Fix agent hang by reverting service discovery to systemctl

The D-Bus ListUnits call in discover_services_internal() was causing
the agent to hang on startup.

**Root cause:**
- D-Bus ListUnits call with complex tuple destructuring hung indefinitely
- Agent never completed first collection cycle
- No collector output in logs

**Fix:**
- Revert discover_services_internal() to use systemctl list-units/list-unit-files
- Keep D-Bus-based property queries (WorkingDirectory, MemoryCurrent, ExecStart)
- Hybrid approach: systemctl for discovery, D-Bus for individual queries

**External commands still used:**
- systemctl list-units, list-unit-files (service discovery)
- smartctl (SMART data)
- sudo du (directory sizes)
- nginx -T (config fallback)

Version bump: 0.1.198 → 0.1.199

Cargo.lock

@@ -493,7 +493,7 @@ checksum = "a1d728cc89cf3aee9ff92b05e62b19ee65a02b5702cff7d5a377e32c6ae29d8d"
 
 [[package]]
 name = "cm-dashboard"
-version = "0.1.198"
+version = "0.1.199"
 dependencies = [
  "anyhow",
  "chrono",
@@ -515,7 +515,7 @@ dependencies = [
 
 [[package]]
 name = "cm-dashboard-agent"
-version = "0.1.198"
+version = "0.1.199"
 dependencies = [
  "anyhow",
  "async-trait",
@@ -545,7 +545,7 @@ dependencies = [
 
 [[package]]
 name = "cm-dashboard-shared"
-version = "0.1.198"
+version = "0.1.199"
 dependencies = [
  "chrono",
  "serde",

agent/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "cm-dashboard-agent"
-version = "0.1.198"
+version = "0.1.199"
 edition = "2021"
 
 [dependencies]

agent/src/collectors/systemd.rs

@@ -263,45 +263,71 @@ impl SystemdCollector {
         state.nginx_site_metrics.clone()
     }
 
-    /// Auto-discover interesting services to monitor using D-Bus
+    /// Auto-discover interesting services to monitor using systemctl
     async fn discover_services_internal(&self) -> Result<(Vec<String>, std::collections::HashMap<String, ServiceStatusInfo>)> {
-        // Connect to system D-Bus
-        let connection = Connection::system().await?;
+        // First: Get all service unit files (with 3 second timeout)
+        let unit_files_output = Command::new("timeout")
+            .args(&["3", "systemctl", "list-unit-files", "--type=service", "--no-pager", "--plain"])
+            .output()?;
 
-        // Get systemd manager proxy
-        let proxy = zbus::Proxy::new(
-            &connection,
-            "org.freedesktop.systemd1",
-            "/org/freedesktop/systemd1",
-            "org.freedesktop.systemd1.Manager",
-        ).await?;
+        if !unit_files_output.status.success() {
+            return Err(anyhow::anyhow!("systemctl list-unit-files command failed"));
+        }
 
-        // List all units via D-Bus
-        let units: Vec<(String, String, String, String, String, String, zbus::zvariant::OwnedObjectPath, u32, String, zbus::zvariant::OwnedObjectPath)> =
-            proxy.call("ListUnits", &()).await?;
+        // Second: Get runtime status of all units (with 3 second timeout)
+        let units_status_output = Command::new("timeout")
+            .args(&["3", "systemctl", "list-units", "--type=service", "--all", "--no-pager", "--plain"])
+            .output()?;
 
+        if !units_status_output.status.success() {
+            return Err(anyhow::anyhow!("systemctl list-units command failed"));
+        }
+
+        let unit_files_str = String::from_utf8(unit_files_output.stdout)?;
+        let units_status_str = String::from_utf8(units_status_output.stdout)?;
+        let mut services = Vec::new();
+
+        let excluded_services = &self.config.excluded_services;
+        let service_name_filters = &self.config.service_name_filters;
+
+        // Parse all service unit files
         let mut all_service_names = std::collections::HashSet::new();
-        let mut service_status_cache = std::collections::HashMap::new();
-
-        // Parse D-Bus response for services only
-        for unit in units {
-            let (unit_name, _description, load_state, active_state, sub_state, _followed, _unit_path, _job_id, _job_type, _job_path) = unit;
-
-            if unit_name.ends_with(".service") {
-                let service_name = unit_name.trim_end_matches(".service");
+        for line in unit_files_str.lines() {
+            let fields: Vec<&str> = line.split_whitespace().collect();
+            if fields.len() >= 2 && fields[0].ends_with(".service") {
+                let service_name = fields[0].trim_end_matches(".service");
                 all_service_names.insert(service_name.to_string());
+            }
+        }
 
-                service_status_cache.insert(service_name.to_string(), ServiceStatusInfo {
-                    load_state: load_state.clone(),
-                    active_state: active_state.clone(),
-                    sub_state: sub_state.clone(),
+        // Parse runtime status for all units
+        let mut status_cache = std::collections::HashMap::new();
+        for line in units_status_str.lines() {
+            let fields: Vec<&str> = line.split_whitespace().collect();
+            if fields.len() >= 4 && fields[0].ends_with(".service") {
+                let service_name = fields[0].trim_end_matches(".service");
+                let load_state = fields.get(1).unwrap_or(&"unknown").to_string();
+                let active_state = fields.get(2).unwrap_or(&"unknown").to_string();
+                let sub_state = fields.get(3).unwrap_or(&"unknown").to_string();
+
+                status_cache.insert(service_name.to_string(), ServiceStatusInfo {
+                    load_state,
+                    active_state,
+                    sub_state,
                 });
             }
         }
 
-        let mut services = Vec::new();
-        let excluded_services = &self.config.excluded_services;
-        let service_name_filters = &self.config.service_name_filters;
+        // For services found in unit files but not in runtime status, set default inactive status
+        for service_name in &all_service_names {
+            if !status_cache.contains_key(service_name) {
+                status_cache.insert(service_name.to_string(), ServiceStatusInfo {
+                    load_state: "not-loaded".to_string(),
+                    active_state: "inactive".to_string(),
+                    sub_state: "dead".to_string(),
+                });
+            }
+        }
 
         // Process all discovered services and apply filters
         for service_name in &all_service_names {
@@ -327,7 +353,7 @@ impl SystemdCollector {
             }
         }
 
-        Ok((services, service_status_cache))
+        Ok((services, status_cache))
     }
 
     /// Get service status from D-Bus cache

dashboard/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "cm-dashboard"
-version = "0.1.198"
+version = "0.1.199"
 edition = "2021"
 
 [dependencies]

shared/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "cm-dashboard-shared"
-version = "0.1.198"
+version = "0.1.199"
 edition = "2021"
 
 [dependencies]