Merge pull request #1906 from basilfx/ratelimit

Initial version of rate limiting on requests

data/interfaces/default/searchresults.html

@@ -38,7 +38,7 @@
                 %>
 				<tr class="grade${grade}">
 				%if type == 'album':
-					<td id="albumart" style=" text-align: center; vertical-align: middle;"><div id="artistImg"><img title="${result['albumid']}" class="albumArt" height="50" width="50" onerror="this.onerror=null;this.src='${caa_group_url}'"></div></td>
+					<td id="albumart" style=" text-align: center; vertical-align: middle;"><div id="artistImg"><img title="${result['albumid']}" class="albumArt" height="50" width="50" onerror="tryCCA(this, '${caa_group_url}')"></div></td>
                 %else:
 					<td id="albumart"><div id="artistImg"><img title="${result['id']}" class="albumArt" height="50" width="50"></div></td>
 				%endif
@@ -72,7 +72,13 @@
 	<script src="js/libs/jquery.dataTables.min.js"></script>
 
 	<script type="text/javascript">
-
+        function tryCCA(element, url) {
+            element.onerror = function() {
+                element.onerror = null;
+                element.src = "interfaces/default/images/no-cover-art.png";
+            };
+            element.src = url;
+        }
     	function getArt() {
     		$("table#searchresults_table tr td#albumart img").each(function(){
     			var id = $(this).attr('title');
@@ -85,7 +91,6 @@
     		});
     	}
     	function initThisPage() {
-            getArt();
     		$('#searchresults_table').dataTable({
 				"bDestroy": true,
 				"aoColumnDefs": [
@@ -103,8 +108,10 @@
 				"aaSorting": []
 			});
             $('#searchresults_table').on("draw.dt", function () {
+                getArt();
                 $("img").unveil();
             });
+            getArt();
 			resetFilters("album");
     	}
     	$(document).ready(function(){

headphones/lastfm.py

@@ -13,18 +13,23 @@
 #  You should have received a copy of the GNU General Public License
 #  along with Headphones.  If not, see <http://www.gnu.org/licenses/>.
 
-import random
 import time
+import random
+import threading
 import headphones
 
 from headphones import db, logger, request
 
 from collections import defaultdict
 
-TIMEOUT = 60 # seconds
+TIMEOUT = 60.0 # seconds
+REQUEST_LIMIT = 1.0 # seconds
 ENTRY_POINT = "http://ws.audioscrobbler.com/2.0/"
 API_KEY = "395e6ec6bb557382fc41fde867bce66f"
 
+# Required for API request limit
+lock = threading.Lock()
+
 def request_lastfm(method, **kwargs):
     """
     Call a Last.FM API method. Automatically sets the method and API key. Method
@@ -43,7 +48,8 @@ def request_lastfm(method, **kwargs):
     logger.debug("Calling Last.FM method: %s", method)
     logger.debug("Last.FM call parameters: %s", kwargs)
 
-    data = request.request_json(ENTRY_POINT, timeout=TIMEOUT, params=kwargs)
+    data = request.request_json(ENTRY_POINT, timeout=TIMEOUT, params=kwargs,
+        rate_limit=(lock, REQUEST_LIMIT))
 
     # Parse response and check for errors.
     if not data:

headphones/request.py

@@ -18,16 +18,27 @@ from headphones import logger
 from xml.dom import minidom
 from bs4 import BeautifulSoup
 
+import time
 import requests
 import feedparser
 import headphones
+import collections
+
+# Dictionary with last request times, for rate limiting.
+last_requests = collections.defaultdict(int)
 
 def request_response(url, method="get", auto_raise=True,
-    whitelist_status_code=None, **kwargs):
+    whitelist_status_code=None, rate_limit=None, **kwargs):
     """
     Convenient wrapper for `requests.get', which will capture the exceptions and
     log them. On success, the Response object is returned. In case of a
     exception, None is returned.
+
+    Additionally, there is support for rate limiting. To use this feature,
+    supply a tuple of (lock, request_limit). The lock is used to make sure no
+    other request with the same lock is executed. The request limit is the
+    minimal time between two requests (and so 1/request_limit is the number of
+    requests per seconds).
     """
 
     # Convert whitelist_status_code to a list if needed
@@ -43,9 +54,32 @@ def request_response(url, method="get", auto_raise=True,
     request_method = getattr(requests, method.lower())
 
     try:
-        # Request the URL
+        # Enfore request rate limit if applicable. This uses the lock so there
+        # is synchronized access to the API. If no limit is enforced, just do
+        # it as usual.
         logger.debug("Requesting URL via %s method: %s", method.upper(), url)
-        response = request_method(url, **kwargs)
+
+        if rate_limit:
+            lock, request_limit = rate_limit
+
+            with lock:
+                delta = time.time() - last_requests[lock]
+                limit = int(1.0 / request_limit)
+
+                if delta < request_limit:
+                    logger.debug("Sleeping %.2f seconds for request, limit " \
+                        "is %d req/sec.", request_limit - delta, limit)
+
+                    # Sleep the remaining time
+                    time.sleep(request_limit - delta)
+
+                # Update last request time and start with request. Basically, if
+                # the request takes N seconds, next request will sleep N seconds
+                # less.
+                last_requests[lock] = time.time()
+                response = request_method(url, **kwargs)
+        else:
+            response = request_method(url, **kwargs)
 
         # If status code != OK, then raise exception, except if the status code
         # is white listed.