Two-tier fix for a namespace recording's "channel with zero updates
is simply absent from the file" gap:
1. RecordingSession.start() now seeds a channel with its current value
(add_current_value=True) when that's actually free: pyepics'
PV.get_with_metadata() returns the cached value with no CA traffic
when auto_monitor is already True and the channel is connected -
true for the large majority of channels under ca_tuning.make_pv()'s
default policy. A demoted "fast" channel or a disconnected one
would make this a real blocking get, so those are left unseeded, as
before. New n_seeded counter reports how many got the free seed.
2. For the rest, RecordingSession.backfill_from_status() lets a status
snapshot that was already being taken for another reason (a scan's
own status_run_start/status_run_end capture) opportunistically fill
in one value for any channel still at zero points - never a trigger
of new CA traffic on its own. NamespaceMonitorStore gains
pgroup/run_number on start_recording() (purely for this lookup) and
backfill_running_recordings(), wired into both /status/capture and
/status/snapshot right after their own snapshot() call. New
n_backfilled counter.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
lemke_handClaude Sonnet 5
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