rate limit google requests

oml/meta/__init__.py

@@ -59,7 +59,11 @@ def lookup(key, value):
         return oml.metaremote.lookup(key, value)
     '''
     if key == 'isbn':
+        try:
             data = google.info(key, value)
+        except:
+            logger.debug('google.info failed %s=%s', key, value, exc_info=True)
+            data = {}
     else:
         data = {key: [value]}
         ids = set([(key, value)])

oml/meta/google.py

@@ -1,6 +1,7 @@
 # -*- coding: utf-8 -*-
 # vi:si:et:sw=4:sts=4:ts=4
 
+from time import time, sleep
 
 from ox.cache import get_json, store
 import ox.web.google
@@ -39,6 +40,9 @@ def info(key, value):
     if key not in ('isbn', 'lccn', 'oclc'):
         raise IOError('unknwon key %s' % key)
     url = 'https://www.googleapis.com/books/v1/volumes?q=%s:%s' % (key, value)
+    while not api_limit.consume(1):
+        logger.debug('hitting google api to fast, waiting 1 second')
+        sleep(1)
     r = get_json(url, timeout=-1)
     if 'error' in r:
         store.delete(url)
@@ -94,3 +98,28 @@ def info(key, value):
     data = decode_html_data(data)
     return data
 
+class Limit(object):
+
+    def __init__(self, fill_rate, capacity):
+        self.timestamp = time()
+        self.fill_rate = fill_rate
+        self.capacity = capacity
+        self._tokens = capacity
+
+    def consume(self, tokens):
+        if tokens <= self.tokens:
+            self._tokens -= tokens
+        else:
+            return False
+        return True
+
+    def get_tokens(self):
+        now = time()
+        if self._tokens < self.capacity:
+            delta = self.fill_rate * (now - self.timestamp)
+            self._tokens = min(self.capacity, self._tokens + delta)
+        self.timestamp = now
+        return self._tokens
+    tokens = property(get_tokens)
+
+api_limit = Limit(fill_rate=1, capacity=10)