valence_core/
router.rs

1//! Named backend registry (heterogeneous engines per router).
2//!
3//! One [`DatabaseRouter`] per [`crate::Valence`]:
4//! - [`DatabaseRouter::register`] at build time (or inject via [`crate::ValenceBuilder::database_router`])
5//! - [`DatabaseRouter::resolve`] per operation / evaluator hop
6//!
7//! Cross-storage semantics:
8//! - Per-table `database:` evaluator → compound [`crate::router_key()`] → backend
9//! - Batch operations stay on a **single** backend
10//! - **No** cross-backend transactions
11
12use crate::backend::DatabaseBackend;
13use crate::error::{Error, Result};
14use std::collections::HashMap;
15use std::sync::{Arc, RwLock};
16
17/// Maps compound router keys to concrete [`DatabaseBackend`] implementations.
18///
19/// Keys look like `inmemory_mem:default` or `acme_vault:billing` — see [`crate::router_key()`].
20///
21/// # Examples
22///
23/// ```
24/// use std::sync::Arc;
25/// use valence_backend_mem::{InMemoryBackend, ENGINE_ID};
26/// use valence_core::{router_key, DatabaseRouter};
27///
28/// let mut router = DatabaseRouter::new();
29/// let key = router_key("default", ENGINE_ID);
30/// router.register(key.clone(), Arc::new(InMemoryBackend::new()));
31/// assert_eq!(router.resolve(&key).unwrap().engine_id(), ENGINE_ID);
32/// ```
33#[derive(Debug, Default)]
34pub struct DatabaseRouter {
35    backends: RwLock<HashMap<String, Arc<dyn DatabaseBackend>>>,
36}
37
38impl DatabaseRouter {
39    pub fn new() -> Self {
40        Self::default()
41    }
42
43    pub fn register(&mut self, key: impl Into<String>, backend: Arc<dyn DatabaseBackend>) {
44        self.backends
45            .get_mut()
46            .expect("router lock not poisoned")
47            .insert(key.into(), backend);
48    }
49
50    pub fn register_runtime(
51        &self,
52        key: impl Into<String>,
53        backend: Arc<dyn DatabaseBackend>,
54    ) -> Result<()> {
55        self.backends
56            .write()
57            .map_err(|_| Error::Internal("router lock poisoned".into()))?
58            .insert(key.into(), backend);
59        Ok(())
60    }
61
62    pub fn resolve(&self, key: &str) -> Result<Arc<dyn DatabaseBackend>> {
63        self.backends
64            .read()
65            .map_err(|_| Error::Internal("router lock poisoned".into()))?
66            .get(key)
67            .cloned()
68            .ok_or_else(|| Error::Internal(format!("unknown database backend: {key}")))
69    }
70
71    pub fn len(&self) -> Result<usize> {
72        Ok(self
73            .backends
74            .read()
75            .map_err(|_| Error::Internal("router lock poisoned".into()))?
76            .len())
77    }
78
79    pub fn is_empty(&self) -> Result<bool> {
80        Ok(self.len()? == 0)
81    }
82}
valence_core/router.rs

valence_core/
router.rs
