refactor: consolidate metric collection into single SSH calls and add support for SSH key authentication

bin/monitor_metrics.sh

@@ -2,15 +2,24 @@
 
 # Monitor and restart metrics collector if it's not running
 # This script checks if collect_metrics.php is running and restarts it if needed
+# Uses flock to prevent multiple instances (#42)
 
 SCRIPT_PATH="/var/www/html/bin/collect_metrics.php"
 LOG_FILE="/var/log/metrics_monitor.log"
 PID_FILE="/var/run/collect_metrics.pid"
+LOCK_FILE="/var/run/collect_metrics.lock"
 
 log_message() {
     echo "[$(date '+%Y-%m-%d %H:%M:%S')] $1" >> "$LOG_FILE"
 }
 
+# Use flock to prevent multiple monitor instances
+exec 200>"$LOCK_FILE"
+if ! flock -n 200; then
+    log_message "Another monitor instance is running, exiting"
+    exit 0
+fi
+
 # Check if the process is running
 is_running() {
     if [ -f "$PID_FILE" ]; then
@@ -22,6 +31,12 @@ is_running() {
             fi
         fi
     fi
+    # Also check if any collect_metrics.php is running (catches orphan processes)
+    if pgrep -f "collect_metrics.php" > /dev/null 2>&1; then
+        # Update PID file with actual PID
+        pgrep -f "collect_metrics.php" | head -1 > "$PID_FILE"
+        return 0
+    fi
     return 1
 }