max_subscriptions, default is 32

sample/sample.config.ron

@@ -18,4 +18,5 @@ FriendlyConfig(
     // This is a bad idea in production, but useful for testing or for dumping
     // your entire relay
     allow_scraping: true,
+    max_subscriptions: 32,
 )

src/config.rs

@@ -19,6 +19,7 @@ pub struct FriendlyConfig {
     pub user_hex_keys: Vec<String>,
     pub verify_events: bool,
     pub allow_scraping: bool,
+    pub max_subscriptions: usize,
 }
 
 impl Default for FriendlyConfig {
@@ -38,6 +39,7 @@ impl Default for FriendlyConfig {
             user_hex_keys: vec![],
             verify_events: true,
             allow_scraping: false,
+            max_subscriptions: 32,
         }
     }
 }
@@ -59,6 +61,7 @@ impl FriendlyConfig {
             user_hex_keys,
             verify_events,
             allow_scraping,
+            max_subscriptions,
         } = self;
 
         let mut public_key: Option<Pubkey> = None;
@@ -89,6 +92,7 @@ impl FriendlyConfig {
             user_hex_keys,
             verify_events,
             allow_scraping,
+            max_subscriptions,
         })
     }
 }
@@ -110,4 +114,5 @@ pub struct Config {
     pub user_hex_keys: Vec<String>,
     pub verify_events: bool,
     pub allow_scraping: bool,
+    pub max_subscriptions: usize,
 }

src/main.rs

@@ -267,7 +267,7 @@ async fn handle_http_request(
                         }
                     }
 
-                    // DecrementIncrement count of active websockets
+                    // Decrement count of active websockets
                     let old_num_websockets = GLOBALS.num_clients.fetch_sub(1, Ordering::SeqCst);
 
                     log::info!(

src/nostr.rs

@@ -62,6 +62,19 @@ impl WebSocketService {
 
         log::info!("SUBID={}", subid);
 
+        let max_subscriptions = GLOBALS.config.read().await.max_subscriptions;
+        if self.subscriptions.len() >= max_subscriptions {
+            let reply = NostrReply::Closed(
+                &subid,
+                NostrReplyPrefix::RateLimited,
+                format!(
+                    "No more than {max_subscriptions} subscriptions are allowed at any one time"
+                ),
+            );
+            self.websocket.send(Message::text(reply.as_json())).await?;
+            return Ok(());
+        }
+
         // Read the filter into the session buffer
         let mut filters: Vec<OwnedFilter> = Vec::new();
         loop {