Pick caching backend via env vars

README.md

@@ -296,13 +296,15 @@ output = morss.FeedFormat(rss, options, 'unicode') # formats final feed
 
 ## Cache information
 
-morss uses caching to make loading faster. There are 3 possible cache backends
-(visible in `morss/crawler.py`):
+morss uses caching to make loading faster. There are 3 possible cache backends,
+which can be picked via environment variables:
 
-- `{}`: a simple python in-memory dict() object
-- `SQLiteCache`: sqlite3 cache. Default file location is in-memory (i.e. it will
-be cleared every time the program is run
-- `MySQLCacheHandler`
+- `(nothing/default)`: a simple python in-memory dict() object.
+- `CACHE=sqlite`: sqlite3 cache. Default file location is in-memory (i.e. it
+will be cleared every time the program is run). Path can be defined with
+`SQLITE_PATH`.
+- `CACHE=mysql`: MySQL cache. Connection can be defined with the following
+environment variables: `MYSQL_USER`, `MYSQL_PWD`, `MYSQL_DB`, `MYSQL_HOST`
 
 ## Configuration
 ### Length limitation

morss/cgi.py

@@ -101,8 +101,6 @@ def cgi_app(environ, start_response):
 
     headers['content-type'] += '; charset=utf-8'
 
-    crawler.default_cache = crawler.SQLiteCache(os.path.join(os.getcwd(), 'morss-cache.db'))
-
     # get the work done
     url, rss = FeedFetch(url, options)
 

morss/cli.py

@@ -2,7 +2,6 @@ import sys
 import os.path
 import argparse
 
-from . import crawler
 from .morss import FeedFetch, FeedGather, FeedFormat
 from .morss import Options
 
@@ -44,8 +43,6 @@ def cli_app():
     options = Options(vars(parser.parse_args()))
     url = options.url
 
-    crawler.default_cache = crawler.SQLiteCache(os.path.expanduser('~/.cache/morss-cache.db'))
-
     url, rss = FeedFetch(url, options)
     rss = FeedGather(rss, url, options)
     out = FeedFormat(rss, options, 'unicode')

morss/crawler.py

@@ -388,9 +388,6 @@ class HTTPRefreshHandler(BaseHandler):
     https_response = http_response
 
 
-default_cache = {}
-
-
 class CacheHandler(BaseHandler):
     " Cache based on etags/last-modified "
 
@@ -659,6 +656,22 @@ class MySQLCacheHandler(BaseCache):
                 (url,) + value + value)
 
 
+if 'CACHE' in os.environ:
+    if os.environ['CACHE'] == 'mysql':
+        default_cache = MySQLCacheHandler(
+            user = os.getenv('MYSQL_USER'),
+            password = os.getenv('MYSQL_PWD'),
+            database = os.getenv('MYSQL_DB'),
+            host = os.getenv('MYSQL_HOST')
+        )
+
+    elif os.environ['CACHE'] == 'sqlite':
+        default_cache = SQLiteCache(os.getenv('SQLITE_PATH', ':memory:'))
+
+else:
+        default_cache = {}
+
+
 if __name__ == '__main__':
     req = adv_get(sys.argv[1] if len(sys.argv) > 1 else 'https://morss.it')