From 1589268ebac343c9b7d7ea1032be812960d3ea39 Mon Sep 17 00:00:00 2001 From: Greg Heartsfield Date: Sun, 12 Dec 2021 10:20:23 -0600 Subject: [PATCH] fix: use database to publish all events This fixes a race condition where a publisher might send an event, and immediately after issue a subscription for the same event ID. Prior to this change, that event would have been published on the broadcast channel (and ignored by our publisher, because they had not yet issued the subscription), but not yet committed to the database. Their subscription would trigger a database query which would return zero results. Therefore, they would never see the event they published. The noscl tool is one client that would suffer from this. Now, all events are broadcast only after they exist in the database, so a late subscription will always return the event. --- src/db.rs | 3 +++ src/main.rs | 13 ++++--------- 2 files changed, 7 insertions(+), 9 deletions(-) diff --git a/src/db.rs b/src/db.rs index 62065a2..6fbaa32 100644 --- a/src/db.rs +++ b/src/db.rs @@ -67,6 +67,7 @@ CREATE INDEX IF NOT EXISTS pubkey_ref_index ON pubkey_ref(referenced_pubkey); /// Spawn a database writer that persists events to the SQLite store. pub async fn db_writer( mut event_rx: tokio::sync::mpsc::Receiver, + bcast_tx: tokio::sync::broadcast::Sender, ) -> tokio::task::JoinHandle> { task::spawn_blocking(move || { let mut conn = Connection::open_with_flags( @@ -94,6 +95,8 @@ pub async fn db_writer( info!("nothing inserted (dupe?)"); } else { info!("persisted event: {}", event.get_event_id_prefix()); + // send this out to all clients + bcast_tx.send(event.clone()).ok(); } } Err(err) => { diff --git a/src/main.rs b/src/main.rs index a8ff114..1563c70 100644 --- a/src/main.rs +++ b/src/main.rs @@ -44,8 +44,10 @@ fn main() -> Result<(), Error> { // validated events that need to be persisted are sent to the // database on via this channel. let (event_tx, event_rx) = mpsc::channel::(16); - // start the database writer thread. - db::db_writer(event_rx).await; + // start the database writer thread. Give it a channel for + // writing events, and for publishing events that have been + // written (to all connected clients). + db::db_writer(event_rx, bcast_tx.clone()).await; // establish a channel for letting all threads now about a // requested server shutdown. let (invoke_shutdown, _) = broadcast::channel::<()>(1); @@ -86,7 +88,6 @@ async fn nostr_server( mut shutdown: Receiver<()>, ) { // get a broadcast channel for clients to communicate on - // wrap the TCP stream in a websocket. let mut bcast_rx = broadcast.subscribe(); // upgrade the TCP connection to WebSocket let conn = tokio_tungstenite::accept_async(stream).await; @@ -154,18 +155,12 @@ async fn nostr_server( // Write this to the database event_tx.send(e.clone()).await.ok(); client_published_event_count += 1; - // send this event to everyone listening. - let bcast_res = broadcast.send(e); - if bcast_res.is_err() { - warn!("could not send broadcast message: {:?}", bcast_res); - } }, Err(_) => {info!("client {} sent an invalid event", cid)} } }, Some(Ok(SubMsg(s))) => { debug!("client {} requesting a subscription", cid); - // subscription handling consists of: // * registering the subscription so future events can be matched // * making a channel to cancel to request later