src/DurableDbPolicy.bend source

src/DurableDbPolicy.bend on the hub · documented module

import Baseimport ./DurableError.bend as DurableError# Tracks whether the handle accepts data operations.type HandleState is Data:  Open{}  Poisoned{}  MaintenanceBlocked{}# Increments the per-handle operation error count.def next_operation_errors(count: Nat) -> Nat:  Nat.add(count, 1n)# Distinguishes failures before and after WAL append begins.type AppendPhase is Data:  BeforeAppend{}  AppendStarted{}# Tracks whether failed maintenance blocks later writes.type MaintenanceState is Data:  MaintenanceSucceeded{}  MaintenanceFailed{error: DurableError.Error}# Checks whether accepts data operation.def accepts_data_operation(state: HandleState) -> Bool:  match state:    case Open{}:      True{}    case Poisoned{}:      False{}    case MaintenanceBlocked{}:      False{}# Selects handle state from the write failure stage.def state_after_write_failure(phase: AppendPhase, current: HandleState) -> HandleState:  match phase:    case BeforeAppend{}:      current    case AppendStarted{}:      Poisoned{}# Blocks writes when maintenance fails.def state_after_maintenance(result: MaintenanceState) -> HandleState:  match result:    case MaintenanceSucceeded{}:      Open{}    case MaintenanceFailed{_}:      MaintenanceBlocked{}# Reports maintenance separately from the confirmed commit.def committed_maintenance(commit_error: Maybe<&2, DurableError.Error>) -> Bool:  match commit_error:    case Some{_}:      False{}    case None{}:      True{}