Changing the configuration without a restart

Operations guide: configure, deploy and observe the gateway. What the capability does, product side: product guide; calling it: developer guide.

Goal: add a route, tune a quota, serve a second API - without a restart and without losing a request.

Command - edit the file; the gateway reads flexway.yaml and its contracts again every 5 s (server.reload.interval):

$EDITOR openapi.yaml
docker kill -s HUP flexway        # optional: take the change at once

A second API, on its own host, from its own contract:

hosts:
  admin.example.com:
    default_upstream: backoffice
    contracts: [./admin.yaml]       # this host serves exactly this contract, nothing of openapi.yaml

Check: /config (admin port) shows a new config_version, a new config_digest (the semantic digest flexway validate prints) and last_reload.result: applied. A deliberate mistake - an upstream that does not exist - replaces nothing: the running configuration keeps serving, last_reload.result: rejected, the cause in last_reload.cause and in the log, once.

Eight settings need a restart: server.shutdown, server.reload, server.counters, server.shedding, server.in_flight, server.cache, server.tls and observability. Changing one refuses the whole reload, naming the key. Requests in flight finish on the previous configuration, streams included.