p2p: WIP implement rpc server for the p2p monitor

5 files changed, 391 insertions, 238 deletions

diff --git a/p2p/examples/monitor/Cargo.lock b/p2p/examples/monitor/Cargo.lock
index d881b93..25defa2 100644
--- a/p2p/examples/monitor/Cargo.lock
+++ b/p2p/examples/monitor/Cargo.lock
@@ -931,12 +931,28 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "42703706b716c37f96a77aea830392ad231f44c9e9a67872fa5548707e11b11c"
 
 [[package]]
+name = "futures"
+version = "0.3.30"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "645c6916888f6cb6350d2550b80fb63e734897a8498abe35cfb732b6487804b0"
+dependencies = [
+ "futures-channel",
+ "futures-core",
+ "futures-executor",
+ "futures-io",
+ "futures-sink",
+ "futures-task",
+ "futures-util",
+]
+
+[[package]]
 name = "futures-channel"
 version = "0.3.30"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "eac8f7d7865dcb88bd4373ab671c8cf4508703796caa2b1985a9ca867b3fcb78"
 dependencies = [
  "futures-core",
+ "futures-sink",
 ]
 
 [[package]]
@@ -946,6 +962,17 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "dfc6580bb841c5a68e9ef15c77ccc837b40a7504914d52e47b8b0e9bbda25a1d"
 
 [[package]]
+name = "futures-executor"
+version = "0.3.30"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a576fc72ae164fca6b9db127eaa9a9dda0d61316034f33a0a0d4eda41f02b01d"
+dependencies = [
+ "futures-core",
+ "futures-task",
+ "futures-util",
+]
+
+[[package]]
 name = "futures-io"
 version = "0.3.30"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -980,6 +1007,17 @@ dependencies = [
 ]
 
 [[package]]
+name = "futures-macro"
+version = "0.3.30"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "87750cf4b7a4c0625b1529e4c543c2182106e4dedc60a2a6455e00d212c489ac"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn 2.0.66",
+]
+
+[[package]]
 name = "futures-rustls"
 version = "0.25.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -1008,9 +1046,13 @@ version = "0.3.30"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "3d6401deb83407ab3da39eba7e33987a73c3df0c82b4bb5813ee871c19c41d48"
 dependencies = [
+ "futures-channel",
  "futures-core",
+ "futures-io",
+ "futures-macro",
  "futures-sink",
  "futures-task",
+ "memchr",
  "pin-project-lite",
  "pin-utils",
  "slab",
@@ -1386,6 +1428,7 @@ dependencies = [
  "ctrlc",
  "easy-parallel",
  "env_logger",
+ "futures",
  "karyon_core",
  "karyon_jsonrpc",
  "karyon_p2p",
diff --git a/p2p/examples/monitor/Cargo.toml b/p2p/examples/monitor/Cargo.toml
index b323ed1..52bab15 100644
--- a/p2p/examples/monitor/Cargo.toml
+++ b/p2p/examples/monitor/Cargo.toml
@@ -18,6 +18,7 @@ smol = "2.0.0"
 serde_json = "1.0.117"
 easy-parallel = "3.3.1"
 ringbuffer = "0.15.0"
+futures = "0.3.30"
 
 [[bin]]
 name = "client"
diff --git a/p2p/examples/monitor/src/client.rs b/p2p/examples/monitor/src/client.rs
index b81c286..2f4d00d 100644
--- a/p2p/examples/monitor/src/client.rs
+++ b/p2p/examples/monitor/src/client.rs
@@ -1,4 +1,5 @@
 use clap::Parser;
+use serde::{Deserialize, Serialize};
 
 use karyon_jsonrpc::Client;
 use karyon_p2p::endpoint::Endpoint;
@@ -11,6 +12,9 @@ struct Cli {
     rpc_endpoint: Endpoint,
 }
 
+#[derive(Deserialize, Serialize)]
+struct Pong {}
+
 fn main() {
     smol::block_on(async {
         env_logger::init();
@@ -32,18 +36,44 @@ fn main() {
             .await
             .expect("Subscribe to peer pool events");
 
+        let (_, sub3) = rpc
+            .subscribe("MonitorRPC.discovery_subscribe", ())
+            .await
+            .expect("Subscribe to discovery events");
+
+        smol::spawn(async move {
+            loop {
+                let event = sub.recv().await.expect("Receive connection event");
+                println!("Receive new connection event: {event}");
+            }
+        })
+        .detach();
+
         smol::spawn(async move {
             loop {
-                let _event = sub.recv().await.expect("Receive connection event");
+                let event = sub2.recv().await.expect("Receive peer pool event");
+                println!("Receive new peerpool event: {event}");
             }
         })
         .detach();
 
         smol::spawn(async move {
             loop {
-                let _event = sub2.recv().await.expect("Receive peer pool event");
+                let event = sub3.recv().await.expect("Receive discovery event");
+                println!("Receive new discovery event: {event}");
             }
         })
-        .await;
+        .detach();
+
+        // start ping-pong loop
+        loop {
+            smol::Timer::after(std::time::Duration::from_secs(1)).await;
+            let _: Pong = rpc
+                .call("MonitorRPC.ping", ())
+                .await
+                .expect("Receive pong message");
+
+            println!("Receive pong message");
+        }
     });
 }
diff --git a/p2p/examples/monitor/src/main.rs b/p2p/examples/monitor/src/main.rs
index c57d06c..990f8d2 100644
--- a/p2p/examples/monitor/src/main.rs
+++ b/p2p/examples/monitor/src/main.rs
@@ -1,28 +1,21 @@
+mod service;
 mod shared;
 
 use std::sync::Arc;
 
 use clap::Parser;
-use log::error;
-use ringbuffer::{AllocRingBuffer, RingBuffer};
-use serde::{Deserialize, Serialize};
-use smol::{channel, lock::Mutex, Executor};
+use smol::{channel, Executor};
 
-use karyon_core::async_util::{CondWait, TaskGroup, TaskResult};
-use karyon_jsonrpc::{
-    message::SubscriptionID, rpc_impl, rpc_pubsub_impl, Channel, Server, Subscription,
-};
+use karyon_jsonrpc::Server;
 use karyon_p2p::{
     endpoint::{Endpoint, Port},
     keypair::{KeyPair, KeyPairType},
-    monitor::{ConnEvent, DiscoveryEvent, PeerPoolEvent},
-    ArcBackend, Backend, Config, Error, Result,
+    Backend, Config,
 };
 
+use service::MonitorRPC;
 use shared::run_executor;
 
-const EVENT_BUFFER_SIZE: usize = 30;
-
 #[derive(Parser)]
 #[command(author, version, about, long_about = None)]
 struct Cli {
@@ -47,202 +40,6 @@ struct Cli {
     discovery_port: Option<Port>,
 }
 
-struct MonitorRPC {
-    backend: ArcBackend,
-    conn_event_buffer: Arc<Mutex<AllocRingBuffer<ConnEvent>>>,
-    pp_event_buffer: Arc<Mutex<AllocRingBuffer<PeerPoolEvent>>>,
-    discv_event_buffer: Arc<Mutex<AllocRingBuffer<DiscoveryEvent>>>,
-    conn_event_condvar: Arc<CondWait>,
-    pp_event_condvar: Arc<CondWait>,
-    discv_event_condvar: Arc<CondWait>,
-    task_group: TaskGroup,
-}
-
-impl MonitorRPC {
-    fn new(backend: ArcBackend, ex: Arc<Executor<'static>>) -> Arc<Self> {
-        Arc::new(MonitorRPC {
-            backend,
-            conn_event_buffer: Arc::new(Mutex::new(AllocRingBuffer::new(EVENT_BUFFER_SIZE))),
-            pp_event_buffer: Arc::new(Mutex::new(AllocRingBuffer::new(EVENT_BUFFER_SIZE))),
-            discv_event_buffer: Arc::new(Mutex::new(AllocRingBuffer::new(EVENT_BUFFER_SIZE))),
-            conn_event_condvar: Arc::new(CondWait::new()),
-            pp_event_condvar: Arc::new(CondWait::new()),
-            discv_event_condvar: Arc::new(CondWait::new()),
-            task_group: TaskGroup::with_executor(ex.into()),
-        })
-    }
-
-    async fn run(&self) -> Result<()> {
-        let conn_events = self.backend.monitor().conn_events().await;
-        let peer_pool_events = self.backend.monitor().peer_pool_events().await;
-        let discovery_events = self.backend.monitor().discovery_events().await;
-
-        let conn_event_buffer = self.conn_event_buffer.clone();
-        let pp_event_buffer = self.pp_event_buffer.clone();
-        let discv_event_buffer = self.discv_event_buffer.clone();
-
-        let conn_event_condvar = self.conn_event_condvar.clone();
-        let pp_event_condvar = self.pp_event_condvar.clone();
-        let discv_event_condvar = self.discv_event_condvar.clone();
-
-        let on_failuer = |res: TaskResult<Result<()>>| async move {
-            if let TaskResult::Completed(Err(err)) = res {
-                error!("Event receive loop: {err}")
-            }
-        };
-
-        self.task_group.spawn(
-            async move {
-                loop {
-                    let event = conn_events.recv().await?;
-                    conn_event_buffer.lock().await.push(event);
-                    conn_event_condvar.broadcast().await;
-                }
-            },
-            on_failuer,
-        );
-
-        self.task_group.spawn(
-            async move {
-                loop {
-                    let event = peer_pool_events.recv().await?;
-                    pp_event_buffer.lock().await.push(event);
-                    pp_event_condvar.broadcast().await;
-                }
-            },
-            on_failuer,
-        );
-
-        self.task_group.spawn(
-            async move {
-                loop {
-                    let event = discovery_events.recv().await?;
-                    discv_event_buffer.lock().await.push(event);
-                    discv_event_condvar.broadcast().await;
-                }
-            },
-            on_failuer,
-        );
-
-        Ok(())
-    }
-
-    async fn shutdown(&self) {
-        self.task_group.cancel().await;
-    }
-}
-
-#[rpc_impl]
-impl MonitorRPC {
-    async fn peer_id(
-        &self,
-        _params: serde_json::Value,
-    ) -> karyon_jsonrpc::Result<serde_json::Value> {
-        Ok(serde_json::json!(self.backend.peer_id().to_string()))
-    }
-
-    async fn inbound_connection(
-        &self,
-        _params: serde_json::Value,
-    ) -> karyon_jsonrpc::Result<serde_json::Value> {
-        Ok(serde_json::json!(self.backend.inbound_slots()))
-    }
-
-    async fn outbound_connection(
-        &self,
-        _params: serde_json::Value,
-    ) -> karyon_jsonrpc::Result<serde_json::Value> {
-        Ok(serde_json::json!(self.backend.outbound_slots()))
-    }
-}
-
-#[rpc_pubsub_impl]
-impl MonitorRPC {
-    async fn conn_subscribe(
-        &self,
-        chan: Arc<Channel>,
-        method: String,
-        _params: serde_json::Value,
-    ) -> karyon_jsonrpc::Result<serde_json::Value> {
-        let sub = chan.new_subscription(&method).await;
-        let sub_id = sub.id;
-
-        let cond_wait = self.conn_event_condvar.clone();
-        let buffer = self.conn_event_buffer.clone();
-        self.task_group
-            .spawn(notify(sub, cond_wait, buffer), notify_failed);
-
-        Ok(serde_json::json!(sub_id))
-    }
-
-    async fn peer_pool_subscribe(
-        &self,
-        chan: Arc<Channel>,
-        method: String,
-        _params: serde_json::Value,
-    ) -> karyon_jsonrpc::Result<serde_json::Value> {
-        let sub = chan.new_subscription(&method).await;
-        let sub_id = sub.id;
-
-        let cond_wait = self.pp_event_condvar.clone();
-        let buffer = self.pp_event_buffer.clone();
-        self.task_group
-            .spawn(notify(sub, cond_wait, buffer), notify_failed);
-
-        Ok(serde_json::json!(sub_id))
-    }
-
-    async fn discovery_subscribe(
-        &self,
-        chan: Arc<Channel>,
-        method: String,
-        _params: serde_json::Value,
-    ) -> karyon_jsonrpc::Result<serde_json::Value> {
-        let sub = chan.new_subscription(&method).await;
-        let sub_id = sub.id;
-
-        let cond_wait = self.discv_event_condvar.clone();
-        let buffer = self.discv_event_buffer.clone();
-        self.task_group
-            .spawn(notify(sub, cond_wait, buffer), notify_failed);
-
-        Ok(serde_json::json!(sub_id))
-    }
-
-    async fn conn_unsubscribe(
-        &self,
-        chan: Arc<Channel>,
-        _method: String,
-        params: serde_json::Value,
-    ) -> karyon_jsonrpc::Result<serde_json::Value> {
-        let sub_id: SubscriptionID = serde_json::from_value(params)?;
-        chan.remove_subscription(&sub_id).await;
-        Ok(serde_json::json!(true))
-    }
-
-    async fn peer_pool_unsubscribe(
-        &self,
-        chan: Arc<Channel>,
-        _method: String,
-        params: serde_json::Value,
-    ) -> karyon_jsonrpc::Result<serde_json::Value> {
-        let sub_id: SubscriptionID = serde_json::from_value(params)?;
-        chan.remove_subscription(&sub_id).await;
-        Ok(serde_json::json!(true))
-    }
-
-    async fn discovery_unsubscribe(
-        &self,
-        chan: Arc<Channel>,
-        _method: String,
-        params: serde_json::Value,
-    ) -> karyon_jsonrpc::Result<serde_json::Value> {
-        let sub_id: SubscriptionID = serde_json::from_value(params)?;
-        chan.remove_subscription(&sub_id).await;
-        Ok(serde_json::json!(true))
-    }
-}
-
 fn main() {
     env_logger::init();
 
@@ -309,30 +106,3 @@ fn main() {
         ex,
     );
 }
-
-async fn notify<T: Serialize + Deserialize<'static> + Clone>(
-    sub: Subscription,
-    cond_wait: Arc<CondWait>,
-    buffer: Arc<Mutex<AllocRingBuffer<T>>>,
-) -> Result<()> {
-    for event in buffer.lock().await.iter() {
-        if let Err(err) = sub.notify(serde_json::json!(event)).await {
-            return Err(Error::Other(format!("failed to notify: {err}")));
-        }
-    }
-    loop {
-        cond_wait.wait().await;
-        cond_wait.reset().await;
-        if let Some(event) = buffer.lock().await.back().cloned() {
-            if let Err(err) = sub.notify(serde_json::json!(event)).await {
-                return Err(Error::Other(format!("failed to notify: {err}")));
-            }
-        }
-    }
-}
-
-async fn notify_failed(result: TaskResult<Result<()>>) {
-    if let TaskResult::Completed(Err(err)) = result {
-        error!("Error: {err}");
-    }
-}
diff --git a/p2p/examples/monitor/src/service.rs b/p2p/examples/monitor/src/service.rs
new file mode 100644
index 0000000..15ce8da
--- /dev/null
+++ b/p2p/examples/monitor/src/service.rs
@@ -0,0 +1,309 @@
+use std::{collections::HashMap, sync::Arc};
+
+use futures::stream::{FuturesUnordered, StreamExt};
+use log::{debug, error};
+use ringbuffer::{AllocRingBuffer, RingBuffer};
+use serde::{Deserialize, Serialize};
+use smol::{lock::Mutex, Executor};
+
+use karyon_core::async_util::{TaskGroup, TaskResult};
+use karyon_jsonrpc::{message::SubscriptionID, rpc_impl, rpc_pubsub_impl, Channel, Subscription};
+use karyon_p2p::{monitor::MonitorTopic, ArcBackend, Result};
+
+const EVENT_BUFFER_SIZE: usize = 60;
+
+pub struct MonitorRPC {
+    backend: ArcBackend,
+    subs: Arc<Subscriptions>,
+    task_group: TaskGroup,
+}
+
+impl MonitorRPC {
+    pub fn new(backend: ArcBackend, ex: Arc<Executor<'static>>) -> Arc<Self> {
+        Arc::new(MonitorRPC {
+            backend,
+            task_group: TaskGroup::with_executor(ex.clone().into()),
+            subs: Subscriptions::new(ex),
+        })
+    }
+
+    pub async fn run(self: &Arc<Self>) -> Result<()> {
+        let conn_events = self.backend.monitor().conn_events().await;
+        let peer_pool_events = self.backend.monitor().peer_pool_events().await;
+        let discovery_events = self.backend.monitor().discovery_events().await;
+
+        let on_failuer = |res: TaskResult<Result<()>>| async move {
+            if let TaskResult::Completed(Err(err)) = res {
+                error!("Event receive loop: {err}")
+            }
+        };
+
+        let selfc = self.clone();
+        self.task_group.spawn(
+            async move {
+                loop {
+                    let event = conn_events.recv().await?;
+                    selfc.subs.notify(MonitorTopic::Conn, event).await;
+                }
+            },
+            on_failuer,
+        );
+
+        let selfc = self.clone();
+        self.task_group.spawn(
+            async move {
+                loop {
+                    let event = peer_pool_events.recv().await?;
+                    selfc.subs.notify(MonitorTopic::PeerPool, event).await;
+                }
+            },
+            on_failuer,
+        );
+
+        let selfc = self.clone();
+        self.task_group.spawn(
+            async move {
+                loop {
+                    let event = discovery_events.recv().await?;
+                    selfc.subs.notify(MonitorTopic::Discovery, event).await;
+                }
+            },
+            on_failuer,
+        );
+
+        Ok(())
+    }
+
+    pub async fn shutdown(&self) {
+        self.task_group.cancel().await;
+        self.subs.stop().await;
+    }
+}
+
+#[rpc_impl]
+impl MonitorRPC {
+    pub async fn ping(
+        &self,
+        _params: serde_json::Value,
+    ) -> karyon_jsonrpc::Result<serde_json::Value> {
+        Ok(serde_json::json!(Pong {}))
+    }
+
+    pub async fn peer_id(
+        &self,
+        _params: serde_json::Value,
+    ) -> karyon_jsonrpc::Result<serde_json::Value> {
+        Ok(serde_json::json!(self.backend.peer_id().to_string()))
+    }
+
+    pub async fn inbound_connection(
+        &self,
+        _params: serde_json::Value,
+    ) -> karyon_jsonrpc::Result<serde_json::Value> {
+        Ok(serde_json::json!(self.backend.inbound_slots()))
+    }
+
+    pub async fn outbound_connection(
+        &self,
+        _params: serde_json::Value,
+    ) -> karyon_jsonrpc::Result<serde_json::Value> {
+        Ok(serde_json::json!(self.backend.outbound_slots()))
+    }
+}
+
+#[rpc_pubsub_impl]
+impl MonitorRPC {
+    pub async fn conn_subscribe(
+        &self,
+        chan: Arc<Channel>,
+        method: String,
+        _params: serde_json::Value,
+    ) -> karyon_jsonrpc::Result<serde_json::Value> {
+        let sub = chan.new_subscription(&method).await;
+        let sub_id = sub.id;
+
+        self.subs.add(MonitorTopic::Conn, sub).await;
+
+        Ok(serde_json::json!(sub_id))
+    }
+
+    pub async fn peer_pool_subscribe(
+        &self,
+        chan: Arc<Channel>,
+        method: String,
+        _params: serde_json::Value,
+    ) -> karyon_jsonrpc::Result<serde_json::Value> {
+        let sub = chan.new_subscription(&method).await;
+        let sub_id = sub.id;
+
+        self.subs.add(MonitorTopic::PeerPool, sub).await;
+
+        Ok(serde_json::json!(sub_id))
+    }
+
+    pub async fn discovery_subscribe(
+        &self,
+        chan: Arc<Channel>,
+        method: String,
+        _params: serde_json::Value,
+    ) -> karyon_jsonrpc::Result<serde_json::Value> {
+        let sub = chan.new_subscription(&method).await;
+        let sub_id = sub.id;
+
+        self.subs.add(MonitorTopic::Discovery, sub).await;
+
+        Ok(serde_json::json!(sub_id))
+    }
+
+    pub async fn conn_unsubscribe(
+        &self,
+        chan: Arc<Channel>,
+        _method: String,
+        params: serde_json::Value,
+    ) -> karyon_jsonrpc::Result<serde_json::Value> {
+        let sub_id: SubscriptionID = serde_json::from_value(params)?;
+        chan.remove_subscription(&sub_id).await;
+        Ok(serde_json::json!(true))
+    }
+
+    pub async fn peer_pool_unsubscribe(
+        &self,
+        chan: Arc<Channel>,
+        _method: String,
+        params: serde_json::Value,
+    ) -> karyon_jsonrpc::Result<serde_json::Value> {
+        let sub_id: SubscriptionID = serde_json::from_value(params)?;
+        chan.remove_subscription(&sub_id).await;
+        Ok(serde_json::json!(true))
+    }
+
+    pub async fn discovery_unsubscribe(
+        &self,
+        chan: Arc<Channel>,
+        _method: String,
+        params: serde_json::Value,
+    ) -> karyon_jsonrpc::Result<serde_json::Value> {
+        let sub_id: SubscriptionID = serde_json::from_value(params)?;
+        chan.remove_subscription(&sub_id).await;
+        Ok(serde_json::json!(true))
+    }
+}
+
+#[derive(Deserialize, Serialize)]
+struct Pong {}
+
+struct Subscriptions {
+    subs: Mutex<HashMap<MonitorTopic, HashMap<SubscriptionID, Subscription>>>,
+    buffer: Mutex<HashMap<MonitorTopic, AllocRingBuffer<serde_json::Value>>>,
+    task_group: TaskGroup,
+}
+
+impl Subscriptions {
+    fn new(ex: Arc<Executor<'static>>) -> Arc<Self> {
+        let mut subs = HashMap::new();
+        subs.insert(MonitorTopic::Conn, HashMap::new());
+        subs.insert(MonitorTopic::PeerPool, HashMap::new());
+        subs.insert(MonitorTopic::Discovery, HashMap::new());
+
+        let mut buffer = HashMap::new();
+        buffer.insert(MonitorTopic::Conn, AllocRingBuffer::new(EVENT_BUFFER_SIZE));
+        buffer.insert(
+            MonitorTopic::PeerPool,
+            AllocRingBuffer::new(EVENT_BUFFER_SIZE),
+        );
+        buffer.insert(
+            MonitorTopic::Discovery,
+            AllocRingBuffer::new(EVENT_BUFFER_SIZE),
+        );
+
+        Arc::new(Self {
+            subs: Mutex::new(subs),
+            buffer: Mutex::new(buffer),
+            task_group: TaskGroup::with_executor(ex.into()),
+        })
+    }
+
+    /// Adds the subscription to the subs map according to the given type
+    async fn add(self: &Arc<Self>, ty: MonitorTopic, sub: Subscription) {
+        match self.subs.lock().await.get_mut(&ty) {
+            Some(subs) => {
+                subs.insert(sub.id, sub.clone());
+            }
+            None => todo!(),
+        }
+        // Send old events in the buffer to the subscriber
+        self.send_old_events(ty, sub).await;
+    }
+
+    /// Notifies all subscribers   
+    async fn notify<T: Serialize>(&self, ty: MonitorTopic, event: T) {
+        let event = serde_json::json!(event);
+        // Add the new event to the ringbuffer
+        match self.buffer.lock().await.get_mut(&ty) {
+            Some(events) => events.push(event.clone()),
+            None => todo!(),
+        }
+
+        // Notify the subscribers
+        match self.subs.lock().await.get_mut(&ty) {
+            Some(subs) => {
+                let mut fulist = FuturesUnordered::new();
+
+                for sub in subs.values() {
+                    let fu = async { (sub.id, sub.notify(event.clone()).await) };
+                    fulist.push(fu)
+                }
+
+                let mut cleanup_list = vec![];
+                while let Some((sub_id, result)) = fulist.next().await {
+                    if let Err(err) = result {
+                        error!("Failed to notify the subscription: {:?} {sub_id} {err}", ty);
+                        cleanup_list.push(sub_id);
+                    }
+                }
+                drop(fulist);
+
+                for sub_id in cleanup_list {
+                    subs.remove(&sub_id);
+                }
+            }
+            None => todo!(),
+        }
+    }
+
+    /// Sends old events in the ringbuffer to the new subscriber.
+    async fn send_old_events(self: &Arc<Self>, ty: MonitorTopic, sub: Subscription) {
+        let ty_cloned = ty.clone();
+        let sub_id = sub.id;
+        let on_complete = move |res: TaskResult<()>| async move {
+            debug!("Send old events: {:?} {:?} {res}", ty_cloned, sub_id);
+        };
+
+        let selfc = self.clone();
+        self.task_group.spawn(
+            async move {
+                match selfc.buffer.lock().await.get_mut(&ty) {
+                    Some(events) => {
+                        let mut fu = FuturesUnordered::new();
+
+                        for event in events.iter().rev() {
+                            fu.push(sub.notify(event.clone()))
+                        }
+
+                        while let Some(result) = fu.next().await {
+                            if result.is_err() {
+                                return;
+                            }
+                        }
+                    }
+                    None => todo!(),
+                }
+            },
+            on_complete,
+        );
+    }
+
+    async fn stop(&self) {
+        self.task_group.cancel().await;
+    }
+}