spi/me.ahoo.wow.spi.snapshot

Package-level declarations

Types

class RebuildSnapshot @InternalWowApi constructor(val ids: List<String>)

The system command wow.snapshot.Rebuild: rebuilds from the log the snapshots of the aggregates ids of one aggregate type, in the tenant of the instance it is sent to: the aggregate <context>.snapshot whose id is the name of that aggregate type. A snapshot written wrong is repaired this way; the rebuild runs in the background, once the request is committed.

SnapshotRebuildRequested

@InternalWowApi

class SnapshotRebuildRequested @InternalWowApi constructor(val ids: List<String>)

The system event wow.SnapshotRebuildRequested: the snapshots of the aggregates ids are to be rebuilt.

SnapshotRebuilds

@InternalWowApi

object SnapshotRebuilds

The names of the snapshot rebuild aggregate, its system command and event.

SnapshotRebuildStore

@WowSpi

interface SnapshotRebuildStore

The snapshot rebuild control plane of a SnapshotStore, its own port: a store offers it through SnapshotStore.rebuilds. The snapshot subscriptions never use it; the node's snapshot maintenance does.

SnapshotRecord

class SnapshotRecord @InternalWowApi constructor(val ref: AggregateRef, val version: Int, val schemaFingerprint: String, val state: String, val scope: Scope = Scope.NONE, val deleted: Boolean = false, val firstEventTime: Long, val lastEventTime: Long, val access: Map<String, Any?> = emptyMap(), val operator: Operator? = null, val firstOperator: Operator? = null, val schedules: Map<String, ScheduleRule> = emptyMap(), val stateRevision: Int = 1)

An aggregate's latest committed state as the snapshot store keeps it: a cache derived from the log, never a fact.

SnapshotSaveOutcome

@WowSpi

sealed interface SnapshotSaveOutcome

How the save of one snapshot of a SnapshotStore.saveAll ended: Written, Refused by the version guard (the store holds the same or a later version, or one of a higher state revision, which the save then marked stale), or Failed alone, the others of the batch unaffected. A failure of the whole call is thrown instead.

SnapshotStore

@WowSpi

interface SnapshotStore

The snapshots of one bounded context: each aggregate's latest committed state, the default read model (axiom A11, documentation/designs/03-log-and-snapshot.md §3). A snapshot is derived from the log and can be rebuilt from it, so it is written outside the append and a lost write costs only a rebuild.

SnapshotTable

class SnapshotTable @InternalWowApi constructor(val revision: Int, val rebuilding: Boolean = false, val backfilled: Boolean = true)

The record of one aggregate type's snapshot table: the state revision it is claimed at, whether snapshots of another revision or marked stale may remain to be rewritten (rebuilding), and whether the table has caught up with the log since it was first claimed (backfilled): a snapshot target added to a running service is filled from the beginning of the log. A query of a table that is catchingUp answers with rebuilding.