Use softioc.autosave in an IOC

Creating an IOC shows how to create a pythonSoftIOC.

Example IOC

from softioc import autosave, builder, softioc
import cothread

# Set the record prefix
builder.SetDeviceName("MY-DEVICE-PREFIX")

# Create records, set some of them to autosave, also save some of their fields

builder.aOut("AO", autosave=True)
builder.aIn("AI", autosave=["PREC", "EGU"])
builder.boolIn("BO")
builder.WaveformIn("WAVEFORMIN", [0, 0, 0, 0], autosave=True)
with autosave.Autosave(["VAL", "LOPR", "HOPR"]):
    builder.aOut("AUTOMATIC-AO", autosave=["EGU"])
seconds = builder.longOut("SECONDSRUN", autosave=True)

autosave.configure(
    directory="/tmp/autosave-data",
    name="MY-DEVICE-PREFIX",
    save_period=5.0
)

builder.LoadDatabase()
softioc.iocInit()

# Start processes required to be run after iocInit
def update():
    while True:
        cothread.Sleep(1)
        seconds.set(seconds.get() + 1)

cothread.Spawn(update)

softioc.interactive_ioc(globals())

Records are instantiated as normal and configured for automatic loading and periodic saving to a backup file with use of the keyword argument autosave. autosave resolves to a list of strings, which are the names of fields to be tracked by autosave. By default autosave=False, which disables autosave for that PV. Setting autosave=True is equivalent to passing ["VAL"]. Note that "VAL" must be explicitly passed when tracking other fields, e.g. ["VAL", "LOPR", "HOPR"]. autosave can also accept a single string field name as an argument.

The field values get written into a yaml-formatted file containing key-value pairs. By default the keys are the same as the full PV name, including any device name specified in SetDeviceName().

Autosave is disabled until configure() is called. The first two arguments, directory and name are required. Backup files are periodically written into directory with the name <name>.softsav every save_period seconds, set to 30.0 by default. The directory must exist, and should be configured with the appropriate read/write permissions for the user running the IOC.

IOC developers should only need to interface with autosave via the configure() method and the autosave keyword argument. Alternatively, PVs can be instantiated inside the Autosave() context manager, which automatically passes the autosave argument to any PVs created inside the context manager. If any fields are already specified by the autosave keyword argument of a PV’s initialisation call the lists of fields to track get combined. All other module members are intended for internal use only.

In normal operation, loading from a backup is performed once during the LoadDatabase() call and periodic saving to the backup file begins when iocInit() is called, provided that any PVs are configured to be saved. Currently, manual loading from a backup at runtime after ioc initialisation is not supported. Saving only occurs when any of the saved field values have changed since the last save. Users are discouraged from manually editing the backup files while the IOC is running so that the internal state of the autosave thread is consistent with the backup file.

If autosave is enabled and active, a timestamped copy of the latest existing autosave backup file is created when the IOC is restarted, e.g. <name>.softsav_240717-095004 (timestamps are in the format yymmdd-HHMMSS). If you only wish to store one backup of the autosave file at a time, timestamped_backups=False can be passed to configure() when it is called, this will create a backup file named <name>.softsav.bu. To disable any autosaving, comment out the configure() call or pass it the keyword argument enabled=False.

The resulting backup file after running the example IOC for about 30 seconds is the following:

MY-DEVICE-PREFIX:AI.EGU: ''
MY-DEVICE-PREFIX:AI.PREC: '0'
MY-DEVICE-PREFIX:AO: 0.0
MY-DEVICE-PREFIX:AUTOMATIC-AO: 0.0
MY-DEVICE-PREFIX:AUTOMATIC-AO.EGU: ''
MY-DEVICE-PREFIX:AUTOMATIC-AO.HOPR: '0'
MY-DEVICE-PREFIX:AUTOMATIC-AO.LOPR: '0'
MY-DEVICE-PREFIX:SECONDSRUN: 29
MY-DEVICE-PREFIX:WAVEFORMIN: [0, 0, 0, 0]

If the IOC is stopped and restarted, the SECONDSRUN record will load its saved value of 29 from the backup. All non-VAL fields are stored as strings. Waveform type records holding arrays are cast into lists before saving.

This example IOC uses cothread, but autosave works identically when using an asyncio dispatcher.