Merge pull request #5 from ekampf/feature/transport-error-retry

Client support for retrying requests

Author: syrusakbary

.travis.yml

@@ -7,7 +7,7 @@ python:
 - 3.5
 cache: pip
 install:
-- pip install pytest pytest-cov coveralls flake8
+- pip install -r ./dev_requirements.txt
 - pip install -e .
 script:
 - flake8 gql

dev_requirements.txt

@@ -0,0 +1,5 @@
+pytest
+pytest-cov
+coveralls
+flake8
+mock

gql/client.py

@@ -1,13 +1,22 @@
+import logging
+
 from graphql import parse, introspection_query, build_ast_schema, build_client_schema
 from graphql.validation import validate
 
 from .transport.local_schema import LocalSchemaTransport
 
 
-class Client(object):
+class RetryError(Exception):
+    """Custom exception thrown when retry logic fails"""
+    def __init__(self, retries_count, last_exception):
+        message = "Failed %s retries: %s" % (retries_count, last_exception)
+        super(RetryError, self).__init__(message)
+        self.last_exception = last_exception
+
 
+class Client(object):
     def __init__(self, schema=None, introspection=None, type_def=None, transport=None,
-                 fetch_schema_from_transport=False):
+                 fetch_schema_from_transport=False, retries=0):
         assert not(type_def and introspection), 'Cant provide introspection type definition at the same time'
         if transport and fetch_schema_from_transport:
             assert not schema, 'Cant fetch the schema from transport if is already provided'
@@ -25,6 +34,7 @@ def __init__(self, schema=None, introspection=None, type_def=None, transport=Non
         self.schema = schema
         self.introspection = introspection
         self.transport = transport
+        self.retries = retries
 
     def validate(self, document):
         if not self.schema:
@@ -36,7 +46,28 @@ def validate(self, document):
     def execute(self, document, *args, **kwargs):
         if self.schema:
             self.validate(document)
-        result = self.transport.execute(document, *args, **kwargs)
+
+        result = self._get_result(document, *args, **kwargs)
         if result.errors:
             raise result.errors[0]
+
         return result.data
+
+    def _get_result(self, document, *args, **kwargs):
+        if not self.retries:
+            return self.transport.execute(document, *args, **kwargs)
+
+        last_exception = None
+        retries_count = 0
+        while retries_count < self.retries:
+            try:
+                result = self.transport.execute(document, *args, **kwargs)
+                return result
+            except Exception as e:
+                last_exception = e
+                logging.warn("Request failed with exception %s. Retrying for the %s time...",
+                             e, retries_count + 1, exc_info=True)
+            finally:
+                retries_count += 1
+
+        raise RetryError(retries_count, last_exception)

gql/transport/requests.py

@@ -8,21 +8,33 @@
 
 
 class RequestsHTTPTransport(HTTPTransport):
-    def __init__(self, url, auth=None, **kwargs):
+    def __init__(self, url, auth=None, use_json=False, timeout=None, **kwargs):
+        """
+        :param url: The GraphQL URL
+        :param auth: Auth tuple or callable to enable Basic/Digest/Custom HTTP Auth
+        :param use_json: Send request body as JSON instead of form-urlencoded
+        :param timeout: Specifies a default timeout for requests (Default: None)
+        """
         super(RequestsHTTPTransport, self).__init__(url, **kwargs)
         self.auth = auth
+        self.default_timeout = timeout
+        self.use_json = use_json
 
-    def execute(self, document, variable_values=None):
+    def execute(self, document, variable_values=None, timeout=None):
         query_str = print_ast(document)
-        request = requests.post(
-            self.url,
-            data={
-                'query': query_str,
-                'variables': variable_values
-            },
-            headers=self.headers,
-            auth=self.auth
-        )
+        payload = {
+            'query': query_str,
+            'variables': variable_values or {}
+        }
+
+        data_key = 'json' if self.use_json else 'data'
+        post_args = {
+            'headers': self.headers,
+            'auth': self.auth,
+            'timeout': timeout or self.default_timeout,
+            data_key: payload
+        }
+        request = requests.post(self.url, **post_args)
         request.raise_for_status()
 
         result = request.json()

setup.py

@@ -29,5 +29,5 @@
         'graphql-core>=0.5.0',
         'promise>=0.4.0'
     ],
-    tests_require=['pytest>=2.7.2'],
+    tests_require=['pytest>=2.7.2', 'mock'],
 )

tests/test_client.py

@@ -0,0 +1,34 @@
+import pytest
+import mock
+
+from gql import Client, gql
+from gql.transport.requests import RequestsHTTPTransport
+
+
+@mock.patch('gql.transport.requests.RequestsHTTPTransport.execute')
+def test_retries(execute_mock):
+    expected_retries = 3
+    execute_mock.side_effect =Exception("fail")
+
+    client = Client(
+        retries=expected_retries,
+        transport=RequestsHTTPTransport(url='http://swapi.graphene-python.org/graphql')
+    )
+
+    query = gql('''
+    {
+      myFavoriteFilm: film(id:"RmlsbToz") {
+        id
+        title
+        episodeId
+      }
+    }
+    ''')
+
+    with pytest.raises(Exception):
+        client.execute(query)
+
+    assert execute_mock.call_count == expected_retries
+
+
+