How do you remove/undo/delete a pending modification on Amazon Aurora RDS?

Question

I was pegging the 90 total connections allowed on my Aurora RDS instance, now that I've got a few more heavy duty sites than I had before. I decided to upgrade the instance and I did so, but put the upgrade as pending until the next maintenance window, without considering adding a read-only replica into the cluster. I've added the replica and all is well. I want to cancel that pending upgrade from a db.t2.medium Aurora to a db.r3.large Aurora instance. I can't find a way to clear out the pending modifications queue.

I have the AWS CLI installed and config'd. I just can't find documentation on flushing out the pending modifications queue. Thanks to all in advance.

Answer 1

As @gileri described, there is now a way to undo a pending modification.

I tested it multiple times with RDS/Aurora instances and it works as expected, even without the --apply-immediately parameter (at least for the instance class modifications).

Full Example

Let's change the instance class for an Aurora instance called database-2-instance-1 from db.t3.medium to db.r4.large and undo it again afterwards. None of these commands do impact the availability of the database.

Note: Using jq here to only output the important parts.

Check instance class

$ aws rds describe-db-instances --db-instance-identifier database-2-instance-1 | jq '.DBInstances[].DBInstanceClass'
"db.t3.medium"

Validate that there is no pending modification

$ aws rds describe-db-instances --db-instance-identifier database-2-instance-1 | jq '.DBInstances[].PendingModifiedValues'
{}

Modify instance class

This modification will result in a change of the instance class in the next maintenance window.

$ aws rds modify-db-instance --db-instance-identifier database-2-instance-1 --db-instance-class db.r4.large | jq '.DBInstance.PendingModifiedValues'
{
  "DBInstanceClass": "db.r4.large"
}

Validate again

Just to be sure, check if everything looks as expected.

$ aws rds describe-db-instances --db-instance-identifier database-2-instance-1 | jq '.DBInstances[].PendingModifiedValues'
{
  "DBInstanceClass": "db.r4.large"
}

Undo modify of instance class

This is the important part which modifies the instance class back to the old value. The documentation describes that a --apply-immediately is required, but it turns out that that is not the case. At least in this example.

$ aws rds modify-db-instance --db-instance-identifier database-2-instance-1 --db-instance-class db.t3.medium | jq '.DBInstance.PendingModifiedValues'
{}

Validate the removed pending modification

$ aws rds describe-db-instances --db-instance-identifier database-2-instance-1 | jq '.DBInstances[].PendingModifiedValues'
{}

At this point the pending modification is gone.

Answer 2

Since February 2019, it is documented that you can cancel such pending modifications. I have tested this with a pending DB instance class modification.

If you don't want a pending change to be applied in the next maintenance window, you can modify the DB instance to revert the change using the AWS CLI and specify the --apply-immediately option.