Replace "Max spot instance requests per region" limit with vCPU-based limits

[TagadaPoe]

Summary

BREAKING CHANGE

As mentioned in issue #502, the limit "Max spot instance requests per region" was removed from AWS and replaced by the following limits, based on the number of vCPU:

• All F Spot Instance Requests
• All G Spot Instance Requests
• All Inf Spot Instance Requests
• All P Spot Instance Requests
• All Standard (A, C, D, H, I, M, R, T, Z) Spot Instance Requests
• All X Spot Instance Requests

As a result, the usage reported by awslimitchecker is not relevant anymore.

In order to fix this, this commit replaces the call to the EC2 API describe_spot_instance_requests() with a call to the CloudWatch API, since the usage of Spot requests vCPUs is now available as a metric in CloudWatch.

In addition, the applied limits are now retrieved from the Service Quotas service.

Pull Request Checklist

• All pull requests should be against the develop branch, not master.
• All pull requests must include the Contributor License Agreement (see below).
• Whether or not your PR includes unit tests:
  • Please make sure you have run the exact code contained in the PR locally, and it functions as desired.
  • Please make sure the TravisCI build passes or, if not, you've corrected any obvious problems identified by the tests.
• Code should conform to the Development Guidelines:
  • pep8 compliant with some exceptions (see pytest.ini)
  • 100% test coverage with pytest (with valid tests). If you have difficulty
    writing tests for the code, that's fine, just mention that in the summary and either
    ask for assistance, or clarify that you'd like someone else to handle the tests. PRs that
    include complete test coverage will usually be merged faster.
  • Complete, correctly-formatted documentation for all classes, functions and methods.
  • documentation has been rebuilt with tox -e docs
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    connect() and connect_resource() methods, inherited from
    awslimitchecker.connectable.Connectable
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Contributor License Agreement

By submitting this work for inclusion in awslimitchecker, I agree to the following terms:

• The contribution included in this request (and any subsequent revisions or versions of it)
  is being made under the same license as the awslimitchecker project (the Affero GPL v3,
  or any subsequent version of that license if adopted by awslimitchecker).
• My contribution may perpetually be included in and distributed with awslimitchecker; submitting
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[jantman]

@TagadaPoe I'm going to try to get to these PRs today, sorry for the delay. Could you please update your PR to allow changes from maintainers? This needs to be rebased on develop, and the others will need to be rebased as I merge them in. Thanks!

[jantman]

@TagadaPoe The code here looks good to me, but I'm a little confused by the default limits? In this PR I see the defaults as mostly 128 or 64, but at https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/using-spot-limits.html they seem to be much lower, i.e. 11 or 16 for many. Would you be so kind as to explain... I think I'm missing something here, or confused.

[TagadaPoe]

@TagadaPoe I'm going to try to get to these PRs today, sorry for the delay. Could you please update your PR to allow changes from maintainers? This needs to be rebased on develop, and the others will need to be rebased as I merge them in. Thanks!

I cannot see the "Allow edits from maintainers" link, is this because the PR is already in the "jantman/awslimitchecker repository" ?

[TagadaPoe]

@TagadaPoe The code here looks good to me, but I'm a little confused by the default limits? In this PR I see the defaults as mostly 128 or 64, but at https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/using-spot-limits.html they seem to be much lower, i.e. 11 or 16 for many. Would you be so kind as to explain... I think I'm missing something here, or confused.

I fixed that, I am not sure where I took those values from...

[codecov-commenter]

Codecov Report

Merging #547 (bbeced3) into develop (a829ce2) will not change coverage.
The diff coverage is 100.00%.

❗ Current head bbeced3 differs from pull request most recent head cbe9040. Consider uploading reports for the commit cbe9040 to get more accurate results

@@            Coverage Diff            @@
##           develop      #547   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           42        42           
  Lines         3030      3025    -5     
  Branches       455       453    -2     
=========================================
- Hits          3030      3025    -5     

Impacted Files	Coverage Δ
awslimitchecker/services/ec2.py	100.00% <100.00%> (ø)

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[antonincms]

Hello @jantman, as said by @TagadaPoe we couldn't find the option to allow you to rebase our branch.
Maybe this is related to some parameters in our org or something else.

Anyway, I rebased all three branches, don't hesitate to ping me if you need rebasing or anything else.

[jantman]

Thank you so much for this, and apologies for the delay in merging it!

[jantman]

This has been released in 12.0.0, which is now live on PyPI and Docker Hub. Thank you so much, and apologies for the delay!