questions regarding autoscaling waiter conditions

[quiver]

I was about to implement autoscaling waiters for aws-cli and found that you've recently implemented it.
I have questions about specifications of autoscaling waiters, more specifically, acceptors conditions for success cases.
(I've just copied ruby-sdk's autoscaling waiter JSON to aws-cli source tree and tested from aws-cli, not from ruby-sdk.)

GroupExists API

condition

{
  "argument": "length(AutoScalingGroups)",
  "expected": 1,
  "matcher": "pathAll",
  "state": "success"
},

"length(AutoScalingGroups)" returns a scalar value and mather pathAll expects list arguments.

I think this should be

{
  "argument": "length(AutoScalingGroups)",
  "expected": 1,
  "matcher": "path",  // CHANGED
  "state": "success"
}

Same for GroupNotExists API.

GroupInService API

condition

Success condition is that ASG has at least MinSize InService instances.

{
  "argument": "contains(AutoScalingGroups[].[length(Instances[?LifecycleState=='InService']) >= MinSize][], `false`)",
  "expected": false,
  "matcher": "pathAll",
  "state": "success"
},

AutoScalingGroups[].[length(Instances[?LifecycleState=='InService']) >= MinSize][] returns a list and contains(AutoScaling ...) returns a boolean value, but mather pathAll expects list arguments.

I think this should be

{
  "argument": "contains(AutoScalingGroups[].[length(Instances[?LifecycleState=='InService']) >= MinSize][], `false`)",
  "expected": false,
  "matcher": "path",
  "state": "success"
},

or

{
  "argument": "AutoScalingGroups[].[length(Instances[?LifecycleState=='InService']) >= MinSize][]",
  "expected": true,
  "matcher": "pathAll",
  "state": "success"
}

My revised autoscaling waiter.json and a DescribeAutoScalingGroups sample output file can be found here https://gist.github.com/quiver/fca4dc97d7d5be04cf79#file-waiters-2-json.

Or am I missing something?

[awood45]

I'm going to check if there is any unexpected behavior from the waiters as written. I do know that some matcher types end up behaving in de facto the same manner, so it may not be an issue (even if not semantically optimal). I don't recall off the top of my head (returning from vacation too) which matchers are which, so I'll be looking at differences in behavior if any.

[awood45]

This is a good catch - the waiter will likely just cycle on false for a scalar with a pathAll matcher.

I'm already going to be touching Auto Scaling resources to fix another bug, so I will test and push the fix for this - no need for a PR, unless it's already done and tested.

[quiver]

@awood45

I'm already going to be touching Auto Scaling resources to fix another bug, so I will test and push the fix for this - no need for a PR, unless it's already done and tested.

I don't have a work-in-progress PR, so please do.
Thank you for your quick response. I really need this feature!

[awood45]

I've written a fix for this that will work in the case of requesting exactly one Auto Scaling group. Unfortunately, due to waiter/JMESPath limitations, if you have multiple Auto Scaling groups in a single request, something like :group_exists will return a success response if at least one group exists.

You can avoid this by always specifying a single group in your waiter requests.

[quiver]

👏