feat: add Redis caching to TTS API for performance optimization

- Integrate Railway Redis for permanent TTS response caching
- Cache audio files as base64 encoded data with unique keys
- Implement graceful fallback when Redis is unavailable
- Add cache hit/miss headers for monitoring
- Reduce server load and improve response times

Author: thehimel

.env_template

@@ -17,3 +17,4 @@ COOKIES_MAX_AGE_IN_DAYS='2'
 OPENAI_API_KEY=''
 
 API_URL='http://127.0.0.1:8000'
+REDIS_URL='redis://localhost:6379'

src/apps/speech/views.py

@@ -1,5 +1,10 @@
+import hashlib
+import base64
+import os
 from io import BytesIO
 
+import redis
+from django.conf import settings
 from django.http import FileResponse
 from drf_yasg.utils import swagger_auto_schema
 from gtts import gTTS
@@ -10,6 +15,20 @@
 from apps.api.utils import serializer_to_manual_parameters
 from apps.speech.serializers import TextToSpeechSerializer
 
+# Redis connection setup
+try:
+    redis_url = os.getenv('REDIS_URL') or getattr(settings, 'REDIS_URL', None)
+    if redis_url:
+        redis_client = redis.from_url(redis_url, decode_responses=False)  # Keep as False for binary data
+        redis_client.ping()  # Test connection
+        REDIS_AVAILABLE = True
+    else:
+        redis_client = None
+        REDIS_AVAILABLE = False
+except (redis.ConnectionError, AttributeError):
+    redis_client = None
+    REDIS_AVAILABLE = False
+
 
 class TextToSpeechAPIView(APIView):
     @swagger_auto_schema(manual_parameters=serializer_to_manual_parameters(TextToSpeechSerializer))
@@ -23,18 +42,57 @@ def get(self, request, *args, **kwargs):
         if not input_text:
             return Response({"error": "The text parameter is missing."}, status=status.HTTP_400_BAD_REQUEST)
 
+        # Create cache key from text, language, and slow parameter
         slow = False if language == "bn" else True
+        cache_data = f"{input_text}_{language}_{slow}"
+        cache_key = f"tts:{hashlib.md5(cache_data.encode('utf-8')).hexdigest()}"
+
+        # Try to get from Redis cache first
+        if REDIS_AVAILABLE and redis_client:
+            try:
+                cached_audio = redis_client.get(cache_key)
+                if cached_audio:
+                    # Convert base64 back to bytes
+                    audio_data = base64.b64decode(cached_audio)
+                    output_file = BytesIO(audio_data)
 
+                    response = FileResponse(output_file, content_type="audio/mpeg")
+                    response["Content-Disposition"] = 'attachment; filename="output.mp3"'
+                    response["X-Cache-Status"] = "HIT"
+                    return response
+            except redis.RedisError:
+                # If Redis fails, continue without caching
+                pass
+
+        # Generate TTS if not in cache
         try:
             tts = gTTS(text=input_text, lang=language, slow=slow)
 
             output_file = BytesIO()
             tts.write_to_fp(output_file)
             output_file.seek(0)
 
+            # Read audio data for caching
+            audio_data = output_file.read()
+            output_file.seek(0)  # Reset for response
+
+            # Cache the audio data in Redis permanently
+            if REDIS_AVAILABLE and redis_client:
+                try:
+                    # Encode binary data as base64 for Redis storage
+                    encoded_audio = base64.b64encode(audio_data).decode('utf-8')
+
+                    # Cache forever - TTS results never change
+                    redis_client.set(cache_key, encoded_audio)
+                except redis.RedisError:
+                    # If caching fails, continue serving the response
+                    pass
+
             response = FileResponse(output_file, content_type="audio/mpeg")
             response["Content-Disposition"] = 'attachment; filename="output.mp3"'
+            response["X-Cache-Status"] = "MISS"
             return response
+
         except Exception as e:
             return Response(
                 {"error": f"Error generating audio: {str(e)}"}, status=status.HTTP_500_INTERNAL_SERVER_ERROR

src/core/settings.py

@@ -226,3 +226,17 @@
 SITE_ID = 1
 
 OPENAI_API_KEY = config("OPENAI_API_KEY", default="")
+
+# Redis Configuration for Railway TTS Caching
+REDIS_URL = config("REDIS_URL", default="redis://localhost:6379")
+
+# Optional: Django Cache Framework with Redis (for other caching needs)
+CACHES = {
+    'default': {
+        'BACKEND': 'django.core.cache.backends.redis.RedisCache',
+        'LOCATION': REDIS_URL,
+        'OPTIONS': {
+            'CLIENT_CLASS': 'django_redis.client.DefaultClient',
+        }
+    }
+}

src/requirements.txt

@@ -26,3 +26,4 @@ setuptools>=71.1.0
 gTTS>=2.5.1
 # googletrans==4.0.0-rc1
 openai>=1.41.1
+redis>=6.2.0