When controller and compute share the same process, every HTTP request
to localhost was paying a full TCP handshake (force_close=True forced
connection teardown after each request). With 2500+ links each sending
two NIO POSTs, that's 5000 SYN->SYN-ACK->ACK cycles even for sub-ms
in-memory handlers. Switch to keep-alive for loopback compute
(127.0.0.1 / ::1 / localhost) while keeping force_close for remote
computes that may sit behind NAT/firewalls that drop idle connections.
506b0b9f4a