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|
//! 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, Full};
use serde::Deserialize;
use serde_yml::Value;
use sha2::{Digest, Sha256};
use std::{collections::HashMap, future::Future, pin::Pin, sync::Arc};
use tokio::sync::RwLock;
pub struct CacheKind;
#[derive(Deserialize)]
struct CacheConfig {
next: DynNode,
}
struct Cache {
entries: RwLock<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_yml::from_value::<CacheConfig>(config)?;
Ok(Arc::new(Cache {
config,
entries: HashMap::new().into(),
}))
}
}
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 {
// not very fast
let mut hasher = Sha256::new();
hasher.update(request.method().as_str().len().to_be_bytes());
hasher.update(request.method().as_str());
hasher.update(request.uri().path().len().to_be_bytes());
hasher.update(request.uri().path());
hasher.update(if request.uri().query().is_some() {
[1]
} else {
[0]
});
if let Some(q) = request.uri().query() {
hasher.update(q.len().to_be_bytes());
hasher.update(q);
}
hasher.update(request.headers().len().to_be_bytes());
for (k, v) in request.headers() {
hasher.update(k.as_str().len().to_be_bytes());
hasher.update(v.as_bytes().len().to_be_bytes());
hasher.update(k);
hasher.update(v);
}
let key: [u8; 32] = hasher.finalize().try_into().unwrap();
if let Some(resp) = self.entries.read().await.get(&key) {
return Ok(resp
.to_owned()
.map(|b| Full::new(b).map_err(|e| match e {}).boxed()));
}
let response = self.config.next.handle(context, request).await?;
let h = response.headers().to_owned();
let s = response.status().to_owned();
let body = response.collect().await?.to_bytes();
let mut r1 = Response::new(Full::new(body.clone()).map_err(|e| match e {}).boxed());
*r1.headers_mut() = h.clone();
*r1.status_mut() = s.clone();
let mut r2 = Response::new(body);
*r2.headers_mut() = h;
*r2.status_mut() = s;
self.entries.write().await.insert(key, r2);
Ok(r1)
})
}
}
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