Add translation cache for faster repeated translations (5000 entry LRU cache with hit rate tracking)

main.py

@@ -21,6 +21,7 @@ import time
 from config import config
 from translators import excel_translator, word_translator, pptx_translator
 from utils import file_handler, handle_translation_error, DocumentProcessingError
+from services.translation_service import _translation_cache
 
 # Import auth routes
 from routes.auth_routes import router as auth_router
@@ -228,7 +229,8 @@ async def health_check():
             "rate_limits": {
                 "requests_per_minute": rate_limit_config.requests_per_minute,
                 "translations_per_minute": rate_limit_config.translations_per_minute,
-            }
+            },
+            "translation_cache": _translation_cache.stats()
         }
     )
 

services/translation_service.py

@@ -1,7 +1,7 @@
 """
 Translation Service Abstraction
 Provides a unified interface for different translation providers
-Optimized for high performance with parallel processing
+Optimized for high performance with parallel processing and caching
 """
 from abc import ABC, abstractmethod
 from typing import Optional, List, Dict, Tuple
@@ -13,12 +13,77 @@ import threading
 import asyncio
 from functools import lru_cache
 import time
+import hashlib
+from collections import OrderedDict
 
 
 # Global thread pool for parallel translations
 _executor = concurrent.futures.ThreadPoolExecutor(max_workers=8)
 
 
+class TranslationCache:
+    """Thread-safe LRU cache for translations to avoid redundant API calls"""
+    
+    def __init__(self, maxsize: int = 5000):
+        self.cache: OrderedDict = OrderedDict()
+        self.maxsize = maxsize
+        self.lock = threading.RLock()
+        self.hits = 0
+        self.misses = 0
+    
+    def _make_key(self, text: str, target_language: str, source_language: str, provider: str) -> str:
+        """Create a unique cache key"""
+        content = f"{provider}:{source_language}:{target_language}:{text}"
+        return hashlib.md5(content.encode('utf-8')).hexdigest()
+    
+    def get(self, text: str, target_language: str, source_language: str, provider: str) -> Optional[str]:
+        """Get a cached translation if available"""
+        key = self._make_key(text, target_language, source_language, provider)
+        with self.lock:
+            if key in self.cache:
+                self.hits += 1
+                # Move to end (most recently used)
+                self.cache.move_to_end(key)
+                return self.cache[key]
+            self.misses += 1
+            return None
+    
+    def set(self, text: str, target_language: str, source_language: str, provider: str, translation: str):
+        """Cache a translation result"""
+        key = self._make_key(text, target_language, source_language, provider)
+        with self.lock:
+            if key in self.cache:
+                self.cache.move_to_end(key)
+            self.cache[key] = translation
+            # Remove oldest if exceeding maxsize
+            while len(self.cache) > self.maxsize:
+                self.cache.popitem(last=False)
+    
+    def clear(self):
+        """Clear the cache"""
+        with self.lock:
+            self.cache.clear()
+            self.hits = 0
+            self.misses = 0
+    
+    def stats(self) -> Dict:
+        """Get cache statistics"""
+        with self.lock:
+            total = self.hits + self.misses
+            hit_rate = (self.hits / total * 100) if total > 0 else 0
+            return {
+                "size": len(self.cache),
+                "maxsize": self.maxsize,
+                "hits": self.hits,
+                "misses": self.misses,
+                "hit_rate": f"{hit_rate:.1f}%"
+            }
+
+
+# Global translation cache
+_translation_cache = TranslationCache(maxsize=5000)
+
+
 class TranslationProvider(ABC):
     """Abstract base class for translation providers"""
     
@@ -63,10 +128,11 @@ class TranslationProvider(ABC):
 
 
 class GoogleTranslationProvider(TranslationProvider):
-    """Google Translate implementation with batch support"""
+    """Google Translate implementation with batch support and caching"""
     
     def __init__(self):
         self._local = threading.local()
+        self.provider_name = "google"
     
     def _get_translator(self, source_language: str, target_language: str) -> GoogleTranslator:
         """Get or create a translator instance for the current thread"""
@@ -81,9 +147,17 @@ class GoogleTranslationProvider(TranslationProvider):
         if not text or not text.strip():
             return text
         
+        # Check cache first
+        cached = _translation_cache.get(text, target_language, source_language, self.provider_name)
+        if cached is not None:
+            return cached
+        
         try:
             translator = self._get_translator(source_language, target_language)
-            return translator.translate(text)
+            result = translator.translate(text)
+            # Cache the result
+            _translation_cache.set(text, target_language, source_language, self.provider_name, result)
+            return result
         except Exception as e:
             print(f"Translation error: {e}")
             return text
@@ -91,7 +165,7 @@ class GoogleTranslationProvider(TranslationProvider):
     def translate_batch(self, texts: List[str], target_language: str, source_language: str = 'auto', batch_size: int = 50) -> List[str]:
         """
         Translate multiple texts using batch processing for speed.
-        Uses deep_translator's batch capability when possible.
+        Uses caching to avoid redundant translations.
         """
         if not texts:
             return []
@@ -100,15 +174,24 @@ class GoogleTranslationProvider(TranslationProvider):
         results = [''] * len(texts)
         non_empty_indices = []
         non_empty_texts = []
+        texts_to_translate = []
+        indices_to_translate = []
         
         for i, text in enumerate(texts):
             if text and text.strip():
+                # Check cache first
+                cached = _translation_cache.get(text, target_language, source_language, self.provider_name)
+                if cached is not None:
+                    results[i] = cached
+                else:
                     non_empty_indices.append(i)
                     non_empty_texts.append(text)
+                    texts_to_translate.append(text)
+                    indices_to_translate.append(i)
             else:
                 results[i] = text if text else ''
         
-        if not non_empty_texts:
+        if not texts_to_translate:
             return results
         
         try:
@@ -116,8 +199,8 @@ class GoogleTranslationProvider(TranslationProvider):
             
             # Process in batches
             translated_texts = []
-            for i in range(0, len(non_empty_texts), batch_size):
-                batch = non_empty_texts[i:i + batch_size]
+            for i in range(0, len(texts_to_translate), batch_size):
+                batch = texts_to_translate[i:i + batch_size]
                 try:
                     # Use translate_batch if available
                     if hasattr(translator, 'translate_batch'):
@@ -145,16 +228,19 @@ class GoogleTranslationProvider(TranslationProvider):
                         except:
                             translated_texts.append(text)
             
-            # Map back to original positions
-            for idx, translated in zip(non_empty_indices, translated_texts):
-                results[idx] = translated if translated else texts[idx]
+            # Map back to original positions and cache results
+            for idx, (original, translated) in zip(indices_to_translate, zip(texts_to_translate, translated_texts)):
+                result = translated if translated else texts[idx]
+                results[idx] = result
+                # Cache successful translations
+                _translation_cache.set(texts[idx], target_language, source_language, self.provider_name, result)
             
             return results
             
         except Exception as e:
             print(f"Batch translation failed: {e}")
             # Fallback to individual translations
-            for idx, text in zip(non_empty_indices, non_empty_texts):
+            for idx, text in zip(indices_to_translate, texts_to_translate):
                 try:
                     results[idx] = GoogleTranslator(source=source_language, target=target_language).translate(text) or text
                 except: