fix: don't allow more than 50 PDUs in a transaction

src/database/sending.rs

@@ -54,14 +54,15 @@ impl Sending {
                     ))
                 })
                 .filter_map(|r| r.ok())
+                .filter(|pdu| !pdu.is_empty()) // Skip reservation key
+                .take(50)
+            // This should not contain more than 50 anyway
             {
-                if !pdu.is_empty() {
                 current_transactions
                     .entry(server)
                     .or_insert_with(Vec::new)
                     .push(pdu);
             }
-            }
 
             for (server, pdus) in current_transactions {
                 futures.push(Self::handle_event(server, pdus, &globals, &rooms));
@@ -95,7 +96,9 @@ impl Sending {
                                     .filter_map(|r| r.ok())
                                     .map(|k| {
                                         k.subslice(prefix.len(), k.len() - prefix.len())
-                                    }).collect::<Vec<_>>();
+                                    })
+                                    .take(50)
+                                    .collect::<Vec<_>>();
 
                                 if !new_pdus.is_empty() {
                                     for pdu_id in &new_pdus {
@@ -108,6 +111,7 @@ impl Sending {
                                     futures.push(Self::handle_event(server, new_pdus, &globals, &rooms));
                                 } else {
                                     servercurrentpdus.remove(&prefix).unwrap();
+                                    // servercurrentpdus with the prefix should be empty now
                                 }
                             }
                             Err((_server, _e)) => {