68f23f57d77bc172ed39ecdd4d2d5cd5e13cf483 http: bugfix: track closed connection (stickies-v)
084d0372311e658a486622f720d2b827d8416591 http: log connection instead of request count (stickies-v)
41f9027813f849a9fd6a1479bbb74b9037990c3c http: refactor: use encapsulated HTTPRequestTracker (stickies-v)
Pull request description:
#26742 significantly increased the http server shutdown speed, but also introduced a bug (#27722 - see https://github.com/bitcoin/bitcoin/issues/27722#issuecomment-1559453982 for steps to reproduce on master) that causes http server shutdown to halt in case of a remote client disconnection. This happens because `evhttp_request_set_on_complete_cb` is never called and thus the request is never removed from `g_requests`.
This PR fixes that bug, and improves robustness of the code by encapsulating the request tracking logic. Earlier approaches (#27909, #27245, #19434) attempted to resolve this but [imo are fundamentally unsafe](https://github.com/bitcoin/bitcoin/pull/27909#discussion_r1265614783) because of differences in lifetime between an `evhttp_request` and `evhttp_connection`.
We don't need to keep track of open requests or connections, we just [need to ensure](https://github.com/bitcoin/bitcoin/pull/19420#issue-648067169) that there are no active requests on server shutdown. Because a connection can have multiple requests, and a request can be completed in various ways (the request actually being handled, or the client performing a remote disconnect), keeping a counter per connection seems like the approach with the least overhead to me.
Fixes#27722
ACKs for top commit:
vasild:
ACK 68f23f57d77bc172ed39ecdd4d2d5cd5e13cf483
theStack:
ACK 68f23f57d77bc172ed39ecdd4d2d5cd5e13cf483
Tree-SHA512: dfa711ff55ec75ba44d73e9e6fac16b0be25cf3c20868c2145a844a7878ad9fc6998d9ff62d72f3a210bfa411ef03d3757b73d68a7c22926e874c421e51444d6
db7b5dfcc5