Monitor systemd Socket Activation and Alert on Queue Depth
When systemd hands a listening socket to a service, the kernel keeps completed connections in an accept queue until the service calls accept() on them. If the service falls behind — thread-starved, blocked on a slow database, whatever — that queue fills. Past the socket's backlog it silently drops or refuses connections. This guide sets up a small, read-only monitor that watches the accept-queue depth on your listening sockets and raises an alert before you hit that wall.







































































