kuilt-raft/us.tractat.kuilt.raft/DurableStoreRaftStorage

DurableStoreRaftStorage

class DurableStoreRaftStorage : RaftStorage

A RaftStorage that keeps a node's term, vote, established leader, log and snapshot in a DurableStore, so they are all still there after the process restarts.

This is the reference durable adapter — the answer to the "inject a persistent RaftStorage in production" line every other doc in this module points at. Give it whichever DurableStore the platform provides (FileChannelDurableStore on JVM/Android, NSFileManagerDurableStore on iOS/macOS, IndexedDbDurableStore in a browser) and the node comes back holding what it knew:

val storage = DurableStoreRaftStorage.open(FileChannelDurableStore(nodeDirectory))
val node = scope.raftNode(cluster, transport, storage)

Samples

// One store per node. In production this is the platform's crash-safe implementation —
// FileChannelDurableStore(nodeDirectory), NSFileManagerDurableStore(nodeDirectory), or
// IndexedDbDurableStore.open(nodeDatabase). A sample uses the in-memory one.
val store: DurableStore = InMemoryDurableStore()

val storage = DurableStoreRaftStorage.open(store)

// Every mutator commits to the medium before it updates its own memory, so a term that has
// been saved is a term that survives — pass this to `scope.raftNode(cluster, transport, storage)`.
storage.saveTermAndVotedFor(term = 4L, votedFor = NodeId("node-a"))
storage.appendEntries(listOf(LogEntry(index = 1L, term = 4L, command = byteArrayOf(7, 8, 9))))

// A restart: a second handle onto the same store, decoding what the first one wrote.
val restarted = DurableStoreRaftStorage.open(store)
check(restarted.term() == 4L)
check(restarted.votedFor() == NodeId("node-a"))
check(restarted.entries().single().command.contentEquals(byteArrayOf(7, 8, 9)))