Shutdown

By default SIGTERM and SIGINT end the process right away, without waiting for the requests in progress, and release what the server holds (the files of /disk). To see what an orchestrator or a load balancer does during a rollout, set SHUTDOWN_GRACE_SECONDS: the server then drains first.

• It closes the port, so a new connection is refused, and keeps serving the requests and the connections that are already open.
• It writes what is going on every second: Draining, 3 s: 2 requests and 5 connections open.
• It ends when nothing is open (Drained after 2.4 s) or when the grace period is over, whichever comes first, and releases what it holds then. A second signal ends it at once.
• While it drains, /info (shutdown) and /metrics (torchio_draining, torchio_open_requests, torchio_open_connections) say so, for a client that still has a connection open: it is served as before, and a connection that stays idle keeps the drain waiting.

docker run -p 3000:3000 -e SHUTDOWN_GRACE_SECONDS=30 altrdev/torchio

/delay and /connections make something to wait for: /delay?ms=10000 is a request in progress, and /connections?count=50&hold=60 leaves 50 connections open that the drain waits for until the grace period is over. In Kubernetes, terminationGracePeriodSeconds must be longer than SHUTDOWN_GRACE_SECONDS, or the kubelet ends the container first.