Adding Aurora Replicas to a DB cluster - Amazon Aurora

Adding Aurora Replicas to a DB cluster

An Aurora DB cluster with replication has one primary DB instance and up to 15 Aurora Replicas. The primary DB instance supports read and write operations, and performs all data modifications to the cluster volume. Aurora Replicas connect to the same storage volume as the primary DB instance, but support read operations only. You use Aurora Replicas to offload read workloads from the primary DB instance. For more information, see Aurora Replicas.

Amazon Aurora Replicas have the following limitations:

  • You can't create an Aurora Replica for an Aurora Serverless v1 DB cluster. Aurora Serverless v1 has a single DB instance that scales up and down automatically to support all database read and write operations.

    However, you can add reader instances to Aurora Serverless v2 DB clusters. For more information, see Adding an Aurora Serverless v2 reader.

We recommend that you distribute the primary instance and Aurora Replicas of your Aurora DB cluster over multiple Availability Zones to improve the availability of your DB cluster. For more information, see Region availability.

To remove an Aurora Replica from an Aurora DB cluster, delete the Aurora Replica by following the instructions in Deleting a DB instance from an Aurora DB cluster.

Note

Amazon Aurora also supports replication with an external database, such as an RDS DB instance. The RDS DB instance must be in the same AWS Region as Amazon Aurora. For more information, see Replication with Amazon Aurora.

You can add Aurora Replicas to a DB cluster using the AWS Management Console, the AWS CLI, or the RDS API.

To add an Aurora replica to a DB cluster

  1. Sign in to the AWS Management Console and open the Amazon RDS console at https://console.aws.amazon.com/rds/.

  2. In the navigation pane, choose Databases, and then select the DB cluster where you want to add the new DB instance.

  3. Make sure that both the cluster and the primary instance are in the Available state. If the DB cluster or the primary instance are in a transitional state such as Creating, you can't add a replica.

    If the cluster doesn't have a primary instance, create one using the create-db-instance AWS CLI command. This situation can arise if you used the CLI to restore a DB cluster snapshot and then view the cluster in the AWS Management Console.

  4. For Actions, choose Add reader.

    The Add reader page appears.

  5. On the Add reader page, specify options for your Aurora Replica. The following table shows settings for an Aurora Replica.

    For this option Do this

    Availability zone

    Determine if you want to specify a particular Availability Zone. The list includes only those Availability Zones that are mapped to the DB subnet group that you chose when you created the DB cluster. For more information about Availability Zones, see Regions and Availability Zones.

    Publicly accessible

    Select Yes to give the Aurora Replica a public IP address; otherwise, select No. For more information about hiding Aurora Replicas from public access, see Hiding a DB cluster in a VPC from the internet.

    Encryption

    Select Enable encryption to enable encryption at rest for this Aurora Replica. For more information, see Encrypting Amazon Aurora resources.

    DB instance class

    Select a DB instance class that defines the processing and memory requirements for the Aurora Replica. For more information about DB instance class options, see Aurora DB instance classes.

    Aurora replica source

    Select the identifier of the primary instance to create an Aurora Replica for.

    DB instance identifier

    Enter a name for the instance that is unique for your account in the AWS Region you selected. You might choose to add some intelligence to the name such as including the AWS Region and DB engine you selected, for example aurora-read-instance1.

    Priority

    Choose a failover priority for the instance. If you don't select a value, the default is tier-1. This priority determines the order in which Aurora Replicas are promoted when recovering from a primary instance failure. For more information, see Fault tolerance for an Aurora DB cluster.

    Database port

    The port for an Aurora Replica is the same as the port for the DB cluster.

    DB parameter group

    Select a parameter group. Aurora has a default parameter group you can use, or you can create your own parameter group. For more information about parameter groups, see Working with parameter groups.

    Performance Insights

    The Turn on Performance Insights check box is selected by default. The value isn't inherited from the writer instance. For more information, see Monitoring DB load with Performance Insights on Amazon Aurora.

    Enhanced monitoring

    Choose Enable enhanced monitoring to enable gathering metrics in real time for the operating system that your DB cluster runs on. For more information, see Monitoring OS metrics with Enhanced Monitoring.

    Monitoring Role

    Only available if Enhanced Monitoring is set to Enable enhanced monitoring. Choose the IAM role that you created to permit Amazon RDS to communicate with Amazon CloudWatch Logs for you, or choose Default to have RDS create a role for you named rds-monitoring-role. For more information, see Monitoring OS metrics with Enhanced Monitoring.

    Granularity

    Only available if Enhanced Monitoring is set to Enable enhanced monitoring. Set the interval, in seconds, between when metrics are collected for your DB cluster.

    Auto minor version upgrade

    Select Enable auto minor version upgrade if you want to enable your Aurora DB cluster to receive minor DB Engine version upgrades automatically when they become available.

    The Auto minor version upgrade setting applies to both Aurora PostgreSQL and Aurora MySQL DB clusters. For Aurora MySQL 2.x clusters, this setting upgrades the clusters to a maximum version of 2.07.2.

    For more information about engine updates for Aurora PostgreSQL, see Amazon Aurora PostgreSQL updates.

    For more information about engine updates for Aurora MySQL, see Database engine updates for Amazon Aurora MySQL.

  6. Choose Add reader to create the Aurora Replica.

To create an Aurora Replica in your DB cluster, run the create-db-instance AWS CLI command. Include the name of the DB cluster as the --db-cluster-identifier option. You can optionally specify an Availability Zone for the Aurora Replica using the --availability-zone parameter, as shown in the following examples.

For example, the following command creates a new MySQL 5.7–compatible Aurora Replica named sample-instance-us-west-2a.

For Linux, macOS, or Unix:

aws rds create-db-instance --db-instance-identifier sample-instance-us-west-2a \
    --db-cluster-identifier sample-cluster --engine aurora-mysql --db-instance-class db.r5.large \
    --availability-zone us-west-2a

For Windows:

aws rds create-db-instance --db-instance-identifier sample-instance-us-west-2a ^
    --db-cluster-identifier sample-cluster --engine aurora-mysql --db-instance-class db.r5.large ^
    --availability-zone us-west-2a

The following command creates a new MySQL 5.7–compatible Aurora Replica named sample-instance-us-west-2a.

For Linux, macOS, or Unix:

aws rds create-db-instance --db-instance-identifier sample-instance-us-west-2a \
    --db-cluster-identifier sample-cluster --engine aurora-mysql --db-instance-class db.r5.large \
    --availability-zone us-west-2a

For Windows:

aws rds create-db-instance --db-instance-identifier sample-instance-us-west-2a ^
    --db-cluster-identifier sample-cluster --engine aurora --db-instance-class db.r5.large ^
    --availability-zone us-west-2a

The following command creates a new PostgreSQL-compatible Aurora Replica named sample-instance-us-west-2a.

For Linux, macOS, or Unix:

aws rds create-db-instance --db-instance-identifier sample-instance-us-west-2a \
    --db-cluster-identifier sample-cluster --engine aurora-postgresql --db-instance-class db.r5.large \
    --availability-zone us-west-2a

For Windows:

aws rds create-db-instance --db-instance-identifier sample-instance-us-west-2a ^
    --db-cluster-identifier sample-cluster --engine aurora-postgresql --db-instance-class db.r5.large ^
    --availability-zone us-west-2a

To create an Aurora Replica in your DB cluster, call the CreateDBInstance operation. Include the name of the DB cluster as the DBClusterIdentifier parameter. You can optionally specify an Availability Zone for the Aurora Replica using the AvailabilityZone parameter.