tower_resilience_cache/
layer.rs

1use crate::{Cache, CacheConfig};
2use std::hash::Hash;
3use std::sync::Arc;
4use tower::Layer;
5
6/// A Tower [`Layer`] that applies response caching to a service.
7///
8/// This layer wraps a service with a [`Cache`] middleware that stores
9/// successful responses and returns cached values for subsequent requests
10/// with the same key.
11///
12/// # State Isolation
13///
14/// **Note:** Each call to [`layer()`](Layer::layer) creates a new cache store.
15/// If you need multiple services to share the same cache (e.g., when using a
16/// `ServiceFactory` that creates per-session services), use
17/// [`SharedCacheLayer`](crate::SharedCacheLayer) instead, or call
18/// [`.shared()`](CacheLayer::shared) on this layer.
19///
20/// # Examples
21///
22/// ```
23/// use tower_resilience_cache::CacheLayer;
24/// use tower::ServiceBuilder;
25/// use std::time::Duration;
26///
27/// # async fn example() {
28/// let cache_layer = CacheLayer::builder()
29///     .max_size(100)
30///     .ttl(Duration::from_secs(60))
31///     .key_extractor(|req: &String| req.clone())
32///     .build()
33///     .unwrap();
34///
35/// let service = ServiceBuilder::new()
36///     .layer(cache_layer)
37///     .service(my_service());
38/// # }
39/// # fn my_service() -> impl tower::Service<String, Response = String, Error = std::io::Error> {
40/// #     tower::service_fn(|req: String| async move { Ok::<_, std::io::Error>(req) })
41/// # }
42/// ```
43#[derive(Clone)]
44pub struct CacheLayer<Req, K> {
45    config: Arc<CacheConfig<Req, K>>,
46}
47
48impl<Req, K> CacheLayer<Req, K>
49where
50    K: Hash + Eq + Clone + Send + 'static,
51{
52    /// Creates a new `CacheLayer` with the given configuration.
53    pub fn new(config: CacheConfig<Req, K>) -> Self {
54        Self {
55            config: Arc::new(config),
56        }
57    }
58
59    /// Creates a new builder for configuring a cache layer.
60    ///
61    /// # Examples
62    ///
63    /// ```
64    /// use tower_resilience_cache::CacheLayer;
65    /// use std::time::Duration;
66    ///
67    /// let layer = CacheLayer::builder()
68    ///     .max_size(100)
69    ///     .ttl(Duration::from_secs(60))
70    ///     .key_extractor(|req: &String| req.clone())
71    ///     .build()
72    ///     .unwrap();
73    /// ```
74    pub fn builder() -> crate::CacheConfigBuilder<Req, K> {
75        crate::CacheConfigBuilder::new()
76    }
77
78    /// Converts this cache layer into a [`SharedCacheLayer`](crate::SharedCacheLayer) that shares
79    /// the cache store across all services created via [`layer()`](Layer::layer).
80    ///
81    /// This is useful when multiple service instances need to share the same cache,
82    /// such as when services are created per-session or per-request.
83    ///
84    /// # Type Parameters
85    ///
86    /// - `Resp`: The response type that will be cached. This must match the
87    ///   `Response` type of any service this layer is applied to.
88    ///
89    /// # Examples
90    ///
91    /// ```
92    /// use tower_resilience_cache::CacheLayer;
93    /// use tower::ServiceBuilder;
94    /// use std::time::Duration;
95    ///
96    /// # async fn example() {
97    /// let shared_cache = CacheLayer::builder()
98    ///     .max_size(100)
99    ///     .ttl(Duration::from_secs(60))
100    ///     .key_extractor(|req: &String| req.clone())
101    ///     .build()
102    ///     .unwrap()
103    ///     .shared::<String>();  // Specify the response type
104    ///
105    /// // Both services share the same cache
106    /// let service1 = ServiceBuilder::new()
107    ///     .layer(shared_cache.clone())
108    ///     .service(my_service());
109    ///
110    /// let service2 = ServiceBuilder::new()
111    ///     .layer(shared_cache)
112    ///     .service(my_service());
113    /// # }
114    /// # fn my_service() -> impl tower::Service<String, Response = String, Error = std::io::Error> {
115    /// #     tower::service_fn(|req: String| async move { Ok::<_, std::io::Error>(req) })
116    /// # }
117    /// ```
118    pub fn shared<Resp>(self) -> crate::shared_layer::SharedCacheLayer<Req, K, Resp>
119    where
120        Resp: Clone + Send + 'static,
121    {
122        crate::shared_layer::SharedCacheLayer::from_config(self.config)
123    }
124}
125
126impl<S, Req, K> Layer<S> for CacheLayer<Req, K>
127where
128    K: Hash + Eq + Clone + Send + 'static,
129    S: tower::Service<Req>,
130    S::Response: Clone + Send + 'static,
131{
132    type Service = Cache<S, Req, K, S::Response>;
133
134    fn layer(&self, service: S) -> Self::Service {
135        Cache::new(service, Arc::clone(&self.config))
136    }
137}
tower_resilience_cache/layer.rs

tower_resilience_cache/
layer.rs
