Revert "remove synchronous federation"

This reverts commit 2767ab4a6f.

api_tests/run-federation-test.sh

@@ -2,6 +2,7 @@
 set -e
 
 export LEMMY_DATABASE_URL=postgres://lemmy:password@localhost:5432
+export LEMMY_SYNCHRONOUS_FEDERATION=1 # currently this is true in debug by default, but still.
 pushd ..
 cargo build
 rm target/lemmy_server || true

crates/api_common/src/send_activity.rs

@@ -17,14 +17,22 @@ use lemmy_db_schema::{
   },
 };
 use lemmy_db_views::structs::PrivateMessageView;
-use lemmy_utils::error::LemmyResult;
+use lemmy_utils::{error::LemmyResult, SYNCHRONOUS_FEDERATION};
-use once_cell::sync::OnceCell;
+use once_cell::sync::{Lazy, OnceCell};
+use tokio::{
+  sync::{
+    mpsc,
+    mpsc::{UnboundedReceiver, UnboundedSender, WeakUnboundedSender},
+    Mutex,
+  },
+  task::JoinHandle,
+};
 use url::Url;
 
 type MatchOutgoingActivitiesBoxed =
   Box<for<'a> fn(SendActivityData, &'a Data<LemmyContext>) -> BoxFuture<'a, LemmyResult<()>>>;
 
-/// This static is necessary so that the api_common crates don't need to depend on lemmy_apub
+/// This static is necessary so that activities can be sent out synchronously for tests and the api_common crates don't need to depend on lemmy_apub
 pub static MATCH_OUTGOING_ACTIVITIES: OnceCell<MatchOutgoingActivitiesBoxed> = OnceCell::new();
 
 #[derive(Debug)]
@@ -54,16 +62,51 @@ pub enum SendActivityData {
   CreateReport(Url, Person, Community, String),
 }
 
-pub struct ActivityChannel;
+// TODO: instead of static, move this into LemmyContext. make sure that stopping the process with
+//       ctrl+c still works.
+static ACTIVITY_CHANNEL: Lazy<ActivityChannel> = Lazy::new(|| {
+  let (sender, receiver) = mpsc::unbounded_channel();
+  let weak_sender = sender.downgrade();
+  ActivityChannel {
+    weak_sender,
+    receiver: Mutex::new(receiver),
+    keepalive_sender: Mutex::new(Some(sender)),
+  }
+});
+
+pub struct ActivityChannel {
+  weak_sender: WeakUnboundedSender<SendActivityData>,
+  receiver: Mutex<UnboundedReceiver<SendActivityData>>,
+  keepalive_sender: Mutex<Option<UnboundedSender<SendActivityData>>>,
+}
 
 impl ActivityChannel {
+  pub async fn retrieve_activity() -> Option<SendActivityData> {
+    let mut lock = ACTIVITY_CHANNEL.receiver.lock().await;
+    lock.recv().await
+  }
+
   pub async fn submit_activity(
     data: SendActivityData,
     context: &Data<LemmyContext>,
   ) -> LemmyResult<()> {
+    if *SYNCHRONOUS_FEDERATION {
       MATCH_OUTGOING_ACTIVITIES
         .get()
         .expect("retrieve function pointer")(data, context)
-    .await
+      .await?;
+    }
+    // could do `ACTIVITY_CHANNEL.keepalive_sender.lock()` instead and get rid of weak_sender,
+    // not sure which way is more efficient
+    else if let Some(sender) = ACTIVITY_CHANNEL.weak_sender.upgrade() {
+      sender.send(data)?;
+    }
+    Ok(())
+  }
+
+  pub async fn close(outgoing_activities_task: JoinHandle<LemmyResult<()>>) -> LemmyResult<()> {
+    ACTIVITY_CHANNEL.keepalive_sender.lock().await.take();
+    outgoing_activities_task.await??;
+    Ok(())
   }
 }

crates/api_crud/src/post/create.rs

@@ -37,6 +37,7 @@ use lemmy_utils::{
     slurs::{check_slurs, check_slurs_opt},
     validation::{check_url_scheme, clean_url_params, is_valid_body_field, is_valid_post_title},
   },
+  SYNCHRONOUS_FEDERATION,
 };
 use tracing::Instrument;
 use url::Url;
@@ -189,7 +190,11 @@ pub async fn create_post(
         Err(e) => Err(e).with_lemmy_type(LemmyErrorType::CouldntSendWebmention),
       }
     };
+    if *SYNCHRONOUS_FEDERATION {
+      task.await?;
+    } else {
       spawn_try_task(task);
+    }
   };
 
   build_post_response(&context, community_id, person_id, post_id).await

crates/apub/src/activities/mod.rs

@@ -45,6 +45,7 @@ use lemmy_db_views_actor::structs::{CommunityPersonBanView, CommunityView};
 use lemmy_utils::{
   error::{LemmyError, LemmyErrorExt, LemmyErrorType, LemmyResult},
   spawn_try_task,
+  SYNCHRONOUS_FEDERATION,
 };
 use serde::Serialize;
 use std::{ops::Deref, time::Duration};
@@ -220,6 +221,13 @@ where
   Ok(())
 }
 
+pub async fn handle_outgoing_activities(context: Data<LemmyContext>) -> LemmyResult<()> {
+  while let Some(data) = ActivityChannel::retrieve_activity().await {
+    match_outgoing_activities(data, &context.reset_request_count()).await?
+  }
+  Ok(())
+}
+
 pub async fn match_outgoing_activities(
   data: SendActivityData,
   context: &Data<LemmyContext>,
@@ -324,6 +332,10 @@ pub async fn match_outgoing_activities(
       }
     }
   };
+  if *SYNCHRONOUS_FEDERATION {
+    fed_task.await?;
+  } else {
     spawn_try_task(fed_task);
+  }
   Ok(())
 }

crates/utils/src/lib.rs

@@ -18,6 +18,7 @@ pub mod version;
 
 use error::LemmyError;
 use futures::Future;
+use once_cell::sync::Lazy;
 use std::time::Duration;
 use tracing::Instrument;
 
@@ -37,6 +38,16 @@ macro_rules! location_info {
   };
 }
 
+/// if true, all federation should happen synchronously. useful for debugging and testing.
+/// defaults to true on debug mode, false on releasemode
+/// override to true by setting env LEMMY_SYNCHRONOUS_FEDERATION=1
+/// override to false by setting env LEMMY_SYNCHRONOUS_FEDERATION=""
+pub static SYNCHRONOUS_FEDERATION: Lazy<bool> = Lazy::new(|| {
+  std::env::var("LEMMY_SYNCHRONOUS_FEDERATION")
+    .map(|s| !s.is_empty())
+    .unwrap_or(cfg!(debug_assertions))
+});
+
 /// tokio::spawn, but accepts a future that may fail and also
 /// * logs errors
 /// * attaches the spawned task to the tracing span of the caller for better logging

src/lib.rs

@@ -28,14 +28,14 @@ use lemmy_api_common::{
   context::LemmyContext,
   lemmy_db_views::structs::SiteView,
   request::build_user_agent,
-  send_activity::MATCH_OUTGOING_ACTIVITIES,
+  send_activity::{ActivityChannel, MATCH_OUTGOING_ACTIVITIES},
   utils::{
     check_private_instance_and_federation_enabled,
     local_site_rate_limit_to_rate_limit_config,
   },
 };
 use lemmy_apub::{
-  activities::match_outgoing_activities,
+  activities::{handle_outgoing_activities, match_outgoing_activities},
   VerifyUrlData,
   FEDERATION_HTTP_FETCH_LIMIT,
 };
@@ -203,6 +203,8 @@ pub async fn start_lemmy_server(args: CmdArgs) -> Result<(), LemmyError> {
       Box::pin(match_outgoing_activities(d, c))
     }))
     .expect("set function pointer");
+  let request_data = federation_config.to_request_data();
+  let outgoing_activities_task = tokio::task::spawn(handle_outgoing_activities(request_data));
 
   let server = if args.http_server {
     Some(create_http_server(
@@ -245,6 +247,9 @@ pub async fn start_lemmy_server(args: CmdArgs) -> Result<(), LemmyError> {
     federate.cancel().await?;
   }
 
+  // Wait for outgoing apub sends to complete
+  ActivityChannel::close(outgoing_activities_task).await?;
+
   Ok(())
 }