Alternative approach to retry failed queries

krakenex/api.py

@@ -18,6 +18,8 @@
 """Kraken.com cryptocurrency Exchange API."""
 
 import requests
+from requests.adapters import HTTPAdapter
+from requests.packages.urllib3.util.retry import Retry
 
 # private query nonce
 import time
@@ -57,6 +59,12 @@ def __init__(self, key='', secret=''):
         :returns: None
 
         """
+
+        self._retry_config = {}
+        self._retry_config['forcelist'] = (104, 500, 502, 503, 504, 520, 521, 522, 523, 524)
+        self._retry_config['retries'] = 3
+        self._retry_config['backoff'] = 0.5
+
         self.key = key
         self.secret = secret
         self.uri = 'https://api.kraken.com'
@@ -103,7 +111,65 @@ def load_key(self, path):
             self.secret = f.readline().strip()
         return
 
-    def _query(self, urlpath, data, headers=None, timeout=None):
+
+    @property
+    def retry_config(self):
+        """ Return the current retry configuration dict as a copy
+
+            :returns: dict containing the current retry configuration
+        """
+
+        return self._retry_config.copy()
+
+
+    @retry_config.setter
+    def retry_config(self, retry_dict):
+        """ Set the internal retry configuration dict
+
+            .. note:: 
+            Does some error checking to ensure that all the keys in the new dict match with 
+            those in the original configuration dict. 
+
+            :param retry_dict: new configuration for retries
+            :type retry_dict: dict
+
+            :returns: None
+        """
+
+        if(len(retry_dict.keys()) == len(self._retry_config.keys())):
+            if all(key in retry_dict for key in self._retry_config):
+                self._retry_config = retry_dict.copy()
+
+
+    def _retry_session(self, session=None):
+        """ Low-level configuration for retries
+
+        ..note:: 
+          for documentation of this technique, refer to:
+          https://www.peterbe.com/plog/best-practice-with-retries-with-requests
+
+        :param session: Use an already existing session. If None, the session created during instantiation is used.
+        :type session: requests session object
+
+        :returns: requests session object
+        """
+
+        if not session:
+            session = self.session
+
+        retry = Retry(total=None, read=self._retry_config['retries'], connect=self._retry_config['retries'], redirect=0,
+                      status=self._retry_config['retries'], backoff_factor=self._retry_config['backoff'], 
+                      status_forcelist=self._retry_config['forcelist'],
+                      method_whitelist=frozenset(['HEAD', 'TRACE', 'GET', 'PUT', 'OPTIONS', 'DELETE', 'POST']))
+
+        adapter = HTTPAdapter(max_retries=retry)
+        session.mount('https://', adapter)
+        session.mount('http://', adapter)
+
+        return session
+
+
+    def _query(self, urlpath, data, headers=None, timeout=None, retry=False):
         """ Low-level query handling.
 
         .. note::
@@ -130,8 +196,13 @@ def _query(self, urlpath, data, headers=None, timeout=None):
             headers = {}
 
         url = self.uri + urlpath
+
+        if(retry):
+            curr_session = self._retry_session()
+        else:
+            curr_session = self.session
 
-        self.response = self.session.post(url, data = data, headers = headers,
+        self.response = curr_session.post(url, data = data, headers = headers, 
                                           timeout = timeout)
 
         if self.response.status_code not in (200, 201, 202):
@@ -140,7 +211,7 @@ def _query(self, urlpath, data, headers=None, timeout=None):
         return self.response.json(**self._json_options)
 
 
-    def query_public(self, method, data=None, timeout=None):
+    def query_public(self, method, data=None, timeout=None, retry=False):
         """ Performs an API query that does not require a valid key/secret pair.
 
         :param method: API method name
@@ -159,9 +230,9 @@ def query_public(self, method, data=None, timeout=None):
 
         urlpath = '/' + self.apiversion + '/public/' + method
 
-        return self._query(urlpath, data, timeout = timeout)
+        return self._query(urlpath, data, timeout = timeout, retry = retry)
 
-    def query_private(self, method, data=None, timeout=None):
+    def query_private(self, method, data=None, timeout=None, retry=False):
         """ Performs an API query that requires a valid key/secret pair.
 
         :param method: API method name
@@ -190,7 +261,7 @@ def query_private(self, method, data=None, timeout=None):
             'API-Sign': self._sign(data, urlpath)
         }
 
-        return self._query(urlpath, data, headers, timeout = timeout)
+        return self._query(urlpath, data, headers, timeout = timeout, retry = retry)
 
     def _nonce(self):
         """ Nonce counter.