Datomic Knowledgebase - Recent questions tagged cloud formation

Datomic Cloud IAM role drift on setup - is this normal?

Wed, 12 Jul 2023 09:34:33 +0000

hi, just set up DC for the first time (ran the two AWS cloudformation templates). The storage stack is showing drift on the IAM managed policy datomic-admin-..., shows 'MODIFIED', in red. Is this normal upon setup? (checking the changes in the 'versions' tab, the difference is addition of autoscaling and s3 actions to the policy; the second version, presumably causing the 'drift', was added during the provisioning). Is this just a setup artifact nothing to worry about?

How create more one production compute?

Wed, 05 Jul 2023 13:54:33 +0000

Hello,
I need to use my existing storage with additional compute and tried create new production compute with this system name(storage stack name). And I get creation error:

Export with name myname-VpcLinkId is already exported by stack myname-compute. Rollback requested by user.

I understand that this is due to a name conflict, but I don’t understand how then to correctly create a compute.

I want to run my application in a separate server(сompute) but use the same storage.

Use Launch Template instead of Launch Configuration

Fri, 07 May 2021 23:38:51 +0000

The compute Datomic CloudFormation templates (primary and query groups) create ASGs using launch configurations. Launch configurations do not support the full set of Auto Scaling group features. For example, you cannot create an Auto Scaling group that launches both Spot and On-Demand Instances or that specifies multiple instance types or multiple launch templates. In fact, AWS recommends creating ASGs using launch templates, not launch configurations.

We are interested in launch templates for its support for using Spot and On-Demand instances.

EDIT: As of 2021-10-20, launch templates will not receive any new EC2 ASG features.

Make DesiredCapacity an optional parameter in the query group CF template

Wed, 24 Mar 2021 17:24:25 +0000

Currently (March 2021) the Datomic query group CF template has the DesiredCapacity parameter marked as required. Because of this, during a CF template update, CF will always set the DesiredCapacity to the CF parameter for DesiredCapacity. This behavior does not work well in the following situation.

In the query group template I have the DesiredCapacity at 2, and MaxCount at 4. I have an ASG scaling policy to target track 50% average CPU utilization. My query group is currently at the max, because the ASG scaling policy scaled up the group DesiredCapacity to 4 (to match my load). My load has increased to the point where 4 nodes is no longer sufficient. I must update the query group CF template to increase the MacCount. The problem is that when you update the MacCount from 4 to 6 via a CF template update and leave the DesiredCapacity at 2, CF will actually set the DesiredCapacity on the ASG to 2 during the high load situation. This worsens the high load situation.

One option is to query the ASG for its current DesiredCapacity prior to running a CF update and set the CF parameter to the value you retrieved. This approach complicates the update procedure. It also has a "read-modify-write" race condition -- the DesiredCapacity could have changed from the time you read the DesiredCapacity to the time you are performing the CF update.

A second option is to make the DesiredCapacity parameter optional. As per the CF docs, DesiredCapacity is not a required parameter. When it is not present, it defaults to the minimum size of the group. Leaving DesiredCapacity unset will make it so during a CF update, CF will not modify the DesiredCapacity at all -- leaving the ASG "in control."