snarkos_node_tcp/protocols/
disconnect.rs

1// Copyright (c) 2019-2026 Provable Inc.
2// This file is part of the snarkOS library.
3
4// Licensed under the Apache License, Version 2.0 (the "License");
5// you may not use this file except in compliance with the License.
6// You may obtain a copy of the License at:
7
8// http://www.apache.org/licenses/LICENSE-2.0
9
10// Unless required by applicable law or agreed to in writing, software
11// distributed under the License is distributed on an "AS IS" BASIS,
12// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13// See the License for the specific language governing permissions and
14// limitations under the License.
15
16use std::{net::SocketAddr, time::Duration};
17
18use tokio::{
19    sync::{mpsc, oneshot},
20    task::JoinHandle,
21    time::timeout,
22};
23use tracing::*;
24
25#[cfg(doc)]
26use crate::{Connection, protocols::Writing};
27use crate::{
28    P2P,
29    connections::{DisconnectOrigin, create_connection_span},
30    protocols::ProtocolHandler,
31};
32
33/// Can be used to automatically perform some extra actions when the node disconnects from its
34/// peer, which is especially practical if the disconnect is triggered automatically, e.g. due
35/// to the peer exceeding the allowed number of failures or severing its connection with the node
36/// on its own.
37#[async_trait::async_trait]
38pub trait Disconnect: P2P
39where
40    Self: Clone + Send + Sync + 'static,
41{
42    /// The maximum time allowed for the on_disconnect hook to execute.
43    /// If the hook exceeds this time, it will be aborted to ensure the node cleans up
44    /// resources promptly.
45    const TIMEOUT: Duration = Duration::from_secs(3);
46
47    /// Attaches the behavior specified in [`Disconnect::handle_disconnect`] to every occurrence of the
48    /// node disconnecting from a peer.
49    async fn enable_disconnect(&self) {
50        let (from_node_sender, mut from_node_receiver) = mpsc::channel::<(
51            (SocketAddr, DisconnectOrigin),
52            oneshot::Sender<(JoinHandle<()>, oneshot::Receiver<()>)>,
53        )>(self.tcp().config().max_connections as usize);
54
55        // use a channel to know when the disconnect task is ready
56        let (tx, rx) = oneshot::channel::<()>();
57
58        // spawn a background task dedicated to handling disconnect events
59        let self_clone = self.clone();
60        let disconnect_task = tokio::spawn(async move {
61            trace!(parent: self_clone.tcp().span(), "spawned the Disconnect handler task");
62            tx.send(()).unwrap(); // safe; the channel was just opened
63
64            while let Some(((peer_addr, origin), notifier)) = from_node_receiver.recv().await {
65                let self_clone2 = self_clone.clone();
66                // create a channel for waiting on completion
67                let (done_tx, done_rx) = oneshot::channel();
68                let handle = tokio::spawn(async move {
69                    // perform the specified extra actions
70                    if timeout(Self::TIMEOUT, self_clone2.handle_disconnect(peer_addr, origin)).await.is_err() {
71                        let conn_span = create_connection_span(peer_addr, self_clone2.tcp().span());
72                        warn!(parent: conn_span, "Disconnect logic timed out");
73                    }
74                    // notify the node that the extra actions have concluded
75                    // and that the related connection can be dropped
76                    let _ = done_tx.send(());
77                });
78                // provide the node with a handle to the scheduled task,
79                // and a receiver that will notify it of its completion
80                let _ = notifier.send((handle, done_rx)); // can't really fail
81            }
82        });
83        let _ = rx.await;
84        self.tcp().tasks.lock().push(disconnect_task);
85
86        // register the Disconnect handler with the Tcp
87        let hdl = Box::new(ProtocolHandler(from_node_sender));
88        assert!(
89            self.tcp().protocols.disconnect.set(hdl).is_ok(),
90            "the Disconnect protocol was enabled more than once!"
91        );
92    }
93
94    /// Any extra actions to be executed during a disconnect; in order to still be able to
95    /// communicate with the peer in the usual manner (i.e. via [`Writing`]), only its [`SocketAddr`]
96    /// (as opposed to the related [`Connection`] object) is provided as an argument.
97    async fn handle_disconnect(&self, peer_addr: SocketAddr, origin: DisconnectOrigin);
98}
snarkos_node_tcp/protocols/disconnect.rs

snarkos_node_tcp/protocols/
disconnect.rs
