From 4943cf5b1107649c74ad7dce1ecd76eb2fb762cd Mon Sep 17 00:00:00 2001
From: Kurt Roeckx <kurt@roeckx.be>
Date: Sun, 15 Aug 2021 15:41:48 +0200
Subject: [PATCH] Get the auth chain non-recursive

---
 src/server_server.rs | 78 ++++++++++++++++++++------------------------
 1 file changed, 36 insertions(+), 42 deletions(-)

diff --git a/src/server_server.rs b/src/server_server.rs
index a4bfda5..c1ede52 100644
--- a/src/server_server.rs
+++ b/src/server_server.rs
@@ -1856,28 +1856,51 @@ fn get_auth_chain(
 ) -> Result<impl Iterator<Item = EventId> + '_> {
     let mut full_auth_chain = HashSet::new();
 
-    let starting_events = starting_events
+    let mut events = starting_events
         .iter()
         .map(|id| {
             db.rooms
                 .get_or_create_shorteventid(id, &db.globals)
-                .map(|s| (s, id))
+                .map(|s| (s, id.clone()))
         })
         .collect::<Result<Vec<_>>>()?;
 
     let mut cache = db.rooms.auth_chain_cache();
 
-    for (sevent_id, event_id) in starting_events {
-        if let Some(cached) = cache.get_mut(&sevent_id) {
-            full_auth_chain.extend(cached.iter().cloned());
-        } else {
-            drop(cache);
-            let mut auth_chain = HashSet::new();
-            get_auth_chain_recursive(&event_id, &mut auth_chain, db)?;
-            cache = db.rooms.auth_chain_cache();
-            cache.insert(sevent_id, auth_chain.clone());
-            full_auth_chain.extend(auth_chain);
-        };
+    while events.len() != 0 {
+        let mut new_events = Vec::new();
+        for (sevent_id, event_id) in &events {
+            if let Some(cached) = cache.get_mut(&sevent_id) {
+                full_auth_chain.extend(cached.iter().cloned());
+            } else {
+                drop(cache);
+                let mut auth_chain = HashSet::new();
+                let r = db.rooms.get_pdu(&event_id);
+                match r {
+                    Ok(Some(pdu)) => {
+                        for auth_event in &pdu.auth_events {
+                            let sauthevent = db
+                                .rooms
+                                .get_or_create_shorteventid(auth_event, &db.globals)?;
+                            if !auth_chain.contains(&sauthevent) {
+                                auth_chain.insert(sauthevent);
+                                new_events.push((sauthevent, auth_event.clone()));
+                            }
+                        }
+                    }
+                    Ok(None) => {
+                        warn!("Could not find pdu mentioned in auth events.");
+                    }
+                    Err(e) => {
+                        warn!("Could not load event in auth chain: {}", e);
+                    }
+                }
+                cache = db.rooms.auth_chain_cache();
+                cache.insert(*sevent_id, auth_chain.clone());
+                full_auth_chain.extend(auth_chain);
+            };
+        }
+        events = new_events;
     }
 
     drop(cache);
@@ -1887,35 +1910,6 @@ fn get_auth_chain(
         .filter_map(move |sid| db.rooms.get_eventid_from_short(sid).ok()))
 }
 
-fn get_auth_chain_recursive(
-    event_id: &EventId,
-    found: &mut HashSet<u64>,
-    db: &Database,
-) -> Result<()> {
-    let r = db.rooms.get_pdu(&event_id);
-    match r {
-        Ok(Some(pdu)) => {
-            for auth_event in &pdu.auth_events {
-                let sauthevent = db
-                    .rooms
-                    .get_or_create_shorteventid(auth_event, &db.globals)?;
-                if !found.contains(&sauthevent) {
-                    found.insert(sauthevent);
-                    get_auth_chain_recursive(&auth_event, found, db)?;
-                }
-            }
-        }
-        Ok(None) => {
-            warn!("Could not find pdu mentioned in auth events.");
-        }
-        Err(e) => {
-            warn!("Could not load event in auth chain: {}", e);
-        }
-    }
-
-    Ok(())
-}
-
 #[cfg_attr(
     feature = "conduit_bin",
     get("/_matrix/federation/v1/event/<_>", data = "<body>")