.16xlarge
- Previous generation: (not recommended)
  
  M2 node types: cache.m2.xlarge, cache.m2.2xlarge, cache.m2.4xlarge

Additional node type info

All T2 instances are created in an Amazon Virtual Private Cloud (Amazon VPC).
Redis backup and restore is not supported for T2 instances.
Redis append-only files (AOF) are not supported for T1 or T2 instances.
Redis Multi-AZ with automatic failover is not supported on T1 instances.
Redis Multi-AZ with automatic failover is supported on T2 instances only when running Redis (cluster mode enabled) - version 3.2.4 or later with the default.redis3.2.cluster.on parameter group or one derived from it.
Redis configuration variables appendonly and appendfsync are not supported on Redis version 2.8.22 and later.

CacheParameterGroup

Engine

redis

EngineVersion

3.2.4

If you want to enable in-transit or at-rest encryption on this replication group, add either or both of the TrasitEncryptionEnabled=true or AtRestEncryptionEnabled=true parameters and meet the following conditions.

Your replication group must be running Redis version 3.2.6 or 4.x.
The replication group must be created in a Amazon VPC
You must also include the parameter CacheSubnetGroup.
You must also include the parameter AuthToken with the customer specified string value for your AUTH token (password) needed to perform operations on this replication group.

Line breaks are added for ease of reading.


https://elasticache.us-west-2.amazonaws.com/
   ?Action=CreateReplicationGroup 
   &CacheNodeType=cache.m4.large
   &CacheParemeterGroup=default.redis3.2.cluster.on
   &Engine=redis
   &EngineVersion=3.2.4
   &NumNodeGroups=3
   &ReplicasPerNodeGroup=2
   &ReplicationGroupDescription=test%20group
   &ReplicationGroupId=myReplGroup
   &Version=2015-02-02
   &SignatureVersion=4
   &SignatureMethod=HmacSHA256
   &Timestamp=20150202T192317Z
   &X-Amz-Credential=<credential>

For additional information and parameters you might want to use, see the ElastiCache API topic CreateReplicationGroup.

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