sands-lab/nika/host-crash-skill

host_crash

Fingerprint (all three must be true → submit)

• ICMP to the device's known IP fails. Look up the IP via a peer or safe_reachability; do not rely on a name that the device itself resolves.
• Shell on the device times out or never opens — exec_shell, infra_sweep exec_failed, and safe_reachability all fail on that device.
• Same-role peer baseline stays clean. Other hosts/servers of the same kind remain reachable, the routing fabric is healthy, and no widespread cascade is in play.

All three must hold. Any partial response rules out host_crash.

Submit

• is_anomaly=True
• root_cause_name=["host_crash"]
• faulty_devices=["<device>"]

Not load_balancer_overload

If the unresponsive device is the load balancer and it still answers ICMP, localhost HTTP, or any partial VIP probe, that is probably load_balancer_overload. Use load-balancer-skill.

Not sender/receiver_resource_contention

An isolated exec_failed/timeout on one web/app server or one client, while ICMP still answers or same-role peers are otherwise clean, is resource contention — not crash. Use resource-contention-skill. host_crash requires full silence and a clean same-role baseline.

Not upstream cascade

If many same-role devices are unreachable together, or the routing/control-plane fabric is broken, the cause is upstream (link, ACL, OSPF/BGP, DHCP relay). Rerun the matching broad-search helper before submitting host_crash.