fix(host): Backoff after MAX_RETRIES (#429)

bin/host/src/fetcher/mod.rs

@@ -67,6 +67,8 @@ where
 
     /// Get the preimage for the given key.
     pub async fn get_preimage(&self, key: B256) -> Result<Vec<u8>> {
+        const MAX_RETRIES: usize = 32;
+
         trace!(target: "fetcher", "Pre-image requested. Key: {key}");
 
         // Acquire a read lock on the key-value store.
@@ -77,12 +79,20 @@ where
         drop(kv_lock);
 
         // Use a loop to keep retrying the prefetch as long as the key is not found
+        let mut retries = 0;
         while preimage.is_none() && self.last_hint.is_some() {
+            if retries >= MAX_RETRIES {
+                tracing::error!(target: "fetcher", "Max retries exceeded.");
+                anyhow::bail!("Max retries exceeded.");
+            }
+
             let hint = self.last_hint.as_ref().expect("Cannot be None");
             self.prefetch(hint).await?;
 
             let kv_lock = self.kv_store.read().await;
             preimage = kv_lock.get(key);
+
+            retries += 1;
         }
 
         preimage.ok_or_else(|| anyhow!("Preimage not found."))

bin/host/src/server.rs

@@ -63,7 +63,10 @@ where
         // Spawn tasks for the futures and wait for them to complete.
         let server = tokio::task::spawn(server_fut);
         let hint_router = tokio::task::spawn(hinter_fut);
-        tokio::try_join!(server, hint_router).map_err(|e| anyhow!(e))?;
+        tokio::select! {
+            s = server => s.map_err(|e| anyhow!(e))?,
+            h = hint_router => h.map_err(|e| anyhow!(e))?,
+        }
 
         Ok(())
     }