add full AZ awareness to plugin scraping interfaces #358
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This is the first half of a refactor of the scrape methods towards full AZ awareness. Scraping can return data either for the entire region, or broken down by AZs. This distinction is represented by the enum type Topological. For capacity scraping, this does not present a huge change, because several capacitors already report capacity by AZ. What changes is that: - subcapacities are now reported on the AZ (instead of regional) level - the region-wide capacity is computed outside of the plugin by summing the individual AZ capacities The frontend does not change in any way at this point. These changes will come later, once the user-visible changes have been agreed upon. This changeset is about preparing the things that we will definitely need, and making data available to the collector that we will need to surface in the frontend later on.
This is the second part of the change that was started in the previous commit. This change is much more straight-forward than the one to the capacity plugins, since quota plugins do not report usage per AZ at all right now. We are still evaluating which plugins to move to per-AZ usage reporting and which changes in the backend services will be necessary to enable this.
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Depending on the resource, scraping can now return capacity and usage data either for the entire region, or broken down by AZs. This distinction is represented by the enum type
core.Topological. Quota stays affixed to the regional level for now (i.e. one number that applies across all AZs), since there is no committed requirement to support AZ quota in the backend.The frontend does not change in any way at this point. This change is specifically about enhancing the interface between Limes internals and plugins to the point that whatever changes end up being done in the frontend can be supported.
Some more details are in the commit messages.
Update: I have tested that the new plugin implementations yield the same results. There are some exceptions for
sharev2/share_capacityandcompute/instances, where, because of rounding errors, computing the total capacity from raw values (as we did before) is different from computing the capacity per AZ from raw values and then summing over all AZs. These are literal rounding errors, though.