fix: improve watchdog reliability

watchdog/print-watchdog.sh

@@ -18,6 +18,7 @@ COMMAND_TIMEOUT=8
 FAIL_THRESHOLD=2
 RESTART_COOLDOWN=60
 LOG_FILE="/var/log/cups-watchdog/print.log"
+MAX_LOG_SIZE_KB=256
 
 if [ -f "$CONFIG_FILE" ]; then
     # shellcheck disable=SC1090
@@ -27,9 +28,29 @@ fi
 mkdir -p "$STATE_DIR"
 mkdir -p "$(dirname "$LOG_FILE")" 2>/dev/null || true
 
+acquire_lock() {
+    local lock_dir="$STATE_DIR/print.lock"
+
+    if ! mkdir "$lock_dir" 2>/dev/null; then
+        echo "$(date '+%Y-%m-%d %H:%M:%S') [print-watchdog] another run is active"
+        exit 0
+    fi
+    trap 'rmdir "$lock_dir" 2>/dev/null || true' EXIT
+}
+
+rotate_log() {
+    local max_bytes=$((MAX_LOG_SIZE_KB * 1024))
+
+    if [ -f "$LOG_FILE" ] && [ "$(wc -c < "$LOG_FILE" 2>/dev/null || echo 0)" -gt "$max_bytes" ]; then
+        mv "$LOG_FILE" "$LOG_FILE.1" 2>/dev/null || true
+        : > "$LOG_FILE"
+    fi
+}
+
 log_msg() {
     local msg="$1"
     local line
+    rotate_log
     line="$(date '+%Y-%m-%d %H:%M:%S') [print-watchdog] $msg"
     echo "$line"
     echo "$line" >> "$LOG_FILE" 2>/dev/null || true
@@ -150,9 +171,11 @@ check_print_stack() {
 
 case "${1:-check}" in
     check)
+        acquire_lock
         check_print_stack
         ;;
     restart)
+        acquire_lock
         restart_print_stack
         ;;
     *)