Merge pull request #85 from pubky/feat/no-wasted-cache

feat(server): pkarr relay should return expired packets as a last resort

server/src/handlers.rs

@@ -4,6 +4,7 @@ use axum::{extract::State, response::IntoResponse};
 
 use bytes::Bytes;
 use http::{header, StatusCode};
+use pkarr::mainline::MutableItem;
 use tracing::error;
 
 use pkarr::{PublicKey, DEFAULT_MAXIMUM_TTL, DEFAULT_MINIMUM_TTL};
@@ -50,22 +51,37 @@ pub async fn get(
     let public_key = PublicKey::try_from(public_key.as_str())
         .map_err(|error| Error::new(StatusCode::BAD_REQUEST, Some(error)))?;
 
-    if let Some(signed_packet) =
-        state
-            .client
-            .resolve(&public_key)
-            .await
-            .map_err(|error| match error {
-                pkarr::Error::DhtIsShutdown => {
-                    error!("Dht is shutdown");
-                    Error::with_status(StatusCode::INTERNAL_SERVER_ERROR)
-                }
-                error => {
-                    error!(?error, "Unexpected error");
-                    Error::with_status(StatusCode::INTERNAL_SERVER_ERROR)
-                }
-            })?
-    {
+    let signed_packet = {
+        if let Some(signed_packet) =
+            state
+                .client
+                .resolve(&public_key)
+                .await
+                .map_err(|error| match error {
+                    pkarr::Error::DhtIsShutdown => {
+                        error!("Dht is shutdown");
+                        Error::with_status(StatusCode::INTERNAL_SERVER_ERROR)
+                    }
+                    error => {
+                        error!(?error, "Unexpected error");
+                        Error::with_status(StatusCode::INTERNAL_SERVER_ERROR)
+                    }
+                })?
+        {
+            Some(signed_packet)
+        } else {
+            // Respond with what we have, even if expired.
+            // TODO: move this fallback to the client itself, closing #67
+            state
+                .client
+                .cache()
+                .get_read_only(&MutableItem::target_from_key(public_key.as_bytes(), &None))
+        }
+    };
+
+    if let Some(signed_packet) = signed_packet {
+        tracing::debug!(?public_key, "cache hit responding with packet!");
+
         let body = signed_packet.to_relay_payload();
 
         let ttl = signed_packet.ttl(DEFAULT_MINIMUM_TTL, DEFAULT_MAXIMUM_TTL);