Allow for per-test dbus sessions

src/controller.rs

@@ -312,6 +312,7 @@ impl Controller {
                         "thread_count": status.thread_count,
                         "manual_scaling_sticky": status.manual_scaling_sticky,
                         "scaling_allowed": status.scaling_allowed,
+                        "alive": status.alive,
                         "vcpu_count": status.vcpu_count,
                         "per_thread_util": status.per_thread_util,
                         // FIXME omit if status.perf.is_none()?

src/daemon.rs

@@ -79,7 +79,8 @@ pub async fn run(cfg: Config, backends: Vec<Box<dyn Backend>>) -> Result<(), Dae
     tracing::info!(target: "controller", added, "initial discovery");
 
     let (dbus_tx, mut dbus_rx) = tokio::sync::mpsc::channel(1);
-    let _dbus_connection = dbus::serve(dbus::Service::new(dbus_tx)).await?;
+    let service = dbus::Service::new(dbus_tx);
+    let _dbus_connection = dbus::serve(service).await?;
     let mut inotify_events = setup_inotify(&backends)?;
     let mut poll = interval(Duration::from_secs_f64(cfg.scale_poll_secs));
     poll.set_missed_tick_behavior(MissedTickBehavior::Skip);

src/dbus.rs

@@ -289,8 +289,22 @@ impl Service {
 
 /// Spin the D-Bus service on the well-known name / object path
 /// backed by `service` and drive replies from the controller mpsc.
+///
+/// Component tests set `IO_THREAD_CONTROLLER_DBUS_ADDRESS` to use their
+/// private bus; production leaves it unset and uses the system bus.
 pub async fn serve(service: Service) -> Result<zbus::Connection, zbus::Error> {
-    let conn = zbus::connection::Builder::system()?
+    let builder = match std::env::var("IO_THREAD_CONTROLLER_DBUS_ADDRESS") {
+        Ok(address) => zbus::connection::Builder::address(address.as_str())?,
+        Err(_) => zbus::connection::Builder::system()?,
+    };
+    serve_with(builder, service).await
+}
+
+async fn serve_with(
+    builder: zbus::connection::Builder<'_>,
+    service: Service,
+) -> Result<zbus::Connection, zbus::Error> {
+    let conn = builder
         .name(DBUS_BUS_NAME)?
         .serve_at(DBUS_OBJECT_PATH, service)?
         .build()