`filewriter`: selog blocks

Comienza en el punto de entrada de filewriter y sigue cómo las actualizaciones de bloques se convierten en salida .nxs. Compara las rutas raw_data_1/selog/ requeridas con el writer actual, incluida la búsqueda histórica necesaria para la actualización inicial. Se considera terminado cuando se escriben todos los campos indicados para cada bloque y se resuelve la decisión sobre la representación del registro de cadenas.

The filewriter must be able to write the selog data.

For each block, this includes:

• raw_data_1/selog/<block>/read_control (was a LabVIEW VI control name; not populated by current system; could be populated as EPICS PV name)
• raw_data_1/selog/<block>/set_control (was a LabVIEW VI control name; not populated by current system)
• raw_data_1/selog/<block>/setpoint
• raw_data_1/selog/<block>/setpoint_spread
• raw_data_1/selog/<block>/value
• raw_data_1/selog/<block>/value_log/alarm_severity
• raw_data_1/selog/<block>/value_log/alarm_status
• raw_data_1/selog/<block>/value_log/alarm_time
• raw_data_1/selog/<block>/value_log/name
• raw_data_1/selog/<block>/value_log/time
• raw_data_1/selog/<block>/value_log/value
• raw_data_1/selog/<block>/value_log/value_valid
• raw_data_1/selog/<block>/value_spread
• raw_data_1/selog/<block>/vi_name (was a LabVIEW VI name; not populated by current system)

[!IMPORTANT]
When implementing, we must ensure that the filewriter 'goes back' in time to find the most recent update for each block and log that as the initial update. Otherwise, values will be missing in the .nxs until the block happens to update or the forwarder happens to schedule one of it's periodic updates. For short runs and blocks that don't update much, it is possible that may never happen.

Questions

The ISISICP currently writes strings in a way that is not nexus-compliant. Do we want to continue to do that?

There is a new NXtextlog nexus class for storing string-logs, and as ESS vs00 schema for emitting string-type updates through Kafka.

Potential differences from existing files

• The update frequency of blocks logged here may be different than old system; streaming system will see and be able to log all block updates (unless we choose to implement downsampling)