Modes

The three modes the middleware can run in, and which are implemented.

The three middleware modes as constants. Do not use bare strings.

SemanticMiddleware(mode=...) took a plain str. It validated the string against a tuple. The tuple was written out at the call site. A typo produced a ValueError at construction. This is at least loud. Nothing made the valid values discoverable. Every comparison in the class restated one of the literals.

Use a str subclass. Do not use a plain Enum. This is deliberate. Every existing caller passes mode="resource". The scenarios, tests and notebooks are full of it. Subclass str. This keeps all of that working unchanged. Mode.RESOURCE == "resource" is true. So is mode in (Mode.RESOURCE, Mode.WATCHDOG) for a caller who passed the bare string. The constant is the better way to say it. The string does not stop being a way to say it.

class kapps_semantic_middleware.modes.Mode(*values)

Bases: str, Enum

A middleware instance mode. Each member below says what it means.

RESOURCE = 'resource'

Wrap one resource_iri. Register a Service. Serve its workflows and parameters. Hold a heartbeat. This is the only mode with runtime consequence today.

SERVER = 'server'

Reserved. Serve data with no physical resource. Not implemented. Construct one raises. Out of scope for the scenario-3 controller: a controller consumes a graph, and it does not serve one.

WATCHDOG = 'watchdog'

Reserved. Sweep liveness from a central point. Sweep stale Services. Register nothing of its own.

kapps_semantic_middleware.modes.ALL = (Mode.RESOURCE, Mode.SERVER, Mode.WATCHDOG)

Every valid mode. Use for validation. Use for error messages that list the alternatives.