exoware_server/
engine.rs

1//! Storage callbacks for the store services.
2//!
3//! Implement this trait for your backend. Errors are surfaced to clients as internal RPC failures
4//! (string message only; keep messages safe to expose if you rely on that).
5
6use bytes::Bytes;
7
8/// Implement these operations for your store. All methods must be thread-safe.
9pub trait StoreEngine: Send + Sync + 'static {
10    /// Persist key-value pairs atomically and return the new global sequence number for this write.
11    fn put_batch(&self, kvs: &[(Bytes, Bytes)]) -> Result<u64, String>;
12
13    /// Fetch the value for a single key. Returns `None` when the key does not exist.
14    fn get(&self, key: &[u8]) -> Result<Option<Vec<u8>>, String>;
15
16    /// Keys in `[start, end]` (inclusive) when `end` is non-empty; empty `end` means unbounded
17    /// above. Matches `store.query.v1.RangeRequest` / `ReduceRequest` on the wire. `limit` caps
18    /// rows returned.
19    fn range_scan(
20        &self,
21        start: &[u8],
22        end: &[u8],
23        limit: usize,
24        forward: bool,
25    ) -> Result<Vec<(Bytes, Bytes)>, String>;
26
27    /// Batch-get: returns `(key, Option<value>)` for each input key, preserving order.
28    fn get_many(&self, keys: &[&[u8]]) -> Result<Vec<(Vec<u8>, Option<Vec<u8>>)>, String> {
29        keys.iter()
30            .map(|k| Ok((k.to_vec(), self.get(k)?)))
31            .collect()
32    }
33
34    /// Delete a batch of keys atomically. Returns the new global sequence number.
35    fn delete_batch(&self, keys: &[&[u8]]) -> Result<u64, String>;
36
37    /// Current sequence number visible to readers (used for `min_sequence_number` checks).
38    fn current_sequence(&self) -> u64;
39
40    /// Return the (key, value) pairs written by the `put_batch` call that was
41    /// assigned `sequence_number`. `Ok(None)` = the batch has been pruned or
42    /// was never written (the store.stream.v1 service maps `None` to NOT_FOUND
43    /// with a `BATCH_EVICTED` detail).
44    ///
45    /// Engines that don't retain a batch log return `Ok(None)` unconditionally,
46    /// which disables `GetBatch` and since-cursored `Subscribe` for that
47    /// deployment.
48    fn get_batch(&self, sequence_number: u64) -> Result<Option<Vec<(Bytes, Bytes)>>, String>;
49
50    /// Lowest retained batch sequence number, or `None` when the batch log is
51    /// empty. Surfaced in `BATCH_EVICTED` error details so clients know where
52    /// to resume from.
53    fn oldest_retained_batch(&self) -> Result<Option<u64>, String>;
54
55    /// Delete all batch-log entries with `sequence_number < cutoff_exclusive`.
56    /// Returns the number of entries deleted. Invoked only by the compact
57    /// service's batch-log policy scope — never by ingest.
58    fn prune_batch_log(&self, cutoff_exclusive: u64) -> Result<u64, String>;
59}
exoware_server/engine.rs

exoware_server/
engine.rs
