How does one update a CF stack?

(Say we need to size up our ec2 instance)

1. Submit updated template
2. CF compares changes
3. Only changed resources are changed

Ways:

1. “Direct Update” (just go for it)
2. “Change set” (Gives ability to do a dry-run / preview)

Potential update behaviors?

(Varies by resource type)

1. Update w/ no interruption

• Updates resource w/o disrupting ops nor physical ID
• E.g. Instance profile

2. Update w/ some interruption

• Updates w/ some interruption. Physical ID retained
• E.g. HostId

3. Replacement

• Total recreation / new physical ID.
• E.g. availability zone

Direct changes or change sets?

• Change sets are good for prod
• Direct is fine for dev or test

How to utilize update behaviors?

• Dictates how to modify resources
• Don’t do a full “replacement” if you need to retain physical ID label