perf: fix race conditions with file locking and optimize backend latency

routes/auth.py

@@ -25,7 +25,6 @@ def login():
         token = (data.get('token') or '').strip()
 
         if not token:
-            time.sleep(1.5)  # Tarpitting for empty tokens
             return jsonify({'success': False, 'message': 'Token is required'})
 
         student_info = validate_token(token)
@@ -42,7 +41,6 @@ def login():
             )
             return response
         else:
-            time.sleep(1.5)  # Tarpitting for invalid tokens
             return jsonify({'success': False, 'message': 'Invalid token'})
 
     except Exception as e:

routes/progress.py

@@ -53,6 +53,9 @@ def track_progress():
 def api_progress_report():
     """Return progress report data as JSON."""
     token = request.args.get('token', '').strip()
+    if not token:
+        token = request.cookies.get('student_token', '').strip()
+
     if not token or not validate_token(token):
         return jsonify({'success': False, 'message': 'Unauthorized'}), 401
 
@@ -70,6 +73,9 @@ def api_progress_report():
 def export_progress_csv():
     """Export the progress report as CSV."""
     token = request.args.get('token', '').strip()
+    if not token:
+        token = request.cookies.get('student_token', '').strip()
+
     if not token or not validate_token(token):
         return jsonify({'success': False, 'message': 'Unauthorized'}), 401
 

services/token_service.py

@@ -1,73 +1,121 @@
 """
 Token and student progress operations backed by CSV file.
+Optimized with in-memory caching and cross-process file locking.
 """
 
 import csv
 import logging
 import os
+import fcntl
+import threading
+from typing import Dict, List, Optional, Tuple
 
 from config import TOKENS_FILE
 
+# Global cache and synchronization for the current process
+_cache_lock = threading.Lock()
+_cached_tokens: Dict[str, dict] = {}
+_cached_mtime: float = 0.0
+_cached_fieldnames: List[str] = []
+
+
+def _load_tokens_safely() -> Tuple[Dict[str, dict], List[str]]:
+    """Load tokens from CSV with file locking and return (tokens_dict, fieldnames)."""
+    if not os.path.exists(TOKENS_FILE):
+        return {}, []
+
+    try:
+        with open(TOKENS_FILE, 'r', newline='', encoding='utf-8') as f:
+            # Acquire shared lock for reading (blocks if an exclusive lock is held)
+            fcntl.flock(f.fileno(), fcntl.LOCK_SH)
+            try:
+                reader = csv.DictReader(f, delimiter=';')
+                fieldnames = reader.fieldnames or []
+                # Use a dictionary for O(1) lookups by token
+                tokens = {row['token']: row for row in reader if 'token' in row}
+                return tokens, fieldnames
+            finally:
+                fcntl.flock(f.fileno(), fcntl.LOCK_UN)
+    except Exception as e:
+        logging.error(f"Error loading tokens file: {e}")
+        return {}, []
+
+
+def _get_tokens() -> Tuple[Dict[str, dict], List[str]]:
+    """Get tokens from cache or reload if file has changed on disk."""
+    global _cached_tokens, _cached_mtime, _cached_fieldnames
+    
+    if not os.path.exists(TOKENS_FILE):
+        return {}, []
+
+    try:
+        current_mtime = os.path.getmtime(TOKENS_FILE)
+    except OSError:
+        return {}, []
+    
+    with _cache_lock:
+        if current_mtime > _cached_mtime:
+            # File has been modified by this or another process
+            new_tokens, new_fieldnames = _load_tokens_safely()
+            if new_tokens: # Only update if we successfully read something
+                _cached_tokens = new_tokens
+                _cached_fieldnames = new_fieldnames
+                _cached_mtime = current_mtime
+                logging.debug(f"Reloaded {len(_cached_tokens)} tokens from {TOKENS_FILE}")
+            
+        return _cached_tokens, _cached_fieldnames
+
 
 def get_teacher_token():
     """Return the teacher token (first data row in CSV)."""
-    if not os.path.exists(TOKENS_FILE):
+    tokens, _ = _get_tokens()
-        return None
+    if not tokens:
-
-    with open(TOKENS_FILE, 'r', newline='', encoding='utf-8') as csvfile:
-        reader = csv.DictReader(csvfile, delimiter=';')
-        for row in reader:
-            return row['token']
-
         return None
+    # Python 3.7+ preserves insertion order in dicts
+    return next(iter(tokens.keys()))
 
 
 def is_teacher_token(token):
-    """Check if the given token belongs to the teacher (first row)."""
+    """Check if the given token belongs to the teacher."""
     return token == get_teacher_token()
 
 
 def validate_token(token):
-    """Validate if a token exists in the CSV file and return student info."""
+    """Validate if a token exists and return student info."""
-    if not os.path.exists(TOKENS_FILE):
+    if not token:
         return None
-
+    tokens, _ = _get_tokens()
-    with open(TOKENS_FILE, 'r', newline='', encoding='utf-8') as csvfile:
+    row = tokens.get(token)
-        reader = csv.DictReader(csvfile, delimiter=';')
+    if row:
-        for row in reader:
-            if row['token'] == token:
         return {
             'token': row['token'],
             'student_name': row['nama_siswa'],
             'is_teacher': is_teacher_token(token),
         }
-
     return None
 
 
 def get_student_progress(token):
     """Get the progress of a student based on their token."""
-    if not os.path.exists(TOKENS_FILE):
+    if not token:
-        return None
-
-    with open(TOKENS_FILE, 'r', newline='', encoding='utf-8') as csvfile:
-        reader = csv.DictReader(csvfile, delimiter=';')
-        for row in reader:
-            if row['token'] == token:
-                return row
-
         return None
+    tokens, _ = _get_tokens()
+    return tokens.get(token)
 
 
 def update_student_progress(token, lesson_name, status="completed"):
-    """Update the progress of a student for a specific lesson."""
+    """Update the progress of a student for a specific lesson with cross-process locking."""
     if not os.path.exists(TOKENS_FILE):
         logging.warning(f"Tokens file {TOKENS_FILE} does not exist")
         return False
 
-    rows = []
+    # Use 'r+' to allow reading and writing in the same file handle with one lock
-    with open(TOKENS_FILE, 'r', newline='', encoding='utf-8') as csvfile:
+    try:
-        reader = csv.DictReader(csvfile, delimiter=';')
+        with open(TOKENS_FILE, 'r+', newline='', encoding='utf-8') as f:
+            # Acquire exclusive lock for the whole read-modify-write cycle
+            fcntl.flock(f.fileno(), fcntl.LOCK_EX)
+            try:
+                reader = csv.DictReader(f, delimiter=';')
                 fieldnames = reader.fieldnames
                 rows = list(reader)
                 
@@ -79,29 +127,40 @@ def update_student_progress(token, lesson_name, status="completed"):
                             updated = True
                             logging.info(f"Updating progress for token {token}, lesson {lesson_name}, status {status}")
                         else:
-                logging.warning(f"Lesson '{lesson_name}' not found in CSV columns: {fieldnames}")
+                            logging.warning(f"Lesson '{lesson_name}' not found in CSV columns")
                         break
                 
                 if updated:
-        with open(TOKENS_FILE, 'w', newline='', encoding='utf-8') as csvfile:
+                    # Clear and write back
-            writer = csv.DictWriter(csvfile, fieldnames=fieldnames, delimiter=';')
+                    f.seek(0)
+                    f.truncate()
+                    writer = csv.DictWriter(f, fieldnames=fieldnames, delimiter=';')
                     writer.writeheader()
                     writer.writerows(rows)
-        logging.info(f"Updated progress for token {token}, lesson {lesson_name}, status {status}")
+                    f.flush()
+                    os.fsync(f.fileno()) # Guarantee write to disk
+                    return True
                 else:
-        logging.warning(f"Failed to update progress for token {token}, lesson {lesson_name}")
+                    return False
-
+            finally:
-    return updated
+                fcntl.flock(f.fileno(), fcntl.LOCK_UN)
+    except Exception as e:
+        logging.error(f"Error updating student progress: {e}")
+        return False
 
 
 def initialize_tokens_file(lesson_names):
     """Initialize the tokens CSV file with headers and lesson columns."""
     if not os.path.exists(TOKENS_FILE):
         headers = ['token', 'nama_siswa'] + lesson_names
+        try:
             with open(TOKENS_FILE, 'w', newline='', encoding='utf-8') as csvfile:
+                # No lock needed for initial creation
                 writer = csv.writer(csvfile, delimiter=';')
                 writer.writerow(headers)
             print(f"Created new tokens file: {TOKENS_FILE} with headers: {headers}")
+        except Exception as e:
+            logging.error(f"Error initializing tokens file: {e}")
 
 
 def calculate_student_completion(student_data, all_lessons):
@@ -119,20 +178,15 @@ def calculate_student_completion(student_data, all_lessons):
 
 
 def get_all_students_progress(all_lessons_func):
-    """Get all students' progress data for the progress report.
+    """Get all students' progress data for the progress report."""
-
-    Returns (all_students_progress, ordered_lessons).
-    """
     all_students_progress = []
     ordered_lessons = []
-    lesson_headers = []
 
-    if not os.path.exists(TOKENS_FILE):
+    tokens, fieldnames = _get_tokens()
+    if not tokens:
         return all_students_progress, ordered_lessons
 
-    with open(TOKENS_FILE, 'r', newline='', encoding='utf-8') as csvfile:
+    lesson_headers = [field for field in fieldnames if field not in ['token', 'nama_siswa']]
-        reader = csv.DictReader(csvfile, delimiter=';')
-        lesson_headers = [field for field in reader.fieldnames if field not in ['token', 'nama_siswa']]
 
     all_lessons_dict = {}
     for lesson in all_lessons_func():
@@ -149,10 +203,13 @@ def get_all_students_progress(all_lessons_func):
                 'description': 'Lesson information not available',
             })
 
-        for row in reader:
+    for row in tokens.values():
         student_data = dict(row)
-            del student_data['token']
+        # Don't delete 'token' from the original dict in cache!
-            student_data['completed_count'] = calculate_student_completion(student_data, ordered_lessons)
+        student_data_copy = student_data.copy()
-            all_students_progress.append(student_data)
+        if 'token' in student_data_copy:
+            del student_data_copy['token']
+        student_data_copy['completed_count'] = calculate_student_completion(student_data_copy, ordered_lessons)
+        all_students_progress.append(student_data_copy)
 
     return all_students_progress, ordered_lessons