fakecloud_appsync/
persistence.rs

1//! Snapshot save/load for AWS AppSync state.
2
3use std::sync::Arc;
4
5use tokio::sync::Mutex as AsyncMutex;
6
7use fakecloud_persistence::SnapshotStore;
8
9use crate::state::{AppSyncSnapshot, SharedAppSyncState, APPSYNC_SNAPSHOT_SCHEMA_VERSION};
10
11#[derive(Debug, PartialEq, Eq)]
12pub enum LoadOutcome {
13    Empty,
14    Loaded(usize),
15}
16
17#[derive(Debug, thiserror::Error)]
18pub enum LoadError {
19    #[error("failed to read appsync persistence snapshot: {0}")]
20    Io(String),
21    #[error("failed to parse appsync persistence snapshot: {0}")]
22    Parse(String),
23    #[error("appsync persistence schema too new: on-disk={on_disk}, max supported={supported}")]
24    SchemaTooNew { on_disk: u32, supported: u32 },
25}
26
27pub fn load_into(
28    store: &dyn SnapshotStore,
29    state: &SharedAppSyncState,
30) -> Result<LoadOutcome, LoadError> {
31    let Some(bytes) = store.load().map_err(|e| LoadError::Io(e.to_string()))? else {
32        return Ok(LoadOutcome::Empty);
33    };
34    let snapshot: AppSyncSnapshot =
35        serde_json::from_slice(&bytes).map_err(|e| LoadError::Parse(e.to_string()))?;
36    if snapshot.schema_version > APPSYNC_SNAPSHOT_SCHEMA_VERSION {
37        return Err(LoadError::SchemaTooNew {
38            on_disk: snapshot.schema_version,
39            supported: APPSYNC_SNAPSHOT_SCHEMA_VERSION,
40        });
41    }
42    let accounts = snapshot.accounts.account_count();
43    *state.write() = snapshot.accounts;
44    Ok(LoadOutcome::Loaded(accounts))
45}
46
47pub async fn save_snapshot(
48    state: &SharedAppSyncState,
49    store: Option<Arc<dyn SnapshotStore>>,
50    lock: &AsyncMutex<()>,
51) {
52    let Some(store) = store else {
53        return;
54    };
55    let _guard = lock.lock().await;
56    let snapshot = AppSyncSnapshot {
57        schema_version: APPSYNC_SNAPSHOT_SCHEMA_VERSION,
58        accounts: state.read().clone(),
59    };
60    let join = tokio::task::spawn_blocking(move || -> std::io::Result<()> {
61        let bytes = serde_json::to_vec(&snapshot)
62            .map_err(|e| std::io::Error::new(std::io::ErrorKind::InvalidData, e.to_string()))?;
63        store.save(&bytes)
64    })
65    .await;
66    match join {
67        Ok(Ok(())) => {}
68        Ok(Err(err)) => tracing::error!(%err, "failed to write appsync snapshot"),
69        Err(err) => tracing::error!(%err, "appsync snapshot task panicked"),
70    }
71}
72
73#[cfg(test)]
74mod tests {
75    use super::*;
76    use crate::state::AppSyncData;
77    use fakecloud_core::multi_account::MultiAccountState;
78    use parking_lot::RwLock;
79    use serde_json::json;
80    use std::sync::Mutex;
81
82    struct MemStore(Mutex<Option<Vec<u8>>>);
83    impl SnapshotStore for MemStore {
84        fn load(&self) -> std::io::Result<Option<Vec<u8>>> {
85            Ok(self.0.lock().unwrap().clone())
86        }
87        fn save(&self, bytes: &[u8]) -> std::io::Result<()> {
88            *self.0.lock().unwrap() = Some(bytes.to_vec());
89            Ok(())
90        }
91    }
92
93    fn state() -> SharedAppSyncState {
94        Arc::new(RwLock::new(MultiAccountState::new(
95            "000000000000",
96            "us-east-1",
97            "",
98        )))
99    }
100
101    #[test]
102    fn empty_store_is_empty() {
103        assert_eq!(
104            load_into(&MemStore(Mutex::new(None)), &state()).unwrap(),
105            LoadOutcome::Empty
106        );
107    }
108
109    #[test]
110    fn round_trip_restores_apis() {
111        let mut accounts: MultiAccountState<AppSyncData> =
112            MultiAccountState::new("000000000000", "us-east-1", "");
113        let data = accounts.get_or_create("111122223333");
114        data.graphql_apis
115            .insert("abc".to_string(), json!({ "apiId": "abc", "name": "demo" }));
116        let snap = AppSyncSnapshot {
117            schema_version: APPSYNC_SNAPSHOT_SCHEMA_VERSION,
118            accounts,
119        };
120        let store = MemStore(Mutex::new(Some(serde_json::to_vec(&snap).unwrap())));
121        let restored = state();
122        assert_eq!(
123            load_into(&store, &restored).unwrap(),
124            LoadOutcome::Loaded(2)
125        );
126        let guard = restored.read();
127        assert!(guard
128            .get("111122223333")
129            .unwrap()
130            .graphql_apis
131            .contains_key("abc"));
132    }
133
134    #[test]
135    fn rejects_future_schema() {
136        let accounts: MultiAccountState<AppSyncData> =
137            MultiAccountState::new("000000000000", "us-east-1", "");
138        let bytes = serde_json::to_vec(&serde_json::json!({
139            "schema_version": APPSYNC_SNAPSHOT_SCHEMA_VERSION + 1,
140            "accounts": accounts,
141        }))
142        .unwrap();
143        let store = MemStore(Mutex::new(Some(bytes)));
144        assert!(matches!(
145            load_into(&store, &state()),
146            Err(LoadError::SchemaTooNew { .. })
147        ));
148    }
149}
fakecloud_appsync/persistence.rs

fakecloud_appsync/
persistence.rs
