feat: ask for backfill

src/api/client_server/context.rs

@@ -27,25 +27,24 @@ pub async fn get_context_route(
 
     let mut lazy_loaded = HashSet::new();
 
-    let base_pdu_id = services()
+    let base_token = services()
         .rooms
         .timeline
-        .get_pdu_id(&body.event_id)?
+        .get_pdu_count(&body.event_id)?
         .ok_or(Error::BadRequest(
             ErrorKind::NotFound,
             "Base event id not found.",
         ))?;
 
-    let base_token = services().rooms.timeline.pdu_count(&base_pdu_id)?;
+    let base_event =
-
+        services()
-    let base_event = services()
+            .rooms
-        .rooms
+            .timeline
-        .timeline
+            .get_pdu(&body.event_id)?
-        .get_pdu_from_id(&base_pdu_id)?
+            .ok_or(Error::BadRequest(
-        .ok_or(Error::BadRequest(
+                ErrorKind::NotFound,
-            ErrorKind::NotFound,
+                "Base event not found.",
-            "Base event not found.",
+            ))?;
-        ))?;
 
     let room_id = base_event.room_id.clone();
 
@@ -97,10 +96,7 @@ pub async fn get_context_route(
         }
     }
 
-    let start_token = events_before
+    let start_token = events_before.last().map(|(count, _)| count.stringify());
-        .last()
-        .and_then(|(pdu_id, _)| services().rooms.timeline.pdu_count(pdu_id).ok())
-        .map(|count| count.to_string());
 
     let events_before: Vec<_> = events_before
         .into_iter()
@@ -151,10 +147,7 @@ pub async fn get_context_route(
         .state_full_ids(shortstatehash)
         .await?;
 
-    let end_token = events_after
+    let end_token = events_after.last().map(|(count, _)| count.stringify());
-        .last()
-        .and_then(|(pdu_id, _)| services().rooms.timeline.pdu_count(pdu_id).ok())
-        .map(|count| count.to_string());
 
     let events_after: Vec<_> = events_after
         .into_iter()

src/api/client_server/membership.rs

@@ -714,8 +714,10 @@ async fn join_room_by_id_helper(
                     .ok()?
             },
         )
-        .map_err(|_e| Error::BadRequest(ErrorKind::InvalidParam, "Auth check failed"))?
+        .map_err(|e| {
-        {
+            warn!("Auth check failed: {e}");
+            Error::BadRequest(ErrorKind::InvalidParam, "Auth check failed")
+        })? {
             return Err(Error::BadRequest(
                 ErrorKind::InvalidParam,
                 "Auth check failed",

src/api/client_server/message.rs

@@ -1,4 +1,7 @@
-use crate::{service::pdu::PduBuilder, services, utils, Error, Result, Ruma};
+use crate::{
+    service::{pdu::PduBuilder, rooms::timeline::PduCount},
+    services, utils, Error, Result, Ruma,
+};
 use ruma::{
     api::client::{
         error::ErrorKind,
@@ -122,17 +125,17 @@ pub async fn get_message_events_route(
     }
 
     let from = match body.from.clone() {
-        Some(from) => from
+        Some(from) => PduCount::try_from_string(&from)?,
-            .parse()
-            .map_err(|_| Error::BadRequest(ErrorKind::InvalidParam, "Invalid `from` value."))?,
-
         None => match body.dir {
-            ruma::api::client::Direction::Forward => 0,
+            ruma::api::client::Direction::Forward => PduCount::min(),
-            ruma::api::client::Direction::Backward => u64::MAX,
+            ruma::api::client::Direction::Backward => PduCount::max(),
         },
     };
 
-    let to = body.to.as_ref().map(|t| t.parse());
+    let to = body
+        .to
+        .as_ref()
+        .and_then(|t| PduCount::try_from_string(&t).ok());
 
     services().rooms.lazy_loading.lazy_load_confirm_delivery(
         sender_user,
@@ -158,15 +161,7 @@ pub async fn get_message_events_route(
                 .pdus_after(sender_user, &body.room_id, from)?
                 .take(limit)
                 .filter_map(|r| r.ok()) // Filter out buggy events
-                .filter_map(|(pdu_id, pdu)| {
+                .take_while(|&(k, _)| Some(k) != to) // Stop at `to`
-                    services()
-                        .rooms
-                        .timeline
-                        .pdu_count(&pdu_id)
-                        .map(|pdu_count| (pdu_count, pdu))
-                        .ok()
-                })
-                .take_while(|&(k, _)| Some(Ok(k)) != to) // Stop at `to`
                 .collect();
 
             for (_, event) in &events_after {
@@ -192,26 +187,23 @@ pub async fn get_message_events_route(
                 .map(|(_, pdu)| pdu.to_room_event())
                 .collect();
 
-            resp.start = from.to_string();
+            resp.start = from.stringify();
-            resp.end = next_token.map(|count| count.to_string());
+            resp.end = next_token.map(|count| count.stringify());
             resp.chunk = events_after;
         }
         ruma::api::client::Direction::Backward => {
+            services()
+                .rooms
+                .timeline
+                .backfill_if_required(&body.room_id, from)
+                .await?;
             let events_before: Vec<_> = services()
                 .rooms
                 .timeline
                 .pdus_until(sender_user, &body.room_id, from)?
                 .take(limit)
                 .filter_map(|r| r.ok()) // Filter out buggy events
-                .filter_map(|(pdu_id, pdu)| {
+                .take_while(|&(k, _)| Some(k) != to) // Stop at `to`
-                    services()
-                        .rooms
-                        .timeline
-                        .pdu_count(&pdu_id)
-                        .map(|pdu_count| (pdu_count, pdu))
-                        .ok()
-                })
-                .take_while(|&(k, _)| Some(Ok(k)) != to) // Stop at `to`
                 .collect();
 
             for (_, event) in &events_before {
@@ -237,8 +229,8 @@ pub async fn get_message_events_route(
                 .map(|(_, pdu)| pdu.to_room_event())
                 .collect();
 
-            resp.start = from.to_string();
+            resp.start = from.stringify();
-            resp.end = next_token.map(|count| count.to_string());
+            resp.end = next_token.map(|count| count.stringify());
             resp.chunk = events_before;
         }
     }

src/api/client_server/read_marker.rs

@@ -1,4 +1,4 @@
-use crate::{services, Error, Result, Ruma};
+use crate::{service::rooms::timeline::PduCount, services, Error, Result, Ruma};
 use ruma::{
     api::client::{error::ErrorKind, read_marker::set_read_marker, receipt::create_receipt},
     events::{
@@ -42,18 +42,28 @@ pub async fn set_read_marker_route(
     }
 
     if let Some(event) = &body.private_read_receipt {
-        services().rooms.edus.read_receipt.private_read_set(
+        let count = services()
-            &body.room_id,
+            .rooms
-            sender_user,
+            .timeline
-            services()
+            .get_pdu_count(event)?
-                .rooms
+            .ok_or(Error::BadRequest(
-                .timeline
+                ErrorKind::InvalidParam,
-                .get_pdu_count(event)?
+                "Event does not exist.",
-                .ok_or(Error::BadRequest(
+            ))?;
+        let count = match count {
+            PduCount::Backfilled(_) => {
+                return Err(Error::BadRequest(
                     ErrorKind::InvalidParam,
-                    "Event does not exist.",
+                    "Read receipt is in backfilled timeline",
-                ))?,
+                ))
-        )?;
+            }
+            PduCount::Normal(c) => c,
+        };
+        services()
+            .rooms
+            .edus
+            .read_receipt
+            .private_read_set(&body.room_id, sender_user, count)?;
     }
 
     if let Some(event) = &body.read_receipt {
@@ -142,17 +152,27 @@ pub async fn create_receipt_route(
             )?;
         }
         create_receipt::v3::ReceiptType::ReadPrivate => {
+            let count = services()
+                .rooms
+                .timeline
+                .get_pdu_count(&body.event_id)?
+                .ok_or(Error::BadRequest(
+                    ErrorKind::InvalidParam,
+                    "Event does not exist.",
+                ))?;
+            let count = match count {
+                PduCount::Backfilled(_) => {
+                    return Err(Error::BadRequest(
+                        ErrorKind::InvalidParam,
+                        "Read receipt is in backfilled timeline",
+                    ))
+                }
+                PduCount::Normal(c) => c,
+            };
             services().rooms.edus.read_receipt.private_read_set(
                 &body.room_id,
                 sender_user,
-                services()
+                count,
-                    .rooms
-                    .timeline
-                    .get_pdu_count(&body.event_id)?
-                    .ok_or(Error::BadRequest(
-                        ErrorKind::InvalidParam,
-                        "Event does not exist.",
-                    ))?,
             )?;
         }
         _ => return Err(Error::bad_database("Unsupported receipt type")),

src/api/client_server/sync.rs

@@ -1,4 +1,4 @@
-use crate::{services, Error, Result, Ruma, RumaResponse};
+use crate::{service::rooms::timeline::PduCount, services, Error, Result, Ruma, RumaResponse};
 use ruma::{
     api::client::{
         filter::{FilterDefinition, LazyLoadOptions},
@@ -172,6 +172,7 @@ async fn sync_helper(
     let watcher = services().globals.watch(&sender_user, &sender_device);
 
     let next_batch = services().globals.current_count()?;
+    let next_batchcount = PduCount::Normal(next_batch);
     let next_batch_string = next_batch.to_string();
 
     // Load filter
@@ -197,6 +198,7 @@ async fn sync_helper(
         .clone()
         .and_then(|string| string.parse().ok())
         .unwrap_or(0);
+    let sincecount = PduCount::Normal(since);
 
     let mut presence_updates = HashMap::new();
     let mut left_encrypted_users = HashSet::new(); // Users that have left any encrypted rooms the sender was in
@@ -241,12 +243,12 @@ async fn sync_helper(
             .rooms
             .timeline
             .last_timeline_count(&sender_user, &room_id)?
-            > since
+            > sincecount
         {
             let mut non_timeline_pdus = services()
                 .rooms
                 .timeline
-                .pdus_until(&sender_user, &room_id, u64::MAX)?
+                .pdus_until(&sender_user, &room_id, PduCount::max())?
                 .filter_map(|r| {
                     // Filter out buggy events
                     if r.is_err() {
@@ -254,13 +256,7 @@ async fn sync_helper(
                     }
                     r.ok()
                 })
-                .take_while(|(pduid, _)| {
+                .take_while(|(pducount, _)| pducount > &sincecount);
-                    services()
-                        .rooms
-                        .timeline
-                        .pdu_count(pduid)
-                        .map_or(false, |count| count > since)
-                });
 
             // Take the last 10 events for the timeline
             timeline_pdus = non_timeline_pdus
@@ -295,7 +291,7 @@ async fn sync_helper(
             &sender_user,
             &sender_device,
             &room_id,
-            since,
+            sincecount,
         )?;
 
         // Database queries:
@@ -492,7 +488,7 @@ async fn sync_helper(
                 &sender_device,
                 &room_id,
                 lazy_loaded,
-                next_batch,
+                next_batchcount,
             );
 
             (
@@ -582,7 +578,7 @@ async fn sync_helper(
                 &sender_device,
                 &room_id,
                 lazy_loaded,
-                next_batch,
+                next_batchcount,
             );
 
             let encrypted_room = services()
@@ -711,10 +707,14 @@ async fn sync_helper(
 
         let prev_batch = timeline_pdus
             .first()
-            .map_or(Ok::<_, Error>(None), |(pdu_id, _)| {
+            .map_or(Ok::<_, Error>(None), |(pdu_count, _)| {
-                Ok(Some(
+                Ok(Some(match pdu_count {
-                    services().rooms.timeline.pdu_count(pdu_id)?.to_string(),
+                    PduCount::Backfilled(_) => {
-                ))
+                        error!("timeline in backfill state?!");
+                        "0".to_owned()
+                    }
+                    PduCount::Normal(c) => c.to_string(),
+                }))
             })?;
 
         let room_events: Vec<_> = timeline_pdus

src/api/server_server.rs

@@ -629,6 +629,37 @@ pub async fn get_public_rooms_route(
     })
 }
 
+pub fn parse_incoming_pdu(
+    pdu: &RawJsonValue,
+) -> Result<(OwnedEventId, CanonicalJsonObject, OwnedRoomId)> {
+    let value: CanonicalJsonObject = serde_json::from_str(pdu.get()).map_err(|e| {
+        warn!("Error parsing incoming event {:?}: {:?}", pdu, e);
+        Error::BadServerResponse("Invalid PDU in server response")
+    })?;
+
+    let room_id: OwnedRoomId = value
+        .get("room_id")
+        .and_then(|id| RoomId::parse(id.as_str()?).ok())
+        .ok_or(Error::BadRequest(
+            ErrorKind::InvalidParam,
+            "Invalid room id in pdu",
+        ))?;
+
+    let room_version_id = services().rooms.state.get_room_version(&room_id)?;
+
+    let (event_id, value) = match gen_event_id_canonical_json(&pdu, &room_version_id) {
+        Ok(t) => t,
+        Err(_) => {
+            // Event could not be converted to canonical json
+            return Err(Error::BadRequest(
+                ErrorKind::InvalidParam,
+                "Could not convert event to canonical json.",
+            ));
+        }
+    };
+    Ok((event_id, value, room_id))
+}
+
 /// # `PUT /_matrix/federation/v1/send/{txnId}`
 ///
 /// Push EDUs and PDUs to this server.
@@ -657,36 +688,7 @@ pub async fn send_transaction_message_route(
     // let mut auth_cache = EventMap::new();
 
     for pdu in &body.pdus {
-        let value: CanonicalJsonObject = serde_json::from_str(pdu.get()).map_err(|e| {
+        let (event_id, value, room_id) = parse_incoming_pdu(&pdu)?;
-            warn!("Error parsing incoming event {:?}: {:?}", pdu, e);
-            Error::BadServerResponse("Invalid PDU in server response")
-        })?;
-
-        let room_id: OwnedRoomId = match value
-            .get("room_id")
-            .and_then(|id| RoomId::parse(id.as_str()?).ok())
-        {
-            Some(id) => id,
-            None => {
-                // Event is invalid
-                continue;
-            }
-        };
-
-        let room_version_id = match services().rooms.state.get_room_version(&room_id) {
-            Ok(v) => v,
-            Err(_) => {
-                continue;
-            }
-        };
-
-        let (event_id, value) = match gen_event_id_canonical_json(pdu, &room_version_id) {
-            Ok(t) => t,
-            Err(_) => {
-                // Event could not be converted to canonical json
-                continue;
-            }
-        };
         // We do not add the event_id field to the pdu here because of signature and hashes checks
 
         services()
@@ -1017,7 +1019,7 @@ pub async fn get_backfill_route(
                 Ok(true),
             )
         })
-        .map(|(pdu_id, _)| services().rooms.timeline.get_pdu_json_from_id(&pdu_id))
+        .map(|(_, pdu)| services().rooms.timeline.get_pdu_json(&pdu.event_id))
         .filter_map(|r| r.ok().flatten())
         .map(|pdu| PduEvent::convert_to_outgoing_federation_event(pdu))
         .collect();

src/database/key_value/rooms/timeline.rs

@@ -7,6 +7,8 @@ use tracing::error;
 
 use crate::{database::KeyValueDatabase, service, services, utils, Error, PduEvent, Result};
 
+use service::rooms::timeline::PduCount;
+
 impl service::rooms::timeline::Data for KeyValueDatabase {
     fn first_pdu_in_room(&self, room_id: &RoomId) -> Result<Option<Arc<PduEvent>>> {
         let prefix = services()
@@ -30,7 +32,7 @@ impl service::rooms::timeline::Data for KeyValueDatabase {
             .transpose()
     }
 
-    fn last_timeline_count(&self, sender_user: &UserId, room_id: &RoomId) -> Result<u64> {
+    fn last_timeline_count(&self, sender_user: &UserId, room_id: &RoomId) -> Result<PduCount> {
         match self
             .lasttimelinecount_cache
             .lock()
@@ -39,20 +41,18 @@ impl service::rooms::timeline::Data for KeyValueDatabase {
         {
             hash_map::Entry::Vacant(v) => {
                 if let Some(last_count) = self
-                    .pdus_until(sender_user, room_id, u64::MAX)?
+                    .pdus_until(sender_user, room_id, PduCount::max())?
-                    .filter_map(|r| {
+                    .find_map(|r| {
                         // Filter out buggy events
                         if r.is_err() {
                             error!("Bad pdu in pdus_since: {:?}", r);
                         }
                         r.ok()
                     })
-                    .map(|(pduid, _)| self.pdu_count(&pduid))
-                    .next()
                 {
-                    Ok(*v.insert(last_count?))
+                    Ok(*v.insert(last_count.0))
                 } else {
-                    Ok(0)
+                    Ok(PduCount::Normal(0))
                 }
             }
             hash_map::Entry::Occupied(o) => Ok(*o.get()),
@@ -60,11 +60,23 @@ impl service::rooms::timeline::Data for KeyValueDatabase {
     }
 
     /// Returns the `count` of this pdu's id.
-    fn get_pdu_count(&self, event_id: &EventId) -> Result<Option<u64>> {
+    fn get_pdu_count(&self, event_id: &EventId) -> Result<Option<PduCount>> {
-        self.eventid_pduid
+        Ok(self
+            .eventid_pduid
             .get(event_id.as_bytes())?
-            .map(|pdu_id| self.pdu_count(&pdu_id))
+            .map(|pdu_id| Ok::<_, Error>(PduCount::Normal(pdu_count(&pdu_id)?)))
-            .transpose()
+            .transpose()?
+            .map_or_else(
+                || {
+                    Ok::<_, Error>(
+                        self.eventid_backfillpduid
+                            .get(event_id.as_bytes())?
+                            .map(|pdu_id| Ok::<_, Error>(PduCount::Backfilled(pdu_count(&pdu_id)?)))
+                            .transpose()?,
+                    )
+                },
+                |x| Ok(Some(x)),
+            )?)
     }
 
     /// Returns the json of a pdu.
@@ -182,12 +194,6 @@ impl service::rooms::timeline::Data for KeyValueDatabase {
         })
     }
 
-    /// Returns the `count` of this pdu's id.
-    fn pdu_count(&self, pdu_id: &[u8]) -> Result<u64> {
-        utils::u64_from_bytes(&pdu_id[pdu_id.len() - size_of::<u64>()..])
-            .map_err(|_| Error::bad_database("PDU has invalid count bytes."))
-    }
-
     fn append_pdu(
         &self,
         pdu_id: &[u8],
@@ -203,7 +209,7 @@ impl service::rooms::timeline::Data for KeyValueDatabase {
         self.lasttimelinecount_cache
             .lock()
             .unwrap()
-            .insert(pdu.room_id.clone(), count);
+            .insert(pdu.room_id.clone(), PduCount::Normal(count));
 
         self.eventid_pduid.insert(pdu.event_id.as_bytes(), pdu_id)?;
         self.eventid_outlierpdu.remove(pdu.event_id.as_bytes())?;
@@ -211,6 +217,24 @@ impl service::rooms::timeline::Data for KeyValueDatabase {
         Ok(())
     }
 
+    fn prepend_backfill_pdu(
+        &self,
+        pdu_id: &[u8],
+        event_id: &EventId,
+        json: &CanonicalJsonObject,
+    ) -> Result<()> {
+        self.pduid_backfillpdu.insert(
+            pdu_id,
+            &serde_json::to_vec(json).expect("CanonicalJsonObject is always a valid"),
+        )?;
+
+        self.eventid_backfillpduid
+            .insert(event_id.as_bytes(), pdu_id)?;
+        self.eventid_outlierpdu.remove(event_id.as_bytes())?;
+
+        Ok(())
+    }
+
     /// Removes a pdu and creates a new one with the same id.
     fn replace_pdu(&self, pdu_id: &[u8], pdu: &PduEvent) -> Result<()> {
         if self.pduid_pdu.get(pdu_id)?.is_some() {
@@ -227,51 +251,14 @@ impl service::rooms::timeline::Data for KeyValueDatabase {
         }
     }
 
-    /// Returns an iterator over all events in a room that happened after the event with id `since`
-    /// in chronological order.
-    fn pdus_since<'a>(
-        &'a self,
-        user_id: &UserId,
-        room_id: &RoomId,
-        since: u64,
-    ) -> Result<Box<dyn Iterator<Item = Result<(Vec<u8>, PduEvent)>> + 'a>> {
-        let prefix = services()
-            .rooms
-            .short
-            .get_shortroomid(room_id)?
-            .expect("room exists")
-            .to_be_bytes()
-            .to_vec();
-
-        // Skip the first pdu if it's exactly at since, because we sent that last time
-        let mut first_pdu_id = prefix.clone();
-        first_pdu_id.extend_from_slice(&(since + 1).to_be_bytes());
-
-        let user_id = user_id.to_owned();
-
-        Ok(Box::new(
-            self.pduid_pdu
-                .iter_from(&first_pdu_id, false)
-                .take_while(move |(k, _)| k.starts_with(&prefix))
-                .map(move |(pdu_id, v)| {
-                    let mut pdu = serde_json::from_slice::<PduEvent>(&v)
-                        .map_err(|_| Error::bad_database("PDU in db is invalid."))?;
-                    if pdu.sender != user_id {
-                        pdu.remove_transaction_id()?;
-                    }
-                    Ok((pdu_id, pdu))
-                }),
-        ))
-    }
-
     /// Returns an iterator over all events and their tokens in a room that happened before the
     /// event with id `until` in reverse-chronological order.
     fn pdus_until<'a>(
         &'a self,
         user_id: &UserId,
         room_id: &RoomId,
-        until: u64,
+        until: PduCount,
-    ) -> Result<Box<dyn Iterator<Item = Result<(Vec<u8>, PduEvent)>> + 'a>> {
+    ) -> Result<Box<dyn Iterator<Item = Result<(PduCount, PduEvent)>> + 'a>> {
         // Create the first part of the full pdu id
         let prefix = services()
             .rooms
@@ -281,34 +268,63 @@ impl service::rooms::timeline::Data for KeyValueDatabase {
             .to_be_bytes()
             .to_vec();
 
-        let mut current = prefix.clone();
+        let mut current_backfill = prefix.clone();
-        current.extend_from_slice(&(until.saturating_sub(1)).to_be_bytes()); // -1 because we don't want event at `until`
+        // +1 so we don't send the base event
-
+        let backfill_count = match until {
-        let current: &[u8] = &current;
+            PduCount::Backfilled(x) => x + 1,
+            PduCount::Normal(_) => 0,
+        };
+        current_backfill.extend_from_slice(&backfill_count.to_be_bytes());
 
         let user_id = user_id.to_owned();
+        let user_id2 = user_id.to_owned();
+        let prefix2 = prefix.clone();
+
+        let backfill_iter = self
+            .pduid_backfillpdu
+            .iter_from(&current_backfill, false)
+            .take_while(move |(k, _)| k.starts_with(&prefix))
+            .map(move |(pdu_id, v)| {
+                let mut pdu = serde_json::from_slice::<PduEvent>(&v)
+                    .map_err(|_| Error::bad_database("PDU in db is invalid."))?;
+                if pdu.sender != user_id {
+                    pdu.remove_transaction_id()?;
+                }
+                let count = PduCount::Backfilled(pdu_count(&pdu_id)?);
+                Ok((count, pdu))
+            });
+
+        match until {
+            PduCount::Backfilled(_) => Ok(Box::new(backfill_iter)),
+            PduCount::Normal(x) => {
+                let mut current_normal = prefix2.clone();
+                // -1 so we don't send the base event
+                current_normal.extend_from_slice(&x.saturating_sub(1).to_be_bytes());
+                let normal_iter = self
+                    .pduid_pdu
+                    .iter_from(&current_normal, true)
+                    .take_while(move |(k, _)| k.starts_with(&prefix2))
+                    .map(move |(pdu_id, v)| {
+                        let mut pdu = serde_json::from_slice::<PduEvent>(&v)
+                            .map_err(|_| Error::bad_database("PDU in db is invalid."))?;
+                        if pdu.sender != user_id2 {
+                            pdu.remove_transaction_id()?;
+                        }
+                        let count = PduCount::Normal(pdu_count(&pdu_id)?);
+                        Ok((count, pdu))
+                    });
 
-        Ok(Box::new(
+                Ok(Box::new(normal_iter.chain(backfill_iter)))
-            self.pduid_pdu
+            }
-                .iter_from(current, true)
+        }
-                .take_while(move |(k, _)| k.starts_with(&prefix))
-                .map(move |(pdu_id, v)| {
-                    let mut pdu = serde_json::from_slice::<PduEvent>(&v)
-                        .map_err(|_| Error::bad_database("PDU in db is invalid."))?;
-                    if pdu.sender != user_id {
-                        pdu.remove_transaction_id()?;
-                    }
-                    Ok((pdu_id, pdu))
-                }),
-        ))
     }
 
     fn pdus_after<'a>(
         &'a self,
         user_id: &UserId,
         room_id: &RoomId,
-        from: u64,
+        from: PduCount,
-    ) -> Result<Box<dyn Iterator<Item = Result<(Vec<u8>, PduEvent)>> + 'a>> {
+    ) -> Result<Box<dyn Iterator<Item = Result<(PduCount, PduEvent)>> + 'a>> {
         // Create the first part of the full pdu id
         let prefix = services()
             .rooms
@@ -318,26 +334,55 @@ impl service::rooms::timeline::Data for KeyValueDatabase {
             .to_be_bytes()
             .to_vec();
 
-        let mut current = prefix.clone();
+        let mut current_normal = prefix.clone();
-        current.extend_from_slice(&(from + 1).to_be_bytes()); // +1 so we don't send the base event
+        // +1 so we don't send the base event
-
+        let normal_count = match from {
-        let current: &[u8] = &current;
+            PduCount::Normal(x) => x + 1,
+            PduCount::Backfilled(_) => 0,
+        };
+        current_normal.extend_from_slice(&normal_count.to_be_bytes());
 
         let user_id = user_id.to_owned();
+        let user_id2 = user_id.to_owned();
+        let prefix2 = prefix.clone();
+
+        let normal_iter = self
+            .pduid_pdu
+            .iter_from(&current_normal, false)
+            .take_while(move |(k, _)| k.starts_with(&prefix))
+            .map(move |(pdu_id, v)| {
+                let mut pdu = serde_json::from_slice::<PduEvent>(&v)
+                    .map_err(|_| Error::bad_database("PDU in db is invalid."))?;
+                if pdu.sender != user_id {
+                    pdu.remove_transaction_id()?;
+                }
+                let count = PduCount::Normal(pdu_count(&pdu_id)?);
+                Ok((count, pdu))
+            });
+
+        match from {
+            PduCount::Normal(_) => Ok(Box::new(normal_iter)),
+            PduCount::Backfilled(x) => {
+                let mut current_backfill = prefix2.clone();
+                // -1 so we don't send the base event
+                current_backfill.extend_from_slice(&x.saturating_sub(1).to_be_bytes());
+                let backfill_iter = self
+                    .pduid_backfillpdu
+                    .iter_from(&current_backfill, true)
+                    .take_while(move |(k, _)| k.starts_with(&prefix2))
+                    .map(move |(pdu_id, v)| {
+                        let mut pdu = serde_json::from_slice::<PduEvent>(&v)
+                            .map_err(|_| Error::bad_database("PDU in db is invalid."))?;
+                        if pdu.sender != user_id2 {
+                            pdu.remove_transaction_id()?;
+                        }
+                        let count = PduCount::Backfilled(pdu_count(&pdu_id)?);
+                        Ok((count, pdu))
+                    });
 
-        Ok(Box::new(
+                Ok(Box::new(backfill_iter.chain(normal_iter)))
-            self.pduid_pdu
+            }
-                .iter_from(current, false)
+        }
-                .take_while(move |(k, _)| k.starts_with(&prefix))
-                .map(move |(pdu_id, v)| {
-                    let mut pdu = serde_json::from_slice::<PduEvent>(&v)
-                        .map_err(|_| Error::bad_database("PDU in db is invalid."))?;
-                    if pdu.sender != user_id {
-                        pdu.remove_transaction_id()?;
-                    }
-                    Ok((pdu_id, pdu))
-                }),
-        ))
     }
 
     fn increment_notification_counts(
@@ -368,3 +413,9 @@ impl service::rooms::timeline::Data for KeyValueDatabase {
         Ok(())
     }
 }
+
+/// Returns the `count` of this pdu's id.
+fn pdu_count(pdu_id: &[u8]) -> Result<u64> {
+    utils::u64_from_bytes(&pdu_id[pdu_id.len() - size_of::<u64>()..])
+        .map_err(|_| Error::bad_database("PDU has invalid count bytes."))
+}

src/database/mod.rs

@@ -1,7 +1,10 @@
 pub mod abstraction;
 pub mod key_value;
 
-use crate::{services, utils, Config, Error, PduEvent, Result, Services, SERVICES};
+use crate::{
+    service::rooms::timeline::PduCount, services, utils, Config, Error, PduEvent, Result, Services,
+    SERVICES,
+};
 use abstraction::{KeyValueDatabaseEngine, KvTree};
 use directories::ProjectDirs;
 use lru_cache::LruCache;
@@ -71,7 +74,9 @@ pub struct KeyValueDatabase {
 
     //pub rooms: rooms::Rooms,
     pub(super) pduid_pdu: Arc<dyn KvTree>, // PduId = ShortRoomId + Count
+    pub(super) pduid_backfillpdu: Arc<dyn KvTree>, // PduId = ShortRoomId + Count
     pub(super) eventid_pduid: Arc<dyn KvTree>,
+    pub(super) eventid_backfillpduid: Arc<dyn KvTree>,
     pub(super) roomid_pduleaves: Arc<dyn KvTree>,
     pub(super) alias_roomid: Arc<dyn KvTree>,
     pub(super) aliasid_alias: Arc<dyn KvTree>, // AliasId = RoomId + Count
@@ -161,7 +166,7 @@ pub struct KeyValueDatabase {
     pub(super) shortstatekey_cache: Mutex<LruCache<u64, (StateEventType, String)>>,
     pub(super) our_real_users_cache: RwLock<HashMap<OwnedRoomId, Arc<HashSet<OwnedUserId>>>>,
     pub(super) appservice_in_room_cache: RwLock<HashMap<OwnedRoomId, HashMap<String, bool>>>,
-    pub(super) lasttimelinecount_cache: Mutex<HashMap<OwnedRoomId, u64>>,
+    pub(super) lasttimelinecount_cache: Mutex<HashMap<OwnedRoomId, PduCount>>,
 }
 
 impl KeyValueDatabase {
@@ -292,7 +297,9 @@ impl KeyValueDatabase {
             presenceid_presence: builder.open_tree("presenceid_presence")?,
             userid_lastpresenceupdate: builder.open_tree("userid_lastpresenceupdate")?,
             pduid_pdu: builder.open_tree("pduid_pdu")?,
+            pduid_backfillpdu: builder.open_tree("pduid_backfillpdu")?,
             eventid_pduid: builder.open_tree("eventid_pduid")?,
+            eventid_backfillpduid: builder.open_tree("eventid_backfillpduid")?,
             roomid_pduleaves: builder.open_tree("roomid_pduleaves")?,
 
             alias_roomid: builder.open_tree("alias_roomid")?,

src/service/rooms/lazy_loading/mod.rs

@@ -9,11 +9,13 @@ use ruma::{DeviceId, OwnedDeviceId, OwnedRoomId, OwnedUserId, RoomId, UserId};
 
 use crate::Result;
 
+use super::timeline::PduCount;
+
 pub struct Service {
     pub db: &'static dyn Data,
 
     pub lazy_load_waiting:
-        Mutex<HashMap<(OwnedUserId, OwnedDeviceId, OwnedRoomId, u64), HashSet<OwnedUserId>>>,
+        Mutex<HashMap<(OwnedUserId, OwnedDeviceId, OwnedRoomId, PduCount), HashSet<OwnedUserId>>>,
 }
 
 impl Service {
@@ -36,7 +38,7 @@ impl Service {
         device_id: &DeviceId,
         room_id: &RoomId,
         lazy_load: HashSet<OwnedUserId>,
-        count: u64,
+        count: PduCount,
     ) {
         self.lazy_load_waiting.lock().unwrap().insert(
             (
@@ -55,7 +57,7 @@ impl Service {
         user_id: &UserId,
         device_id: &DeviceId,
         room_id: &RoomId,
-        since: u64,
+        since: PduCount,
     ) -> Result<()> {
         if let Some(user_ids) = self.lazy_load_waiting.lock().unwrap().remove(&(
             user_id.to_owned(),

src/service/rooms/state_accessor/mod.rs

@@ -14,7 +14,7 @@ use ruma::{
         },
         StateEventType,
     },
-    EventId, OwnedServerName, OwnedUserId, RoomId, ServerName, UserId,
+    EventId, OwnedServerName, RoomId, ServerName, UserId,
 };
 use tracing::error;
 

src/service/rooms/timeline/data.rs

@@ -4,12 +4,14 @@ use ruma::{CanonicalJsonObject, EventId, OwnedUserId, RoomId, UserId};
 
 use crate::{PduEvent, Result};
 
+use super::PduCount;
+
 pub trait Data: Send + Sync {
     fn first_pdu_in_room(&self, room_id: &RoomId) -> Result<Option<Arc<PduEvent>>>;
-    fn last_timeline_count(&self, sender_user: &UserId, room_id: &RoomId) -> Result<u64>;
+    fn last_timeline_count(&self, sender_user: &UserId, room_id: &RoomId) -> Result<PduCount>;
 
     /// Returns the `count` of this pdu's id.
-    fn get_pdu_count(&self, event_id: &EventId) -> Result<Option<u64>>;
+    fn get_pdu_count(&self, event_id: &EventId) -> Result<Option<PduCount>>;
 
     /// Returns the json of a pdu.
     fn get_pdu_json(&self, event_id: &EventId) -> Result<Option<CanonicalJsonObject>>;
@@ -38,9 +40,6 @@ pub trait Data: Send + Sync {
     /// Returns the pdu as a `BTreeMap<String, CanonicalJsonValue>`.
     fn get_pdu_json_from_id(&self, pdu_id: &[u8]) -> Result<Option<CanonicalJsonObject>>;
 
-    /// Returns the `count` of this pdu's id.
-    fn pdu_count(&self, pdu_id: &[u8]) -> Result<u64>;
-
     /// Adds a new pdu to the timeline
     fn append_pdu(
         &self,
@@ -50,33 +49,34 @@ pub trait Data: Send + Sync {
         count: u64,
     ) -> Result<()>;
 
+    // Adds a new pdu to the backfilled timeline
+    fn prepend_backfill_pdu(
+        &self,
+        pdu_id: &[u8],
+        event_id: &EventId,
+        json: &CanonicalJsonObject,
+    ) -> Result<()>;
+
     /// Removes a pdu and creates a new one with the same id.
     fn replace_pdu(&self, pdu_id: &[u8], pdu: &PduEvent) -> Result<()>;
 
-    /// Returns an iterator over all events in a room that happened after the event with id `since`
-    /// in chronological order.
-    fn pdus_since<'a>(
-        &'a self,
-        user_id: &UserId,
-        room_id: &RoomId,
-        since: u64,
-    ) -> Result<Box<dyn Iterator<Item = Result<(Vec<u8>, PduEvent)>> + 'a>>;
-
     /// Returns an iterator over all events and their tokens in a room that happened before the
     /// event with id `until` in reverse-chronological order.
     fn pdus_until<'a>(
         &'a self,
         user_id: &UserId,
         room_id: &RoomId,
-        until: u64,
+        until: PduCount,
-    ) -> Result<Box<dyn Iterator<Item = Result<(Vec<u8>, PduEvent)>> + 'a>>;
+    ) -> Result<Box<dyn Iterator<Item = Result<(PduCount, PduEvent)>> + 'a>>;
 
+    /// Returns an iterator over all events in a room that happened after the event with id `from`
+    /// in chronological order.
     fn pdus_after<'a>(
         &'a self,
         user_id: &UserId,
         room_id: &RoomId,
-        from: u64,
+        from: PduCount,
-    ) -> Result<Box<dyn Iterator<Item = Result<(Vec<u8>, PduEvent)>> + 'a>>;
+    ) -> Result<Box<dyn Iterator<Item = Result<(PduCount, PduEvent)>> + 'a>>;
 
     fn increment_notification_counts(
         &self,

src/service/rooms/timeline/mod.rs

@@ -1,7 +1,9 @@
 mod data;
 
-use std::collections::HashMap;
+use std::cmp::Ordering;
+use std::collections::{BTreeMap, HashMap};
 
+use std::sync::RwLock;
 use std::{
     collections::HashSet,
     sync::{Arc, Mutex},
@@ -9,6 +11,8 @@ use std::{
 
 pub use data::Data;
 use regex::Regex;
+use ruma::api::federation;
+use ruma::serde::Base64;
 use ruma::{
     api::client::error::ErrorKind,
     canonical_json::to_canonical_value,
@@ -27,11 +31,13 @@ use ruma::{
     uint, CanonicalJsonObject, CanonicalJsonValue, EventId, OwnedEventId, OwnedRoomId,
     OwnedServerName, RoomAliasId, RoomId, UserId,
 };
+use ruma::{user_id, ServerName};
 use serde::Deserialize;
-use serde_json::value::to_raw_value;
+use serde_json::value::{to_raw_value, RawValue as RawJsonValue};
 use tokio::sync::MutexGuard;
-use tracing::{error, warn};
+use tracing::{error, info, warn};
 
+use crate::api::server_server;
 use crate::{
     service::pdu::{EventHash, PduBuilder},
     services, utils, Error, PduEvent, Result,
@@ -39,10 +45,70 @@ use crate::{
 
 use super::state_compressor::CompressedStateEvent;
 
+#[derive(Hash, PartialEq, Eq, Clone, Copy, Debug)]
+pub enum PduCount {
+    Backfilled(u64),
+    Normal(u64),
+}
+
+impl PduCount {
+    pub fn min() -> Self {
+        Self::Backfilled(u64::MAX)
+    }
+    pub fn max() -> Self {
+        Self::Normal(u64::MAX)
+    }
+
+    pub fn try_from_string(token: &str) -> Result<Self> {
+        if token.starts_with('-') {
+            token[1..].parse().map(PduCount::Backfilled)
+        } else {
+            token.parse().map(PduCount::Normal)
+        }
+        .map_err(|_| Error::BadRequest(ErrorKind::InvalidParam, "Invalid pagination token."))
+    }
+
+    pub fn stringify(&self) -> String {
+        match self {
+            PduCount::Backfilled(x) => format!("-{x}"),
+            PduCount::Normal(x) => x.to_string(),
+        }
+    }
+}
+
+impl PartialOrd for PduCount {
+    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+        Some(self.cmp(other))
+    }
+}
+
+impl Ord for PduCount {
+    fn cmp(&self, other: &Self) -> Ordering {
+        match (self, other) {
+            (PduCount::Normal(s), PduCount::Normal(o)) => s.cmp(o),
+            (PduCount::Backfilled(s), PduCount::Backfilled(o)) => o.cmp(s),
+            (PduCount::Normal(_), PduCount::Backfilled(_)) => Ordering::Greater,
+            (PduCount::Backfilled(_), PduCount::Normal(_)) => Ordering::Less,
+        }
+    }
+}
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn comparisons() {
+        assert!(PduCount::Normal(1) < PduCount::Normal(2));
+        assert!(PduCount::Backfilled(2) < PduCount::Backfilled(1));
+        assert!(PduCount::Normal(1) > PduCount::Backfilled(1));
+        assert!(PduCount::Backfilled(1) < PduCount::Normal(1));
+    }
+}
+
 pub struct Service {
     pub db: &'static dyn Data,
 
-    pub lasttimelinecount_cache: Mutex<HashMap<OwnedRoomId, u64>>,
+    pub lasttimelinecount_cache: Mutex<HashMap<OwnedRoomId, PduCount>>,
 }
 
 impl Service {
@@ -52,10 +118,15 @@ impl Service {
     }
 
     #[tracing::instrument(skip(self))]
-    pub fn last_timeline_count(&self, sender_user: &UserId, room_id: &RoomId) -> Result<u64> {
+    pub fn last_timeline_count(&self, sender_user: &UserId, room_id: &RoomId) -> Result<PduCount> {
         self.db.last_timeline_count(sender_user, room_id)
     }
 
+    /// Returns the `count` of this pdu's id.
+    pub fn get_pdu_count(&self, event_id: &EventId) -> Result<Option<PduCount>> {
+        self.db.get_pdu_count(event_id)
+    }
+
     // TODO Is this the same as the function above?
     /*
     #[tracing::instrument(skip(self))]
@@ -79,11 +150,6 @@ impl Service {
     }
     */
 
-    /// Returns the `count` of this pdu's id.
-    pub fn get_pdu_count(&self, event_id: &EventId) -> Result<Option<u64>> {
-        self.db.get_pdu_count(event_id)
-    }
-
     /// Returns the json of a pdu.
     pub fn get_pdu_json(&self, event_id: &EventId) -> Result<Option<CanonicalJsonObject>> {
         self.db.get_pdu_json(event_id)
@@ -128,11 +194,6 @@ impl Service {
         self.db.get_pdu_json_from_id(pdu_id)
     }
 
-    /// Returns the `count` of this pdu's id.
-    pub fn pdu_count(&self, pdu_id: &[u8]) -> Result<u64> {
-        self.db.pdu_count(pdu_id)
-    }
-
     /// Removes a pdu and creates a new one with the same id.
     #[tracing::instrument(skip(self))]
     fn replace_pdu(&self, pdu_id: &[u8], pdu: &PduEvent) -> Result<()> {
@@ -863,19 +924,8 @@ impl Service {
         &'a self,
         user_id: &UserId,
         room_id: &RoomId,
-    ) -> Result<impl Iterator<Item = Result<(Vec<u8>, PduEvent)>> + 'a> {
+    ) -> Result<impl Iterator<Item = Result<(PduCount, PduEvent)>> + 'a> {
-        self.pdus_since(user_id, room_id, 0)
+        self.pdus_after(user_id, room_id, PduCount::min())
-    }
-
-    /// Returns an iterator over all events in a room that happened after the event with id `since`
-    /// in chronological order.
-    pub fn pdus_since<'a>(
-        &'a self,
-        user_id: &UserId,
-        room_id: &RoomId,
-        since: u64,
-    ) -> Result<impl Iterator<Item = Result<(Vec<u8>, PduEvent)>> + 'a> {
-        self.db.pdus_since(user_id, room_id, since)
     }
 
     /// Returns an iterator over all events and their tokens in a room that happened before the
@@ -885,8 +935,8 @@ impl Service {
         &'a self,
         user_id: &UserId,
         room_id: &RoomId,
-        until: u64,
+        until: PduCount,
-    ) -> Result<impl Iterator<Item = Result<(Vec<u8>, PduEvent)>> + 'a> {
+    ) -> Result<impl Iterator<Item = Result<(PduCount, PduEvent)>> + 'a> {
         self.db.pdus_until(user_id, room_id, until)
     }
 
@@ -897,8 +947,8 @@ impl Service {
         &'a self,
         user_id: &UserId,
         room_id: &RoomId,
-        from: u64,
+        from: PduCount,
-    ) -> Result<impl Iterator<Item = Result<(Vec<u8>, PduEvent)>> + 'a> {
+    ) -> Result<impl Iterator<Item = Result<(PduCount, PduEvent)>> + 'a> {
         self.db.pdus_after(user_id, room_id, from)
     }
 
@@ -915,4 +965,118 @@ impl Service {
         // If event does not exist, just noop
         Ok(())
     }
+
+    #[tracing::instrument(skip(self, room_id))]
+    pub async fn backfill_if_required(&self, room_id: &RoomId, from: PduCount) -> Result<()> {
+        let first_pdu = self
+            .all_pdus(&user_id!("@doesntmatter:conduit.rs"), &room_id)?
+            .next()
+            .expect("Room is not empty")?;
+
+        if first_pdu.0 < from {
+            // No backfill required, there are still events between them
+            return Ok(());
+        }
+
+        let power_levels: RoomPowerLevelsEventContent = services()
+            .rooms
+            .state_accessor
+            .room_state_get(&room_id, &StateEventType::RoomPowerLevels, "")?
+            .map(|ev| {
+                serde_json::from_str(ev.content.get())
+                    .map_err(|_| Error::bad_database("invalid m.room.power_levels event"))
+            })
+            .transpose()?
+            .unwrap_or_default();
+        let mut admin_servers = power_levels
+            .users
+            .iter()
+            .filter(|(_, level)| **level > power_levels.users_default)
+            .map(|(user_id, _)| user_id.server_name())
+            .collect::<HashSet<_>>();
+        admin_servers.remove(services().globals.server_name());
+
+        // Request backfill
+        for backfill_server in admin_servers {
+            info!("Asking {backfill_server} for backfill");
+            let response = services()
+                .sending
+                .send_federation_request(
+                    backfill_server,
+                    federation::backfill::get_backfill::v1::Request {
+                        room_id: room_id.to_owned(),
+                        v: vec![first_pdu.1.event_id.as_ref().to_owned()],
+                        limit: uint!(100),
+                    },
+                )
+                .await;
+            match response {
+                Ok(response) => {
+                    let mut pub_key_map = RwLock::new(BTreeMap::new());
+                    for pdu in response.pdus {
+                        if let Err(e) = self
+                            .backfill_pdu(backfill_server, pdu, &mut pub_key_map)
+                            .await
+                        {
+                            warn!("Failed to add backfilled pdu: {e}");
+                        }
+                    }
+                    return Ok(());
+                }
+                Err(e) => {
+                    warn!("{backfill_server} could not provide backfill: {e}");
+                }
+            }
+        }
+
+        info!("No servers could backfill");
+        Ok(())
+    }
+
+    #[tracing::instrument(skip(self, pdu))]
+    pub async fn backfill_pdu(
+        &self,
+        origin: &ServerName,
+        pdu: Box<RawJsonValue>,
+        pub_key_map: &RwLock<BTreeMap<String, BTreeMap<String, Base64>>>,
+    ) -> Result<()> {
+        let (event_id, value, room_id) = server_server::parse_incoming_pdu(&pdu)?;
+
+        services()
+            .rooms
+            .event_handler
+            .handle_incoming_pdu(origin, &event_id, &room_id, value, false, &pub_key_map)
+            .await?;
+
+        let value = self.get_pdu_json(&event_id)?.expect("We just created it");
+
+        let shortroomid = services()
+            .rooms
+            .short
+            .get_shortroomid(&room_id)?
+            .expect("room exists");
+
+        let mutex_insert = Arc::clone(
+            services()
+                .globals
+                .roomid_mutex_insert
+                .write()
+                .unwrap()
+                .entry(room_id.clone())
+                .or_default(),
+        );
+        let insert_lock = mutex_insert.lock().unwrap();
+
+        let count = services().globals.next_count()?;
+        let mut pdu_id = shortroomid.to_be_bytes().to_vec();
+        pdu_id.extend_from_slice(&count.to_be_bytes());
+
+        // Insert pdu
+        self.db.prepend_backfill_pdu(&pdu_id, &event_id, &value)?;
+
+        drop(insert_lock);
+
+        info!("Appended incoming pdu");
+        Ok(())
+    }
 }