api: rework _query() retries code with suggestions from PR #65.

Author: veox

krakenex/api.py

@@ -67,8 +67,13 @@ def __init__(self, key='', secret=''):
             'User-Agent': 'krakenex/' + version.__version__ + ' (+' + version.__url__ + ')'
         })
         self.response = None
-        # How many times we try to recover from bad HTTP connection situation
-        self.bad_http_connection_retries = 3
+
+        # retry-on-failure configuration
+        self.retries = 1
+        self.cooldown = 15
+        self.successcodes = [200, 201, 202]
+        self.retrycodes = [504, 520]
+
         return
 
     def close(self):
@@ -121,23 +126,24 @@ def _query(self, urlpath, data, headers=None):
 
         url = self.uri + urlpath
 
-        # Retries mechanism for certain HTTP codes. 
-        # Kraken is behind CloudFlare which adds to network requests instability during peaks
-        # Careful! Sometimes service returns error code but actuallu executes a request
-        # needs investigation if this can cause a multiple buys/sells (don't think so as there is nonce in each request )
-        attempt = 1
-        while attempt<=self.bad_http_connection_retries:
+        attempt = 0
+        while attempt < self.retries:
+            logger.debug('Posting query: nonce %d, attempt %d.', data['nonce'], attempt)
             self.response = self.session.post(url, data = data, headers = headers)
+            status = self.response.status_code
 
-            if self.response.status_code in (200, 201, 202):
-                return self.response.json()
-            elif self.response.status_code in (504, 520) and attempt<self.bad_http_connection_retries:
-                logger.debug("HTTP Error. Status Code %d. Attempting to reconnect (attempt: %d)", self.response.status_code, attempt)
-                attempt = attempt + 1
+            if status in self.successcodes:
+                break
+            elif status in self.retrycodes and attempt < self.retries:
+                logger.debug('HTTP error %d', status)
+                logger.debug('Sleeping for %d seconds', self.cooldown)
+                time.sleep(self.cooldown)
+                attempt += 1
             else:
-                # Raises stored HTTPError, if one occurred.
                 self.response.raise_for_status()
 
+        return self.response.json()
+
     def query_public(self, method, data=None):
         """ Performs an API query that does not require a valid key/secret pair.