Graceful shutdown of ASP.NET Core pods in Kubernetes: SIGTERM and grace period (Kubernetes YAML)

# ======================================================================
# Q: What happens when Kubernetes stops a pod? How do you shut down gracefully?
#
# - The pod is removed from the Service endpoints and, at the same time, the
#   container receives SIGTERM.
# - The .NET host triggers ApplicationStopping. Kestrel stops accepting new
#   requests and completes the in-flight ones. BackgroundServices get
#   cancellation through the stoppingToken.
# - If it doesn't finish within terminationGracePeriodSeconds (default 30s),
#   SIGKILL follows.
# - Workers: honor the CancellationToken. A message that was not finished is not
#   completed, so it gets redelivered (Q30), which is why the consumer must be
#   idempotent (Q31).
# - Memory: .NET reads the container's memory limit (cgroups) and sizes the GC
#   heap accordingly (default ~75% of the limit). If the pod gets OOMKilled,
#   look for a leak first (Q44) and only then raise the limit.
# - CPU limits cause throttling, which looks like random latency. We often set
#   only CPU requests, without limits.
# ======================================================================

# Deployment: a short wait so the load balancer stops sending traffic before SIGTERM
spec:
  terminationGracePeriodSeconds: 30
  containers:
    - name: api
      lifecycle:
        preStop:
          # native sleep (Kubernetes 1.30+): the chiseled image has no /bin/sleep
          sleep: { seconds: 5 }