Proof of concept and proposal for prioritized requests.
Feature request issue #223

This approach examines HTTP.Request before spawning a thread in the :default threadpool. If condition is true, it handles the request in the Main thread, which is a reserved thread in the :interactive pool if you launched server with -t auto,1

Proposed API

new kwarg on serve()
is_prioritized: (req::HTTP.Request) -> bool
Affects parallel mode; if the function returns true, the request will be handled in the current main thread instead of spawning a thread from the :default threadpool. This allows the server to handle requests when all :default threads are busy. The main use case is to allow health checks to respond when all worker threads are busy. For this to work, you should launch Julia with at least one dedicated interactive thread. e.g. --threads=auto,1, see Julia multi-threading documentation.

    serveparallel(
        is_prioritized = (req::HTTP.Request) -> req.target == "/health"
    )

TODO

• acceptance of implementation and config
• cleanup PR
• documentation
• test