State Graph

The state graph models explicit, versioned state for kernel ticks. Each commit creates a new StateNodeId derived from the state bytes, parent nodes, and metadata. A SnapshotPolicy determines when snapshots are created.

SnapshotPolicy

Fields

• interval (Option<u64>): snapshot every N ticks when set.
• important_labels (Vec<String>): labels that always trigger snapshots.

Behavior

• Snapshot when tick % interval == 0 (for interval > 0).
• Snapshot when StateMetadata.label matches any important_labels entry.

StateGraph

Fields

• store (Arc<dyn StateStore>): backing persistence layer.
• head (Option<StateNodeId>): current head node.
• tick (u64): commit counter.
• policy (SnapshotPolicy): snapshot policy applied at commit time.

Commit sequence

1. Persist StateData via StateStore::put_state.
2. Record node using StateStore::commit_node with the current head as parent.
3. Increment tick and evaluate SnapshotPolicy.
4. Optionally create a snapshot via StateStore::snapshot.

StateCommit

Fields

• node_id (StateNodeId): identifier of the committed node.
• snapshot_id (Option<SnapshotId>): snapshot identifier when created.

StateGraphError

StateGraphError::Store wraps StateStoreError failures.

Example

use splendor_kernel::{SnapshotPolicy, StateGraph};
use splendor_store::{InMemoryStateStore, StateData, StateMetadata};
use std::sync::Arc;
use time::OffsetDateTime;

let store = Arc::new(InMemoryStateStore::default());
let policy = SnapshotPolicy { interval: Some(2), important_labels: vec![] };
let mut graph = StateGraph::new(store, policy);
let data = StateData { bytes: vec![1], content_type: None };
let metadata = StateMetadata { created_at: OffsetDateTime::now_utc(), label: None };
let commit = graph.commit(data, metadata).expect("commit");
assert_eq!(graph.head(), Some(&commit.node_id));