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Hello meera-k,
Thanks for the feedback.
You are correct that if you want to add an instance to a placement group, it is recommended to use a single launch request to launch all the number of instances you need.
However, this is a custom controller EC2 which may not be the OS setup (or installed applications) as the other instances inside the Placement-group. You will want to lessen your work and don’t want to recreate that custom controller, and possibly spend more time troubleshooting after recreating that instance. So you can first try to add it manually to the existing placement group.
Additionally, AWS now allows you to move an EC2 to an existing placement group https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/placement-groups.html#change-instance-placement-group.
(This is the documentation where used as reference for creating this question scenario)
The chance of getting an insufficient capacity error is not fixed. If it is just one instance, there is a good chance that the current placement group host can accommodate another instance.
Hope this helps.
Regards,
Kenneth Samonte @ Tutorials Dojo
