[Config Change] Various Gravatar-related changes (#467)

* Add config option to enable/disable gravatar

This is useful when running a development instance behind a firewall
or NAT, where gravatar cannot reach you to serve up the default user
avatar.

* Pregenerate Gravatar default image URLs

If possible (i.e. SERVER_NAME is set), we can pregenerate the constant
gravatar default URL once at application startup, and re-use that,
as url_for calls are surprisingly expensive.

Especially on torrent view pages with lots of comments, this cuts down
on url_for calls massively, saving on my system about 0.3 ms per call.

config.example.py

@@ -152,3 +152,7 @@ ES_INDEX_NAME = SITE_FLAVOR
 # Time limit for editing a comment after it has been posted (seconds)
 # Set to 0 to disable
 EDITING_TIME_LIMIT = 0
+
+# Whether to use Gravatar or just always use the default avatar
+# (Useful if run as development instance behind NAT/firewall)
+ENABLE_GRAVATAR = True

nyaa/__init__.py

@@ -96,4 +96,10 @@ def create_app(config):
     app.register_blueprint(api_blueprint)
     register_views(app)
 
+    # Pregenerate some URLs to avoid repeat url_for calls
+    if 'SERVER_NAME' in app.config and app.config['SERVER_NAME']:
+        with app.app_context():
+            url = flask.url_for('static', filename='img/avatar/default.png', _external=True)
+            app.config['DEFAULT_GRAVATAR_URL'] = url
+
     return app

nyaa/models.py

@@ -518,12 +518,18 @@ class User(db.Model):
         return all(checks)
 
     def gravatar_url(self):
+        if 'DEFAULT_GRAVATAR_URL' in app.config:
+            default_url = app.config['DEFAULT_GRAVATAR_URL']
+        else:
+            default_url = flask.url_for('static', filename='img/avatar/default.png',
+                                        _external=True)
+        if app.config['ENABLE_GRAVATAR']:
             # from http://en.gravatar.com/site/implement/images/python/
             params = {
                 # Image size (https://en.gravatar.com/site/implement/images/#size)
                 's': 120,
                 # Default image (https://en.gravatar.com/site/implement/images/#default-image)
-            'd': flask.url_for('static', filename='img/avatar/default.png', _external=True),
+                'd': default_url,
                 # Image rating (https://en.gravatar.com/site/implement/images/#rating)
                 # Nyaa: PG-rated, Sukebei: X-rated
                 'r': 'pg' if app.config['SITE_FLAVOR'] == 'nyaa' else 'x',
@@ -531,6 +537,8 @@ class User(db.Model):
             # construct the url
             return 'https://www.gravatar.com/avatar/{}?{}'.format(
                 md5(self.email.encode('utf-8').lower()).hexdigest(), urlencode(params))
+        else:
+            return default_url
 
     @property
     def userlevel_str(self):