feat(console): add support for Unix domain sockets (#388)

Add support for console connections that use Unix domain sockets rather
than TCP.

Closes #296.

Co-authored-by: Eliza Weisman <eliza@buoyant.io>

console-subscriber/Cargo.toml

@@ -33,7 +33,7 @@ env-filter = ["tracing-subscriber/env-filter"]
 
 crossbeam-utils = "0.8.7"
 tokio = { version = "^1.21", features = ["sync", "time", "macros", "tracing"] }
-tokio-stream = "0.1"
+tokio-stream = { version = "0.1", features = ["net"] }
 thread_local = "1.1.3"
 console-api = { version = "0.4.0", path = "../console-api", features = ["transport"] }
 tonic = { version = "0.8", features = ["transport"] }

console-subscriber/examples/uds.rs

@@ -0,0 +1,40 @@
+//! Demonstrates serving the console API over a [Unix domain socket] (UDS)
+//! connection, rather than over TCP.
+//!
+//! Note that this example only works on Unix operating systems that
+//! support UDS, such as Linux, BSDs, and macOS.
+//!
+//! [Unix domain socket]: https://en.wikipedia.org/wiki/Unix_domain_socket
+
+#[cfg(unix)]
+use {
+    std::time::Duration,
+    tokio::{fs, task, time},
+    tracing::info,
+};
+
+#[cfg(unix)]
+#[tokio::main]
+async fn main() -> Result<(), Box<dyn std::error::Error + Send + Sync>> {
+    let cwd = fs::canonicalize(".").await?;
+    let addr = cwd.join("console-server");
+    console_subscriber::ConsoleLayer::builder()
+        .server_addr(&*addr)
+        .init();
+    info!(
+        "listening for console connections at file://localhost{}",
+        addr.display()
+    );
+    task::Builder::default()
+        .name("sleepy")
+        .spawn(async move { time::sleep(Duration::from_secs(90)).await })
+        .unwrap()
+        .await?;
+
+    Ok(())
+}
+
+#[cfg(not(unix))]
+fn main() {
+    panic!("only supported on Unix platforms")
+}

console-subscriber/src/builder.rs

@@ -1,6 +1,8 @@
 use super::{ConsoleLayer, Server};
+#[cfg(unix)]
+use std::path::Path;
 use std::{
-    net::{SocketAddr, ToSocketAddrs},
+    net::{IpAddr, SocketAddr, SocketAddrV4, SocketAddrV6, ToSocketAddrs},
     path::PathBuf,
     thread,
     time::Duration,
@@ -32,7 +34,7 @@ pub struct Builder {
     pub(crate) retention: Duration,
 
     /// The address on which to serve the RPC server.
-    pub(super) server_addr: SocketAddr,
+    pub(super) server_addr: ServerAddr,
 
     /// If and where to save a recording of the events.
     pub(super) recording_path: Option<PathBuf>,
@@ -58,7 +60,7 @@ impl Default for Builder {
             publish_interval: ConsoleLayer::DEFAULT_PUBLISH_INTERVAL,
             retention: ConsoleLayer::DEFAULT_RETENTION,
             poll_duration_max: ConsoleLayer::DEFAULT_POLL_DURATION_MAX,
-            server_addr: SocketAddr::new(Server::DEFAULT_IP, Server::DEFAULT_PORT),
+            server_addr: ServerAddr::Tcp(SocketAddr::new(Server::DEFAULT_IP, Server::DEFAULT_PORT)),
             recording_path: None,
             filter_env_var: "RUST_LOG".to_string(),
             self_trace: false,
@@ -137,8 +139,38 @@ impl Builder {
     /// before falling back on constructing a socket address from those
     /// defaults.
     ///
+    /// The socket address can be either a TCP socket address or a
+    /// [Unix domain socket] (UDS) address. Unix domain sockets are only
+    /// supported on Unix-compatible operating systems, such as Linux, BSDs,
+    /// and macOS.
+    ///
+    /// Each call to this method will overwrite the previously set value.
+    ///
+    /// # Examples
+    ///
+    /// Connect to the TCP address `localhost:1234`:
+    ///
+    /// ```
+    /// # use console_subscriber::Builder;
+    /// use std::net::Ipv4Addr;
+    /// let builder = Builder::default().server_addr((Ipv4Addr::LOCALHOST, 1234));
+    /// ```
+    ///
+    /// Connect to the UDS address `/tmp/tokio-console`:
+    ///
+    /// ```
+    /// # use console_subscriber::Builder;
+    /// # #[cfg(unix)]
+    /// use std::path::Path;
+    ///
+    /// // Unix domain sockets are only available on Unix-compatible operating systems.
+    /// #[cfg(unix)]
+    /// let builder = Builder::default().server_addr(Path::new("/tmp/tokio-console"));
+    /// ```
+    ///
     /// [environment variable]: `Builder::with_default_env`
-    pub fn server_addr(self, server_addr: impl Into<SocketAddr>) -> Self {
+    /// [Unix domain socket]: https://en.wikipedia.org/wiki/Unix_domain_socket
+    pub fn server_addr(self, server_addr: impl Into<ServerAddr>) -> Self {
         Self {
             server_addr: server_addr.into(),
             ..self
@@ -231,11 +263,14 @@ impl Builder {
         }
 
         if let Ok(bind) = std::env::var("TOKIO_CONSOLE_BIND") {
-            self.server_addr = bind
-                .to_socket_addrs()
-                .expect("TOKIO_CONSOLE_BIND must be formatted as HOST:PORT, such as localhost:4321")
-                .next()
-                .expect("tokio console could not resolve TOKIO_CONSOLE_BIND");
+            self.server_addr = ServerAddr::Tcp(
+                bind.to_socket_addrs()
+                    .expect(
+                        "TOKIO_CONSOLE_BIND must be formatted as HOST:PORT, such as localhost:4321",
+                    )
+                    .next()
+                    .expect("tokio console could not resolve TOKIO_CONSOLE_BIND"),
+            );
         }
 
         if let Some(interval) = duration_from_env("TOKIO_CONSOLE_PUBLISH_INTERVAL") {
@@ -456,6 +491,66 @@ impl Builder {
     }
 }
 
+/// Specifies the address on which a [`Server`] should listen.
+///
+/// This type is passed as an argument to the [`Builder::server_addr`]
+/// method, and may be either a TCP socket address, or a [Unix domain socket]
+/// (UDS) address. Unix domain sockets are only supported on Unix-compatible
+/// operating systems, such as Linux, BSDs, and macOS.
+///
+/// [`Server`]: crate::Server
+/// [Unix domain socket]: https://en.wikipedia.org/wiki/Unix_domain_socket
+#[derive(Clone, Debug)]
+#[non_exhaustive]
+pub enum ServerAddr {
+    /// A TCP address.
+    Tcp(SocketAddr),
+    /// A Unix socket address.
+    #[cfg(unix)]
+    Unix(PathBuf),
+}
+
+impl From<SocketAddr> for ServerAddr {
+    fn from(addr: SocketAddr) -> ServerAddr {
+        ServerAddr::Tcp(addr)
+    }
+}
+
+impl From<SocketAddrV4> for ServerAddr {
+    fn from(addr: SocketAddrV4) -> ServerAddr {
+        ServerAddr::Tcp(addr.into())
+    }
+}
+
+impl From<SocketAddrV6> for ServerAddr {
+    fn from(addr: SocketAddrV6) -> ServerAddr {
+        ServerAddr::Tcp(addr.into())
+    }
+}
+
+impl<I> From<(I, u16)> for ServerAddr
+where
+    I: Into<IpAddr>,
+{
+    fn from(pieces: (I, u16)) -> ServerAddr {
+        ServerAddr::Tcp(pieces.into())
+    }
+}
+
+#[cfg(unix)]
+impl From<PathBuf> for ServerAddr {
+    fn from(path: PathBuf) -> ServerAddr {
+        ServerAddr::Unix(path)
+    }
+}
+
+#[cfg(unix)]
+impl<'a> From<&'a Path> for ServerAddr {
+    fn from(path: &'a Path) -> ServerAddr {
+        ServerAddr::Unix(path.to_path_buf())
+    }
+}
+
 /// Initializes the console [tracing `Subscriber`][sub] and starts the console
 /// subscriber [`Server`] on its own background thread.
 ///

console-subscriber/src/lib.rs

@@ -5,15 +5,19 @@ use serde::Serialize;
 use std::{
     cell::RefCell,
     fmt,
-    net::{IpAddr, Ipv4Addr, SocketAddr},
+    net::{IpAddr, Ipv4Addr},
     sync::{
         atomic::{AtomicUsize, Ordering},
         Arc,
     },
     time::{Duration, Instant},
 };
 use thread_local::ThreadLocal;
+#[cfg(unix)]
+use tokio::net::UnixListener;
 use tokio::sync::{mpsc, oneshot};
+#[cfg(unix)]
+use tokio_stream::wrappers::UnixListenerStream;
 use tracing_core::{
     span::{self, Id},
     subscriber::{self, Subscriber},
@@ -36,7 +40,7 @@ pub(crate) mod sync;
 mod visitors;
 
 use aggregator::Aggregator;
-pub use builder::Builder;
+pub use builder::{Builder, ServerAddr};
 use callsites::Callsites;
 use record::Recorder;
 use stack::SpanStack;
@@ -134,7 +138,7 @@ pub struct ConsoleLayer {
 /// [cli]: https://crates.io/crates/tokio-console
 pub struct Server {
     subscribe: mpsc::Sender<Command>,
-    addr: SocketAddr,
+    addr: ServerAddr,
     aggregator: Option<Aggregator>,
     client_buffer: usize,
 }
@@ -945,13 +949,22 @@ impl Server {
             .take()
             .expect("cannot start server multiple times");
         let aggregate = spawn_named(aggregate.run(), "console::aggregate");
-        let addr = self.addr;
-        let serve = builder
-            .add_service(proto::instrument::instrument_server::InstrumentServer::new(
-                self,
-            ))
-            .serve(addr);
-        let res = spawn_named(serve, "console::serve").await;
+        let addr = self.addr.clone();
+        let router = builder.add_service(
+            proto::instrument::instrument_server::InstrumentServer::new(self),
+        );
+        let res = match addr {
+            ServerAddr::Tcp(addr) => {
+                let serve = router.serve(addr);
+                spawn_named(serve, "console::serve").await
+            }
+            #[cfg(unix)]
+            ServerAddr::Unix(path) => {
+                let incoming = UnixListener::bind(path)?;
+                let serve = router.serve_with_incoming(UnixListenerStream::new(incoming));
+                spawn_named(serve, "console::serve").await
+            }
+        };
         aggregate.abort();
         res?.map_err(Into::into)
     }

tokio-console/Cargo.toml

@@ -34,6 +34,7 @@ tokio = { version = "1", features = ["full", "rt-multi-thread"] }
 tonic = { version = "0.8", features = ["transport"] }
 futures = "0.3"
 tui = { version = "0.16.0", default-features = false, features = ["crossterm"] }
+tower = "0.4.12"
 tracing = "0.1"
 tracing-subscriber = { version = "0.3.0", features = ["env-filter"] }
 tracing-journald = { version = "0.2", optional = true }

tokio-console/args.example

@@ -7,6 +7,9 @@ ARGS:
 
             This may be an IP address and port, or a DNS name.
 
+            On Unix platforms, this may also be a URI with the `file` scheme that specifies the path
+            to a Unix domain socket, as in `file://localhost/path/to/socket`.
+
             [default: http://127.0.0.1:6669]
 
 OPTIONS:

tokio-console/src/config.rs

@@ -26,6 +26,10 @@ pub struct Config {
     ///
     /// This may be an IP address and port, or a DNS name.
     ///
+    /// On Unix platforms, this may also be a URI with the `file` scheme that
+    /// specifies the path to a Unix domain socket, as in
+    /// `file://localhost/path/to/socket`.
+    ///
     /// [default: http://127.0.0.1:6669]
     #[clap(value_hint = ValueHint::Url)]
     pub(crate) target_addr: Option<Uri>,

tokio-console/src/conn.rs

@@ -5,7 +5,12 @@ use console_api::instrument::{
 use console_api::tasks::TaskDetails;
 use futures::stream::StreamExt;
 use std::{error::Error, pin::Pin, time::Duration};
-use tonic::{transport::Channel, transport::Uri, Streaming};
+#[cfg(unix)]
+use tokio::net::UnixStream;
+use tonic::{
+    transport::{Channel, Endpoint, Uri},
+    Streaming,
+};
 
 #[derive(Debug)]
 pub struct Connection {
@@ -78,7 +83,31 @@ impl Connection {
                 tokio::time::sleep(backoff).await;
             }
             let try_connect = async {
-                let mut client = InstrumentClient::connect(self.target.clone()).await?;
+                let channel = match self.target.scheme_str() {
+                    #[cfg(unix)]
+                    Some("file") => {
+                        // Dummy endpoint is ignored by the connector.
+                        let endpoint = Endpoint::from_static("http://localhost");
+                        if !matches!(self.target.host(), None | Some("localhost")) {
+                            return Err("cannot connect to non-localhost unix domain socket".into());
+                        }
+                        let path = self.target.path().to_owned();
+                        endpoint
+                            .connect_with_connector(tower::service_fn(move |_| {
+                                UnixStream::connect(path.clone())
+                            }))
+                            .await?
+                    }
+                    #[cfg(not(unix))]
+                    Some("file") => {
+                        return Err("unix domain sockets are not supported on this platform".into());
+                    }
+                    _ => {
+                        let endpoint = Endpoint::try_from(self.target.clone())?;
+                        endpoint.connect().await?
+                    }
+                };
+                let mut client = InstrumentClient::new(channel);
                 let request = tonic::Request::new(InstrumentRequest {});
                 let stream = Box::new(client.watch_updates(request).await?.into_inner());
                 Ok::<State, Box<dyn Error + Send + Sync>>(State::Connected { client, stream })