src/coordinator/CoordinatorPolicy.bend

mylsm-lsm-store@0.6.0.1 · 133 lines · 11 definitions

1import Base
2
3# Represents the owner lifecycle around lock, recovery, endpoint, and shutdown.
4type State is Data:
5  Starting{}
6  Locked{}
7  Recovered{}
8  Serving{}
9  Stopping{}
10  EndpointRemoved{}
11  Closed{}
12  Failed{}
13
14# Represents one external result or requested lifecycle action.
15type OwnerEvent is Data:
16  AcquireLock{}
17  RecoveryComplete{}
18  PublishEndpoint{}
19  BeginShutdown{}
20  RemoveEndpoint{}
21  ReleaseLock{}
22  Failure{}
23
24# Returns the next legal state or rejects an out-of-order event.
25type Decision is Data:
26  Advance{state: State}
27  Reject{}
28
29# Classifies durable failures before mapping them into wire statuses.
30type FailureKind is Data:
31  BusyFailure{}
32  TimeoutFailure{}
33  NotFoundFailure{}
34  InvalidArgumentFailure{}
35  AlreadyExistsFailure{}
36  UnsupportedPlatformFailure{}
37  ResourceLimitFailure{}
38  CorruptionFailure{}
39  IoFailure{}
40  CommitUnknownFailure{}
41
42# Defines the typed response statuses available to coordinator clients.
43type ReplyStatus is Data:
44  SuccessStatus{}
45  InvalidArgumentStatus{}
46  AlreadyExistsStatus{}
47  UnsupportedPlatformStatus{}
48  NotFoundStatus{}
49  BusyStatus{}
50  TimeoutStatus{}
51  ResourceLimitStatus{}
52  CorruptionStatus{}
53  IoStatus{}
54  CommitUnknownStatus{}
55
56# Records whether the open path acquired, contended on, or failed to acquire the lock.
57type LockOutcome is Data:
58  LockAcquired{}
59  LockBusy{}
60  LockFailed{}
61
62# Records whether canonical endpoint inspection found a live candidate.
63type EndpointOutcome is Data:
64  EndpointPresent{}
65  EndpointMissing{}
66  EndpointFailed{}
67
68# Selects local ownership, remote use, or a typed open failure.
69type OpenRole is Data:
70  LocalOwner{}
71  ExistingOwnerClient{}
72  ReturnBusy{}
73  PropagateOpenFailure{}
74
75# Chooses local ownership or an established endpoint from lock observations.
76def open.role(lock: LockOutcome, endpoint: EndpointOutcome) -> OpenRole:
77  match lock:
78    case LockAcquired{}: LocalOwner{}
79    case LockBusy{}:
80      match endpoint:
81        case EndpointPresent{}: ExistingOwnerClient{}
82        case EndpointMissing{}: ReturnBusy{}
83        case EndpointFailed{}: PropagateOpenFailure{}
84    case LockFailed{}: PropagateOpenFailure{}
85
86def failure.status(kind: FailureKind) -> ReplyStatus:
87  match kind:
88    case BusyFailure{}: BusyStatus{}
89    case TimeoutFailure{}: TimeoutStatus{}
90    case NotFoundFailure{}: NotFoundStatus{}
91    case InvalidArgumentFailure{}: InvalidArgumentStatus{}
92    case AlreadyExistsFailure{}: AlreadyExistsStatus{}
93    case UnsupportedPlatformFailure{}: UnsupportedPlatformStatus{}
94    case ResourceLimitFailure{}: ResourceLimitStatus{}
95    case CorruptionFailure{}: CorruptionStatus{}
96    case IoFailure{}: IoStatus{}
97    case CommitUnknownFailure{}: CommitUnknownStatus{}
98
99# Applies one lifecycle event without performing host effects.
100def step(state: State, event: OwnerEvent) -> Decision:
101  match state:
102    case Starting{}:
103      match event:
104        case AcquireLock{}: Advance{Locked{}}
105        case Failure{}: Advance{Failed{}}
106        case _: Reject{}
107    case Locked{}:
108      match event:
109        case RecoveryComplete{}: Advance{Recovered{}}
110        case Failure{}: Advance{Failed{}}
111        case _: Reject{}
112    case Recovered{}:
113      match event:
114        case PublishEndpoint{}: Advance{Serving{}}
115        case Failure{}: Advance{Failed{}}
116        case _: Reject{}
117    case Serving{}:
118      match event:
119        case BeginShutdown{}: Advance{Stopping{}}
120        case Failure{}: Advance{Failed{}}
121        case _: Reject{}
122    case Stopping{}:
123      match event:
124        case RemoveEndpoint{}: Advance{EndpointRemoved{}}
125        case Failure{}: Advance{Failed{}}
126        case _: Reject{}
127    case EndpointRemoved{}:
128      match event:
129        case ReleaseLock{}: Advance{Closed{}}
130        case Failure{}: Advance{Failed{}}
131        case _: Reject{}
132    case Closed{}: Reject{}
133    case Failed{}: Reject{}