selene_graph/
shared_snapshot.rs

1//! Snapshot writing facade for [`SharedGraph`](crate::SharedGraph).
2
3use selene_persist::{SnapshotBuilder, SnapshotConfig, SnapshotFinalizeOutcome};
4
5use crate::{GraphResult, SharedGraph};
6
7impl SharedGraph {
8    /// Write one snapshot containing every registered provider section.
9    ///
10    /// This is the graph-layer facade over [`SnapshotBuilder`]. It walks the
11    /// fixed provider registry, asks each provider to encode every declared
12    /// subsection, and finalizes the snapshot envelope from `config`.
13    ///
14    /// Call after the commit whose state should be checkpointed has returned.
15    /// Callers that need a deterministic checkpoint should avoid concurrent
16    /// writes while this method is collecting provider sections.
17    ///
18    /// # Errors
19    ///
20    /// Returns [`crate::GraphError::Provider`] when a provider cannot encode one
21    /// of its declared sections, or [`crate::GraphError::Persist`] when the
22    /// snapshot envelope cannot be finalized.
23    pub fn write_snapshot(&self, config: SnapshotConfig) -> GraphResult<SnapshotFinalizeOutcome> {
24        let mut builder = SnapshotBuilder::new(config);
25        for provider in self.index_providers() {
26            let provider_tag = provider.provider_tag();
27            for sub_tag in provider.declared_sub_tags() {
28                let bytes = provider.write_section(*sub_tag)?;
29                builder.add_section(provider_tag.0, sub_tag.0, bytes)?;
30            }
31        }
32        builder.finalize().map_err(Into::into)
33    }
34}
35
36#[cfg(test)]
37mod tests {
38    use std::path::PathBuf;
39    use std::sync::Arc;
40    use std::time::{SystemTime, UNIX_EPOCH};
41
42    use selene_core::{Change, GraphId};
43    use selene_persist::{SectionCompression, SnapshotConfig, SnapshotReader, snapshot_path};
44
45    use crate::SharedGraph;
46    use crate::index_provider::{IndexProvider, ProviderError, ProviderTag, SubTag};
47
48    const TEST_PROVIDER: [u8; 4] = *b"TST1";
49    const TEST_SUB: [u8; 4] = *b"BODY";
50    const TEST_SUB_TAGS: &[SubTag] = &[SubTag(TEST_SUB)];
51
52    struct SnapshotOnlyProvider;
53
54    impl IndexProvider for SnapshotOnlyProvider {
55        fn provider_tag(&self) -> ProviderTag {
56            ProviderTag(TEST_PROVIDER)
57        }
58
59        fn read_section(&self, _sub_tag: SubTag, _bytes: &[u8]) -> Result<(), ProviderError> {
60            Ok(())
61        }
62
63        fn write_section(&self, sub_tag: SubTag) -> Result<Vec<u8>, ProviderError> {
64            assert_eq!(sub_tag, SubTag(TEST_SUB));
65            Ok(b"provider-body".to_vec())
66        }
67
68        fn on_change(&self, _change: &Change) -> Result<(), ProviderError> {
69            Ok(())
70        }
71
72        fn declared_sub_tags(&self) -> &[SubTag] {
73            TEST_SUB_TAGS
74        }
75    }
76
77    #[test]
78    fn write_snapshot_includes_registered_provider_sections() {
79        let dir = temp_dir("shared-snapshot");
80        let provider = Arc::new(SnapshotOnlyProvider);
81        let shared = SharedGraph::builder(GraphId::new(82_001))
82            .with_provider(provider as Arc<dyn IndexProvider>)
83            .build()
84            .unwrap();
85
86        let outcome = shared
87            .write_snapshot(SnapshotConfig {
88                dir: dir.clone(),
89                sequence: 7,
90                compression: SectionCompression::None,
91                fsync: false,
92            })
93            .unwrap();
94
95        assert_eq!(outcome.snapshot_seq, 7);
96        assert!(outcome.section_count > 1);
97        let mut reader = SnapshotReader::open(&snapshot_path(&dir, 7)).unwrap();
98        assert_eq!(
99            reader.read_section(TEST_PROVIDER, TEST_SUB).unwrap(),
100            b"provider-body"
101        );
102    }
103
104    fn temp_dir(name: &str) -> PathBuf {
105        let nanos = SystemTime::now()
106            .duration_since(UNIX_EPOCH)
107            .unwrap()
108            .as_nanos();
109        let dir = std::env::temp_dir().join(format!(
110            "selene-graph-{name}-{}-{nanos}",
111            std::process::id()
112        ));
113        let _ = std::fs::remove_dir_all(&dir);
114        std::fs::create_dir(&dir).unwrap();
115        dir
116    }
117}
selene_graph/shared_snapshot.rs

selene_graph/
shared_snapshot.rs
