I have a heavy used RDS instance (MySQL) in EC2-Classic with three read replica instances. We're on plan to move some of our micro-services into VPC and some of them need to read on those replica instances (we have not plans to move completely those RDS instances to VPC in the medium term). The first thought that came to my mind was to create a read replica inside the VPC (I have already a subnet-group created), but I got an error message:
At least one security group 'xxxxx' (Non-VPC) and subnet group 'dbsubnetgroup' (in VPC 'vpc-123456') are not in common VPC. (Service: AmazonRDS; Status Code: 400; Error Code: InvalidParameterCombination; Request ID: 5a8f57fb-f5b4-11e5-996f-d16e3527730f)
I've tried to achieve this using the AWS CLI:
aws rds create-db-instance-read-replica --db-instance-identifier replica-name --source-db-instance-identifier spurce-name --db-subnet-group-name sbsubnetgroup-name --region us-east-1 A client error (DBSubnetGroupNotAllowedFault) occurred when calling the CreateDBInstanceReadReplica operation: DbSubnetGroupName should not be specified for read replicas that are created in the same region as the master
So, as far I see, this kind of replication is not allowed within the same region but it only works in a cross-region fashion?
Is there a way to solve it?
Thanks in advance