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Daniel Jomphe20:08:45

Hi! With the new Datomic Cloud, if I set a compute group's auto scaling configuration with desired capacity to 1 and minimum number of instances during update to 2, should it spin up a 2nd instance when the update starts before applying the new app code, in order to enable high availability during deployments, and scale back to the desired capacity after the deployment succeeds?

Daniel Jomphe20:08:01

Here is how I set it up.

Daniel Jomphe20:08:57

I tested it and the system/ASG didn't scale up a 2nd instance during the deployment, so it caused downtime. Are my expectations wrong about setting it up like I did?


That "min during update" is for Cloud Formation updates (eg. updating to a new Datomic release.) Not Code Deploy. Code Deploy d_eploy_ to running instances. If you want HA during a Code Deploy you would need to have the desired instances set to 2.

Daniel Jomphe13:08:34

Oh, and it was written in the descriptive label just like you say...! Thanks! 😲

Daniel Jomphe13:08:35

I'm quite impressed to see that it's possible to perform HA compute group updates. 🙂 And @U1QJACBUM then in case I need this someday on a compute group with Desired Capacity set to 1... In that case, if min during update is 1, will the CloudFormation update scale up to 2 instances temporarily to ensure at least 1 instance is always running during the update? And what if min during update is 2 but desired capacity is 1?


If min during update is 1, yes CF should scale up to 2 during an upgrade and then kill the previous instance as long as the maximum allows for that. For the second question if it is 2 then 2 instances will run, but again you have to have ceiling from max.

Daniel Jomphe16:08:07

Thanks for the confirmation!