(4/5) [nexus] Consider Affinity/Anti-Affinity Groups during instance placement #7446
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hawkw
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Jan 31, 2025
smklein
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Feb 25, 2025
…#7447) Pulled out of #7076 This PR is a partial implementation of RFD 522 It adds: - Affinity and Anti-Affinity groups, contained within projects. These groups are configured with a **policy** and **failure domain** can currently contain zero or more **members**. Affinity groups attempt to co-locate members, anti-affinity groups attempt to avoid co-locating members. - **Policy** describes "what to do if we cannot fulfill the co-location request". Currently, these options are "fail" (reject the request) or "allow" (continue with provisioning of the group member regardless). - **Failure Domain** describes the scope of what is considered "co-located". In this PR, the only option is "sled", but in the future, this may be expanded to e.g. "rack". - **Members** describe what can be added to affinity/anti-affinity groups. In this PR, the only option is "instance". RFD 522 describes how "anti-affinity groups may also contain affinity groups" -- which is why this "member" terminology is introduced -- but it is not yet implemented. - (anti-)Affinity groups are exposed by the API, through a CRUD interface - (anti-)Affinity groups are considered during "sled reservation", where instances are placed on a sled. This is most significantly implemented (and tested) within `nexus/db-queries/src/db/datastore/sled.rs`, within #7446 Fixes #1705
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Pulled out of #7076
Modifies the instance placement logic to consider affinity and anti-affinity groups.
This is still technically "internal-only", because the HTTP endpoints to create affinity groups are, as of this PR, still unimplemented.