Dynamic components (component switcher)

Dynamic components (component switcher)

The ComponentSwitcher is a module within the blockserver which is responsible for dynamically editing configurations in response to a PV value update. It adds and removes components to all configurations to achieve this.

Configuration

The config switcher configuration file is in

C:\Instrument\Settings\config\...\configurations\ComponentSwitcher\component_switcher.json

and has a structure similar to the following:

[
    {
        "pv": "PARS:USER:R0",
        "is_local": true,
        "value_to_component_map": {
            "0.0": "test1",
            "1.0": "test2"
        }
    }
]

Where:

• pv is the PV which should be monitored for changes
• is_local controls whether the local PV prefix should be prepended to the PV before the monitor is created
• value_to_component_map is a dict mapping the pv values as strings to dynamic components which should be added
  • These values must be strings as they are JSON dict keys. The monitor will cast all received values using str()

Overview

When a monitor is received, the following actions take place:

• The value is cast to a string
• If the value has a non-zero STAT or SEVR, the update is logged but then ignored (we don't want to change configs based on an invalid value from hardware)
• If the value is not present as a key in value_to_component_map, the update is ignored and an error is logged
• For each configuration:
  • Remove all components which are present in both the configuration and the value_to_component_map, except the component which corresponds to the value just recieved
  • Add the component which corresponds to the value in value_to_component_map, if it was not already present
  • If the configuration changed, save it to disk
  • If this is the current configuration and it changed, reload the config to get the changes