[ENH] Introduce request priority in storage layer

[sanketkedia]

Description of changes

Summarize the changes made by this PR.

• Improvements & Bug fixes
  • ...
• New functionality
  • Introduces a notion of tagging s3 requests with their priority
  • NAC divides the total network bandwidth amongst these priority variants
  • This allocation of bandwidth distribution is configurable
  • Changes the blockfile layer to suitably tag priority of s3 requests. Currently, prefetching is low priority and everything else is high priority
  • When executing a request, NAC successively checks for bandwidth availability from lower priority channels and if any of them have availability then it dispatches the request otherwise it blocks on the semaphore of its own priority channel

Test plan

How are these changes tested?

• Tests pass locally with pytest for python, yarn test for js, cargo test for rust

Documentation Changes

None

[github-actions]

Reviewer Checklist

Please leverage this checklist to ensure your code review is thorough before approving

Testing, Bugs, Errors, Logs, Documentation

• Can you think of any use case in which the code does not behave as intended? Have they been tested?
• Can you think of any inputs or external events that could break the code? Is user input validated and safe? Have they been tested?
• If appropriate, are there adequate property based tests?
• If appropriate, are there adequate unit tests?
• Should any logging, debugging, tracing information be added or removed?
• Are error messages user-friendly?
• Have all documentation changes needed been made?
• Have all non-obvious changes been commented?

System Compatibility

• Are there any potential impacts on other parts of the system or backward compatibility?
• Does this change intersect with any items on our roadmap, and if so, is there a plan for fitting them together?

Quality

• Is this code of a unexpectedly high quality (Readability, Modularity, Intuitiveness)

[sanketkedia]

• [ENH]: Prefetch posting list in query + compactor #4257
• [ENH] Introduce request priority in storage layer #4254 👈 (View in Graphite)
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[codetheweb]

approach makes sense to me

[HammadB]

Feeback on code quality, would be nice if addressed.