From 4534b331e48ddb436939a6a46ed829673bedd846 Mon Sep 17 00:00:00 2001
From: Thanos Makatos <thanos.makatos@nutanix.com>
Date: Fri, 7 Aug 2026 09:48:47 +0000
Subject: [PATCH] add dedicated D-Bus version method

Signed-off-by: Thanos Makatos <thanos.makatos@nutanix.com>
---
 src/controller.rs | 31 ++++++++++++++++++++-----------
 src/daemon.rs     | 10 ++++++++++
 src/dbus.rs       | 20 ++++++++++++++++++++
 src/main.rs       |  7 ++++++-
 4 files changed, 56 insertions(+), 12 deletions(-)

diff --git a/src/controller.rs b/src/controller.rs
index e6b83a2..59e2557 100644
--- a/src/controller.rs
+++ b/src/controller.rs
@@ -278,6 +278,9 @@ impl Controller {
             DbusRequest::GetSnapshot { reply } => {
                 let _ = reply.send(self.handle_get_snapshot().await);
             }
+            DbusRequest::GetVersion { reply } => {
+                let _ = reply.send(env!("CARGO_PKG_VERSION").to_string());
+            }
             DbusRequest::GetIoThreadVqMapping { vm, device, reply } => {
                 let result = match self.instances.get(&vm) {
                     Some(instance) => instance
@@ -559,8 +562,10 @@ impl Controller {
                 .await;
             tracing::info!(
                 target: "controller",
-                id = %instance.id,
-                ""
+                event = "scale_blocked",
+                reason = "manual_override",
+                vm = %instance.id,
+                action = %action
             );
             return Ok(());
         }
@@ -570,8 +575,10 @@ impl Controller {
                 .await;
             tracing::info!(
                 target: "controller",
-                id = %instance.id,
-                ""
+                event = "scale_blocked",
+                reason = "unmanaged_vm",
+                vm = %instance.id,
+                action = %action
             );
             return Ok(());
         }
@@ -664,10 +671,12 @@ impl Controller {
                     .await;
                 tracing::info!(
                     target: "controller",
-                    id = %instance.id,
-                    %action,
+                    event = "scale_applied",
+                    vm = %instance.id,
+                    action = %action,
                     target,
-                    ""
+                    prev_thread_count = previous_count,
+                    prev_io_count_total = previous_io_count
                 );
             }
             Err(error) => {
@@ -677,11 +686,11 @@ impl Controller {
                     .await;
                 tracing::warn!(
                     target: "controller",
-                    id = %instance.id,
-                    %action,
+                    event = "scale_failed",
+                    vm = %instance.id,
+                    action = %action,
                     target,
-                    error = %error_text,
-                    ""
+                    error = %error_text
                 );
             }
         }
diff --git a/src/daemon.rs b/src/daemon.rs
index d9e1cb0..d72d8d5 100644
--- a/src/daemon.rs
+++ b/src/daemon.rs
@@ -12,6 +12,11 @@ use inotify::{Inotify, WatchMask};
 use thiserror::Error;
 use tokio::time::{MissedTickBehavior, interval};
 
+pub const VERSION: &str = match option_env!("IO_THREAD_CONTROLLER_VERSION") {
+    Some(v) => v,
+    None => "unknown",
+};
+
 use crate::{
     backends::Backend,
     config::Config,
@@ -48,6 +53,11 @@ const INOTIFY_EVENT_BUF_SIZE: usize = 32 * 1024;
 
 /// Run until SIGTERM or SIGINT.
 pub async fn run(cfg: Config, backends: Vec<Box<dyn Backend>>) -> Result<(), DaemonError> {
+    tracing::info!(
+        target: "controller",
+        version = VERSION,
+        "io-thread-controller starting"
+    );
     if cfg.print_status_header {
         tracing::info!(
             target: "status",
diff --git a/src/dbus.rs b/src/dbus.rs
index 34eee3f..fa9cbf2 100644
--- a/src/dbus.rs
+++ b/src/dbus.rs
@@ -12,6 +12,7 @@
 //! Verbs currently exposed:
 //!   * debug-only `SetThreadCount(vm, threads, sticky)`;
 //!   * read-only `GetStats()`;
+//!   * read-only `GetVersion()`;
 //!   * named-IOThread and virtqueue-mapping operations for clients that support
 //!     them.
 
@@ -62,6 +63,11 @@ pub enum DbusRequest {
         /// [`crate::controller::SnapshotPayload`] on success.
         reply: oneshot::Sender<String>,
     },
+    /// Return the controller binary version string.
+    GetVersion {
+        /// Reply channel carrying the version string.
+        reply: oneshot::Sender<String>,
+    },
     /// Read the current virtqueue-to-IOThread mapping.
     GetIoThreadVqMapping {
         /// Instance / vm id to address.
@@ -190,6 +196,20 @@ impl Service {
         await_with_timeout(rx).await
     }
 
+    /// D-Bus wire signature: `GetVersion() -> s`.
+    ///
+    /// Returns the controller binary version string (same source as startup
+    /// logs), exposed separately so high-frequency snapshot payloads stay
+    /// focused on dynamic metrics.
+    async fn get_version(&self) -> zbus::fdo::Result<String> {
+        let (tx, rx) = oneshot::channel();
+        self.tx
+            .send(DbusRequest::GetVersion { reply: tx })
+            .await
+            .map_err(|_| zbus::fdo::Error::Failed("controller channel closed".into()))?;
+        await_with_timeout(rx).await
+    }
+
     async fn get_io_thread_vq_mapping(
         &self,
         vm: String,
diff --git a/src/main.rs b/src/main.rs
index f011b6a..dd0a159 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -12,7 +12,7 @@ use io_thread_controller::{
     backends::BackendClientError,
     backends::registered_backends,
     config::{Config, ConfigError, dump_default_config, load_config, validate_config},
-    daemon::{DaemonError, run},
+    daemon::{DaemonError, VERSION, run},
     util::Path,
 };
 use thiserror::Error;
@@ -37,6 +37,11 @@ enum IoThreadControllerError {
 
 #[derive(Debug, Parser)]
 #[command(
+    // Populated at build time by `build.rs` from the git tree
+    // (short hash, with `-dirty` when the tree had uncommitted
+    // changes).  Falls back to `CARGO_PKG_VERSION` for tarball
+    // builds where `.git` is absent.
+    version = VERSION,
     name = "io-thread-controller",
     about = "Measure VM I/O workers and resize their pools through a selectable scaling engine."
 )]