Add RedisCacheHandler (#747)

* add RedisCacheHandler

* add the explanation for customized chache handlers

* update the dependency and chengelog

CHANGELOG.md

@@ -7,7 +7,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## Unreleased
 
-// Add your changes here and then delete this line
+### Added
+* Added `RedisCacheHandler`, a cache handler that stores the token info in Redis.
 
 ## [2.19.0] - 2021-08-12
 

docs/index.rst

@@ -231,6 +231,11 @@ The custom cache handler would need to be a class that inherits from the base
 cache handler ``CacheHandler``. The default cache handler ``CacheFileHandler`` is a good example.
 An instance of that new class can then be passed as a parameter when
 creating ``SpotifyOAuth``, ``SpotifyPKCE`` or ``SpotifyImplicitGrant``.
+The following handlers are available and defined in the URL above.
+  - ``CacheFileHandler``
+  - ``MemoryCacheHandler``
+  - ``DjangoSessionCacheHandler``
+  - ``RedisCacheHandler``
 
 Feel free to contribute new cache handlers to the repo.
 

setup.py

@@ -26,6 +26,7 @@ setup(
     author_email="paul@echonest.com",
     url='https://spotipy.readthedocs.org/',
     install_requires=[
+        'redis>=3.5.3',
         'requests>=2.25.0',
         'six>=1.15.0',
         'urllib3>=1.26.0'

spotipy/cache_handler.py

@@ -1,4 +1,9 @@
-__all__ = ['CacheHandler', 'CacheFileHandler', 'DjangoSessionCacheHandler', 'MemoryCacheHandler']
+__all__ = [
+    'CacheHandler',
+    'CacheFileHandler',
+    'DjangoSessionCacheHandler',
+    'MemoryCacheHandler',
+    'RedisCacheHandler']
 
 import errno
 import json
@@ -6,6 +11,8 @@ import logging
 import os
 from spotipy.util import CLIENT_CREDS_ENV_VARS
 
+from redis import RedisError
+
 logger = logging.getLogger(__name__)
 
 
@@ -138,3 +145,32 @@ class DjangoSessionCacheHandler(CacheHandler):
             self.request.session['token_info'] = token_info
         except Exception as e:
             logger.warning("Error saving token to cache: " + str(e))
+
+
+class RedisCacheHandler(CacheHandler):
+    """
+    A cache handler that stores the token info in the Redis.
+    """
+
+    def __init__(self, redis):
+        """
+        Parameters:
+            * redis: Redis object provided by redis-py library
+            (https://github.com/redis/redis-py)
+        """
+        self.redis = redis
+
+    def get_cached_token(self):
+        token_info = None
+        try:
+            token_info = json.loads(self.redis.get('token_info'))
+        except RedisError as e:
+            logger.warning('Error getting token from cache: ' + str(e))
+
+        return token_info
+
+    def save_token_to_cache(self, token_info):
+        try:
+            self.redis.set('token_info', json.dumps(token_info))
+        except RedisError as e:
+            logger.warning('Error saving token to cache: ' + str(e))