Add Xvfb monitoring and restart functionality

- Move startup script to scripts/docker-start.sh for better organization
- Add automatic monitoring and restart of Xvfb if it crashes
- Improve error handling and cleanup on container shutdown
- Prevents cache update failures when Xvfb process dies

Dockerfile

@@ -34,12 +34,9 @@ COPY --from=publish /app/publish .
 # Create cache directory for screenshots
 RUN mkdir -p /app/cache && chmod 777 /app/cache
 
-# Create startup script to run Xvfb and then the app
+# Copy startup script
-RUN echo '#!/bin/bash\n\
+COPY scripts/docker-start.sh /app/start.sh
-Xvfb :99 -screen 0 1920x1080x24 > /dev/null 2>&1 &\n\
+RUN chmod +x /app/start.sh
-export DISPLAY=:99\n\
-exec dotnet BomLocalService.dll' > /app/start.sh && \
-    chmod +x /app/start.sh
 
 # OCI labels for GitHub Container Registry metadata
 LABEL org.opencontainers.image.source="https://github.com/alexhopeoconnor/bom-local-service"

scripts/docker-start.sh

@@ -0,0 +1,50 @@
+#!/bin/bash
+set -e
+
+# Function to start Xvfb
+start_xvfb() {
+    if ! pgrep -f "Xvfb :99" > /dev/null; then
+        echo "Starting Xvfb on display :99..."
+        Xvfb :99 -screen 0 1920x1080x24 -ac +extension GLX +render -noreset > /dev/null 2>&1 &
+        sleep 1
+        if ! pgrep -f "Xvfb :99" > /dev/null; then
+            echo "ERROR: Xvfb failed to start" >&2
+            return 1
+        fi
+        echo "Xvfb started successfully"
+    fi
+    return 0
+}
+
+# Function to monitor and restart Xvfb if it dies (runs as background process)
+monitor_xvfb() {
+    # Monitor while PID 1 (dotnet after exec) is still running
+    while kill -0 1 2>/dev/null; do
+        sleep 5
+        if ! pgrep -f "Xvfb :99" > /dev/null; then
+            echo "WARNING: Xvfb process not found, restarting..." >&2
+            start_xvfb || true
+        fi
+    done
+}
+
+# Cleanup function
+cleanup() {
+    echo "Shutting down Xvfb..."
+    pkill -f "Xvfb :99" || true
+}
+
+# Set up signal handlers for cleanup
+trap cleanup SIGTERM SIGINT EXIT
+
+# Start Xvfb
+start_xvfb || exit 1
+
+# Export DISPLAY
+export DISPLAY=:99
+
+# Start monitoring in background (will check if PID 1 is still running)
+monitor_xvfb &
+
+# Start the .NET application (replaces shell as PID 1)
+exec dotnet BomLocalService.dll