The Gateway historian's ProcessConnectionOpen / EventConnectionOpen were
derived from read outcomes only, so a freshly booted node with a healthy
gateway reported the historian closed until a client read, and a node that
only writes (continuous historization) never flipped it.
The data source now runs a ProbeAsync loop (ServerHistorian:Gateway:
ProbeInterval, default 30 s, first probe at start-up; 0 = off). Each probe,
bounded at 10 s, is recorded as the latest connectivity observation; the
latest observation (probe or read) is what the snapshot reports. Probes never
touch the query/failure counters. DisposeAsync stops the loop before
disposing the client.
Rebased from the unpushed remed/lane-H2 branch (originally authored 2026-10-22
in session_01Ub9hGmYLQvn9XETzw7CMsT) onto current master.
Claude-Session: https://claude.ai/code/session_01GT67AEHd2Acv1YPwGfXEoV
Joseph Doherty