a bit of doc, stub cache impl

3 files changed, 77 insertions, 0 deletions

diff --git a/src/modules/cache.rs b/src/modules/cache.rs
new file mode 100644
index 0000000..d306ed1
--- /dev/null
+++ b/src/modules/cache.rs
@@ -0,0 +1,72 @@
+//! Response caching module
+//!
+//! Considerations:
+//! - check cache header
+//! - ignore responses that get too large
+//! - ignore requests with body (or too large body)
+//! - LRU cache pruning
+//! - different backends:
+//!     - in memory (HashMap)
+//!     - on disk (redb? filesystem?)
+//!     - external db?
+use super::{Node, NodeContext, NodeKind, NodeRequest, NodeResponse};
+use crate::{config::DynNode, error::ServiceError};
+use anyhow::Result;
+use bytes::Bytes;
+use http::Response;
+use http_body_util::BodyExt;
+use serde::Deserialize;
+use serde_yaml::Value;
+use sha2::{Digest, Sha256};
+use std::{collections::HashMap, future::Future, pin::Pin, sync::Arc};
+
+pub struct CacheKind;
+
+#[derive(Deserialize)]
+struct CacheConfig {
+    next: DynNode,
+}
+
+struct Cache {
+    entries: HashMap<[u8; 32], Response<Bytes>>,
+    config: CacheConfig,
+}
+
+impl NodeKind for CacheKind {
+    fn name(&self) -> &'static str {
+        "cache"
+    }
+    fn instanciate(&self, config: Value) -> Result<Arc<dyn Node>> {
+        let config = serde_yaml::from_value::<CacheConfig>(config)?;
+        Ok(Arc::new(Cache {
+            config,
+            entries: HashMap::new(),
+        }))
+    }
+}
+impl Node for Cache {
+    fn handle<'a>(
+        &'a self,
+        context: &'a mut NodeContext,
+        request: NodeRequest,
+    ) -> Pin<Box<dyn Future<Output = Result<NodeResponse, ServiceError>> + Send + Sync + 'a>> {
+        Box::pin(async move {
+            // totally wrong...
+            let mut hasher = Sha256::new();
+            hasher.update(request.method().as_str());
+            hasher.update(request.uri().path());
+            if let Some(q) = request.uri().query() {
+                hasher.update(q);
+            }
+            let key: [u8; 32] = hasher.finalize().try_into().unwrap();
+
+            if let Some(resp) = self.entries.get(&key) {
+                // Ok(resp.to_owned().map(|b| b.map_err(|e| match e {}).boxed()))
+            }
+
+            let response = self.config.next.handle(context, request).await?;
+
+            Ok(response)
+        })
+    }
+}
diff --git a/src/modules/loadbalance.rs b/src/modules/loadbalance.rs
index 168db33..5358b03 100644
--- a/src/modules/loadbalance.rs
+++ b/src/modules/loadbalance.rs
@@ -1,3 +1,7 @@
+//! Load balancing module
+//!
+//! Given a set of handlers, the handler that is the least busy will handle the next request.
+//! Current implementation does not scale well for many handlers.
 use super::{Node, NodeContext, NodeKind, NodeRequest, NodeResponse};
 use crate::{config::DynNode, error::ServiceError};
 use anyhow::Result;
diff --git a/src/modules/mod.rs b/src/modules/mod.rs
index e0f74ec..2494771 100644
--- a/src/modules/mod.rs
+++ b/src/modules/mod.rs
@@ -21,6 +21,7 @@ pub mod proxy;
 pub mod redirect;
 pub mod switch;
 pub mod loadbalance;
+pub mod cache;
 
 pub type NodeRequest = Request<Incoming>;
 pub type NodeResponse = Response<BoxBody<Bytes, ServiceError>>;