PuduLangLog.LevelSwitch

type: module path: "@root/src/PuduLangLog/LevelSwitch.pudu" fidelity: Active grammar: "[[grammar/pudu]]" depth_score: 0.5 depth_status: MEDIUM tags: [module] aliases: [PuduLangLog.LevelSwitch]

Purpose

A [[domain/Level|minimum level]] shared by loggers, sinks, and enrichers and changed while the program runs, with listeners told of each change.

Interface

Signatures

export type LevelSwitch = { current: Sync.Cell[Log.Level], lock: Sync.Mutex, listeners: Sync.Cell[Array[fn(Log.Level, Log.Level) -> ()]] }

export fn create(initial: Log.Level) -> LevelSwitch

export fn level(control: &LevelSwitch) -> Log.Level

export fn allows(control: &LevelSwitch, candidate: Log.Level) -> Bool

export fn set(control: &LevelSwitch, next: Log.Level) -> ()

export fn onChange(control: &LevelSwitch, listener: fn(Log.Level, Log.Level) -> ()) -> ()

Linkage

• Requires: [[src/PuduLangLog]], [[src/PuduLangLog/Domain/Levels]], Std.Sync.
• Consumed by: [[src/PuduLangLog/Configuration]], [[src/PuduLangLog/Pipeline]], [[src/PuduLangLog/Sink]], [[src/PuduLangLog/Enricher]], and settings.

Algorithm

1. The level lives in a cell; set compares and stores under the switch's lock.
2. When the level changed, every listener is called with the old and new levels after the lock is released.

Negative Logic (Prohibited Paths)

• Setting the level it already has calls no listener.

Edge Cases

• A listener that sets the switch again runs after the first change is stored, so no lock is held twice.

Depth

DEPTH 0.5 (MEDIUM). Tested by test/PuduLangLog/LoggerTest.

Grill Log

• Q: Why call listeners outside the lock? A: A listener may log or change the switch; holding the lock would deadlock it. _Rejected:_ calling inside the lock.

Referenced by

[[domain/Level]] · [[src/PuduLangLog/_MOC]] · [[src/PuduLangLog/Configuration]] · [[src/PuduLangLog/Enricher]] · [[src/PuduLangLog/Pipeline]] · [[src/PuduLangLog/Settings]] · [[src/PuduLangLog/Sink]]