durable_session

Durable cluster-session contracts and ownership fencing for M27.

Types

ContinuityReport

Reconnect continuity measurements used for SLO checks.

pub type ContinuityReport {
  ContinuityReport(
    reconnect_latency_ms: Int,
    estimated_data_loss_events: Int,
    met: Bool,
  )
}

Constructors

ContinuityReport(
  reconnect_latency_ms: Int,
  estimated_data_loss_events: Int,
  met: Bool,
)

DurableSession

Durable session state tracked by the failover certification harness.

pub type DurableSession {
  DurableSession(
    backend: PersistenceBackend,
    resume_policy: ResumePolicy,
    fence: OwnershipFence,
    snapshot: Snapshot,
    journal_rev: List(JournalEntry),
    continuity_slo_ms: Int,
    max_data_loss_events: Int,
  )
}

Constructors

DurableSession(
  backend: PersistenceBackend,
  resume_policy: ResumePolicy,
  fence: OwnershipFence,
  snapshot: Snapshot,
  journal_rev: List(JournalEntry),
  continuity_slo_ms: Int,
  max_data_loss_events: Int,
)

JournalEntry

Journal entries persisted for replay and diagnostics.

pub type JournalEntry {
  CounterDelta(delta: Int)
  CrashMarked(reason: String)
  Restarted(now_ms: Int)
  Reconnected(policy: ResumePolicy, route: String, now_ms: Int)
}

Constructors

```
CounterDelta(delta: Int)
```
```
CrashMarked(reason: String)
```
```
Restarted(now_ms: Int)
```

Reconnected(policy: ResumePolicy, route: String, now_ms: Int)

LifecycleState

Durable lifecycle checkpoint labels.

pub type LifecycleState {
  Live
  Disconnected
  Crashed
}

Constructors

```
Live
```
```
Disconnected
```
```
Crashed
```

OwnershipError

Ownership claim rejection reasons.

pub type OwnershipError {
  StaleOwner(current_epoch: Int, requested_epoch: Int)
  SplitBrain(
    current_owner: String,
    requested_owner: String,
    epoch: Int,
  )
  InvalidToken(owner: String, epoch: Int)
}

Constructors

StaleOwner(current_epoch: Int, requested_epoch: Int)

SplitBrain(
  current_owner: String,
  requested_owner: String,
  epoch: Int,
)

```
InvalidToken(owner: String, epoch: Int)
```

OwnershipFence

Ownership fence used to reject stale owners.

pub type OwnershipFence {
  OwnershipFence(owner: String, epoch: Int, token: String)
}

Constructors

OwnershipFence(owner: String, epoch: Int, token: String)

PersistenceBackend

Persistence profile used by one durable session.

pub type PersistenceBackend {
  SnapshotOnly(store: String, checkpoint_every: Int)
  JournalOnly(store: String)
  SnapshotJournal(
    snapshot_store: String,
    journal_store: String,
    checkpoint_every: Int,
  )
}

Constructors

SnapshotOnly(store: String, checkpoint_every: Int)

```
JournalOnly(store: String)
```

SnapshotJournal(
  snapshot_store: String,
  journal_store: String,
  checkpoint_every: Int,
)

ResumePolicy

Reconnect policy for multi-node failover recovery.

pub type ResumePolicy {
  Resume
  Rehydrate
  Remount
}

Constructors

```
Resume
```
```
Rehydrate
```
```
Remount
```

Snapshot

Snapshot persisted for failover recovery.

pub type Snapshot {
  Snapshot(
    session_id: String,
    route: String,
    counter: Int,
    lifecycle: LifecycleState,
    checkpoint_epoch: Int,
    checkpoint_ms: Int,
  )
}

Constructors

Snapshot(
  session_id: String,
  route: String,
  counter: Int,
  lifecycle: LifecycleState,
  checkpoint_epoch: Int,
  checkpoint_ms: Int,
)

Values

append_counter_delta

pub fn append_counter_delta(
  session: DurableSession,
  delta: Int,
  now_ms: Int,
) -> DurableSession

Append one counter-delta entry and update the snapshot.

backend

pub fn backend(session: DurableSession) -> PersistenceBackend

Durable-state backend accessor.

backend_label

pub fn backend_label(backend: PersistenceBackend) -> String

Backend label.

continuity_report

pub fn continuity_report(
  session: DurableSession,
  failover_at_ms: Int,
  reconnect_at_ms: Int,
) -> ContinuityReport

Deterministic continuity SLO report for one failover timeline.

continuity_signature

pub fn continuity_signature(report: ContinuityReport) -> String

Continuity-report signature.

crash

pub fn crash(
  session: DurableSession,
  reason: String,
) -> DurableSession

Mark a crash in snapshot + journal.

expected_token

pub fn expected_token(
  session_id: String,
  owner: String,
  epoch: Int,
) -> String

Expected deterministic fence token.

fence

pub fn fence(session: DurableSession) -> OwnershipFence

Durable-state fence accessor.

fence_signature

pub fn fence_signature(fence: OwnershipFence) -> String

Ownership-fence signature.

journal

pub fn journal(session: DurableSession) -> List(JournalEntry)

Journal entries in append order.

journal_entry_label

pub fn journal_entry_label(entry: JournalEntry) -> String

Journal entry label.

lifecycle_label

pub fn lifecycle_label(lifecycle: LifecycleState) -> String

Lifecycle label.

ownership_error_label

pub fn ownership_error_label(error: OwnershipError) -> String

Ownership error label.

reconnect

pub fn reconnect(
  session: DurableSession,
  policy: ResumePolicy,
  route: String,
  now_ms: Int,
) -> DurableSession

Reconnect using one recovery policy.

request_takeover

pub fn request_takeover(
  session: DurableSession,
  owner: String,
  epoch: Int,
  token: String,
  now_ms: Int,
) -> Result(DurableSession, OwnershipError)

Attempt ownership takeover under fencing rules.

restart

pub fn restart(
  session: DurableSession,
  now_ms: Int,
) -> DurableSession

Mark a restart in snapshot + journal.

resume_policy_label

pub fn resume_policy_label(policy: ResumePolicy) -> String

Resume policy label.

signature

pub fn signature(session: DurableSession) -> String

Deterministic durable-session signature.

snapshot

pub fn snapshot(session: DurableSession) -> Snapshot

Durable-state snapshot accessor.

snapshot_signature

pub fn snapshot_signature(snapshot: Snapshot) -> String

Snapshot signature.

start

pub fn start(
  session_id: String,
  owner: String,
  route: String,
  backend: PersistenceBackend,
  resume_policy: ResumePolicy,
  now_ms: Int,
  continuity_slo_ms: Int,
  max_data_loss_events: Int,
) -> DurableSession

Start a durable session contract.

supported_backends

pub fn supported_backends() -> List(PersistenceBackend)

Supported backend matrix for M27 certification.

valid

pub fn valid(session: DurableSession) -> Bool

Validate one durable-session contract.