harn-stdlib 0.10.47

Embedded Harn standard library source catalog
Documentation 
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/** Portable, read-only ambient host-condition observations. */
pub type HostContentionQuestion = "promised_cpu" \
  | "nominal_speed" \
  | "accelerator_shared" \
  | "memory_or_io_contended"

pub type HostEnvironment = "bare_metal" | "virtualized" | "containerized" | "unknown"

pub type HostConditionObserved = {
  question: HostContentionQuestion,
  status: "observed",
  contention: float,
  reason?: string,
}

pub type HostConditionUnavailable = {
  question: HostContentionQuestion,
  status: "unavailable",
  contention?: float,
  reason: string,
}

pub type HostConditionNotObservable = {
  question: HostContentionQuestion,
  status: "not_observable",
  contention?: float,
  reason: string,
}

pub type HostConditionObservation = HostConditionObserved \
  | HostConditionUnavailable \
  | HostConditionNotObservable

pub type HostConditionsSnapshot = {
  schema_version: int,
  observed_at_ms: int,
  environment: HostEnvironment,
  sample_cost_us: int,
  questions: list<HostConditionObservation>,
}

/**
 * Sample ambient host contention without acquiring or mutating anything.
 *
 * A contention value of zero is a genuinely observed quiet reading. Missing
 * facts stay distinguishable as `unavailable` (retryable read failure) or
 * `not_observable` (structural environment limit).
 *
 * Randomized assignment plus blocking on host is the correctness guarantee
 * for comparisons. These readings only avoid waste and attribute suspicious
 * results; they never substitute for randomized assignment.
 *
 * @effects: [host]
 * @errors: [backend_error, invalid_parameter, missing_parameter]
 */
pub fn host_conditions_sample() -> HostConditionsSnapshot {
  return hostlib_host_conditions_sample({schema_version: 1})
}