Reduce CPU usage with conditional rendering

Implement event-driven rendering to dramatically reduce CPU usage.
Only render when something actually changes instead of constantly
rendering at 20 FPS.

Changes:
- Increase poll timeout from 50ms to 200ms (5 FPS)
- Add needs_render flag to track when rendering is required
- Trigger rendering only on: user input, new metrics, heartbeat
  checks, or terminal resize events
- Reset render flag after each render cycle

Based on cm-player optimization approach.

Cargo.lock

@@ -279,7 +279,7 @@ checksum = "a1d728cc89cf3aee9ff92b05e62b19ee65a02b5702cff7d5a377e32c6ae29d8d"
 
 [[package]]
 name = "cm-dashboard"
-version = "0.1.264"
+version = "0.1.265"
 dependencies = [
  "anyhow",
  "chrono",
@@ -301,7 +301,7 @@ dependencies = [
 
 [[package]]
 name = "cm-dashboard-agent"
-version = "0.1.264"
+version = "0.1.265"
 dependencies = [
  "anyhow",
  "async-trait",
@@ -325,7 +325,7 @@ dependencies = [
 
 [[package]]
 name = "cm-dashboard-shared"
-version = "0.1.264"
+version = "0.1.265"
 dependencies = [
  "chrono",
  "serde",

agent/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "cm-dashboard-agent"
-version = "0.1.265"
+version = "0.1.266"
 edition = "2021"
 
 [dependencies]

dashboard/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "cm-dashboard"
-version = "0.1.265"
+version = "0.1.266"
 edition = "2021"
 
 [dependencies]

dashboard/src/app.rs

@@ -138,11 +138,12 @@ impl Dashboard {
         let metrics_check_interval = Duration::from_millis(100); // Check for metrics every 100ms
         let mut last_heartbeat_check = Instant::now();
         let heartbeat_check_interval = Duration::from_secs(1); // Check for host connectivity every 1 second
+        let mut needs_render = true; // Track if we need to render
 
         loop {
             // Handle terminal events (keyboard and mouse input) only if not headless
             if !self.headless {
-                match event::poll(Duration::from_millis(50)) {
+                match event::poll(Duration::from_millis(200)) {
                     Ok(true) => {
                         match event::read() {
                             Ok(event) => {
@@ -152,6 +153,7 @@ impl Dashboard {
                                             // Handle keyboard input
                                             match tui_app.handle_input(event) {
                                                 Ok(_) => {
+                                                    needs_render = true;
                                                     // Check if we should quit
                                                     if tui_app.should_quit() {
                                                         info!("Quit requested, exiting dashboard");
@@ -168,10 +170,11 @@ impl Dashboard {
                                             if let Err(e) = self.handle_mouse_event(mouse_event) {
                                                 error!("Error handling mouse event: {}", e);
                                             }
+                                            needs_render = true;
                                         }
                                         Event::Resize(_width, _height) => {
-                                            // Terminal was resized - just continue and re-render
-                                            // The next render will automatically use the new size
+                                            // Terminal was resized - mark for re-render
+                                            needs_render = true;
                                         }
                                         _ => {}
                                     }
@@ -189,38 +192,6 @@ impl Dashboard {
                         break;
                     }
                 }
-
-                // Render UI immediately after handling input for responsive feedback
-                if let Some(ref mut terminal) = self.terminal {
-                    if let Some(ref mut tui_app) = self.tui_app {
-                        // Clear and autoresize terminal to handle any resize events
-                        if let Err(e) = terminal.autoresize() {
-                            warn!("Error autoresizing terminal: {}", e);
-                        }
-
-                        // Check minimum terminal size to prevent panics
-                        let size = terminal.size().unwrap_or_default();
-                        if size.width < 90 || size.height < 15 {
-                            // Terminal too small, show error message
-                            let msg_text = format!("Terminal too small\n\nMinimum: 90x15\nCurrent: {}x{}", size.width, size.height);
-                            let _ = terminal.draw(|frame| {
-                                use ratatui::widgets::{Paragraph, Block, Borders};
-                                use ratatui::layout::Alignment;
-                                let msg = Paragraph::new(msg_text.clone())
-                                    .alignment(Alignment::Center)
-                                    .block(Block::default().borders(Borders::ALL));
-                                frame.render_widget(msg, frame.size());
-                            });
-                        } else if let Err(e) = terminal.draw(|frame| {
-                            let (title_area, system_area, services_area) = tui_app.render(frame, &self.metric_store);
-                            self.title_area = title_area;
-                            self.system_area = system_area;
-                            self.services_area = services_area;
-                        }) {
-                            error!("Error rendering TUI after input: {}", e);
-                        }
-                    }
-                }
             }
 
             // Check for new metrics
@@ -259,8 +230,10 @@ impl Dashboard {
                     if let Some(ref mut tui_app) = self.tui_app {
                         tui_app.update_metrics(&mut self.metric_store);
                     }
+
+                    needs_render = true; // New metrics received, need to render
                 }
-                
+
                 // Also check for command output messages
                 if let Ok(Some(cmd_output)) = self.zmq_consumer.receive_command_output().await {
                     debug!(
@@ -271,26 +244,27 @@ impl Dashboard {
 
                     // Command output (terminal popup removed - output not displayed)
                 }
-                
+
                 last_metrics_check = Instant::now();
             }
 
             // Check for host connectivity changes (heartbeat timeouts) periodically
             if last_heartbeat_check.elapsed() >= heartbeat_check_interval {
                 let timeout = Duration::from_secs(self.config.zmq.heartbeat_timeout_seconds);
-                
+
                 // Clean up metrics for offline hosts
                 self.metric_store.cleanup_offline_hosts(timeout);
-                
+
                 if let Some(ref mut tui_app) = self.tui_app {
                     let connected_hosts = self.metric_store.get_connected_hosts(timeout);
                     tui_app.update_hosts(connected_hosts);
                 }
                 last_heartbeat_check = Instant::now();
+                needs_render = true; // Heartbeat check happened, may have changed hosts
             }
 
-            // Render TUI (only if not headless)
-            if !self.headless {
+            // Render TUI only when needed (not headless and something changed)
+            if !self.headless && needs_render {
                 if let Some(ref mut terminal) = self.terminal {
                     if let Some(ref mut tui_app) = self.tui_app {
                         // Clear and autoresize terminal to handle any resize events
@@ -322,10 +296,8 @@ impl Dashboard {
                         }
                     }
                 }
+                needs_render = false; // Reset flag after rendering
             }
-
-            // Small sleep to prevent excessive CPU usage
-            tokio::time::sleep(Duration::from_millis(10)).await;
         }
 
         info!("Dashboard main loop ended");

shared/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "cm-dashboard-shared"
-version = "0.1.265"
+version = "0.1.266"
 edition = "2021"
 
 [dependencies]