From 88e801ad97acec195c296a693af9031e54e9f95e Mon Sep 17 00:00:00 2001
From: Thomas Eizinger <thomas@eizinger.io>
Date: Sat, 20 Sep 2025 05:14:12 +0000
Subject: [PATCH] fix(gateway): re-join topic in phoenix-channel on error
 (#10397)

For whatever reason, we seem to sometimes lose the association with the
"room" we are meant to be in in order to send messages to the portal.
Without joining the right room, messages get dropped silently.

To fix this, we re-join the room on such errors. Long-term, this will be
fixed by ditching phoenix-channel in favor of simple HTTP requests.

Related: #9649
---
 rust/gateway/src/eventloop.rs | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/rust/gateway/src/eventloop.rs b/rust/gateway/src/eventloop.rs
index fb4e29848..86e5559ed 100644
--- a/rust/gateway/src/eventloop.rs
+++ b/rust/gateway/src/eventloop.rs
@@ -652,6 +652,16 @@ async fn phoenix_channel_event_loop(
                     break;
                 }
             }
+            Either::Left((
+                Ok(phoenix_channel::Event::ErrorResponse {
+                    topic,
+                    res: phoenix_channel::ErrorReply::UnmatchedTopic,
+                    ..
+                }),
+                _,
+            )) => {
+                portal.join(topic, ());
+            }
             Either::Left((Ok(phoenix_channel::Event::ErrorResponse { topic, req_id, res }), _)) => {
                 tracing::warn!(%topic, %req_id, "Request failed: {res:?}");
             }