fix(retries): change default retry_interval to 1 second (was 0.1) (#122)

This commit changes the default value of the retry_interval
parameter (in the BaseService.enable_retries method) from 0.1
to 1.0.   This will result in default retry intervals
of 1, 2, 4, 8, ... seconds instead of 0.1, 0.2, 0.4, 0.8, ... seconds.
This change will align the python core retry support with Go.
Also added some detailed info in the docstring for the method as well.

ibm_cloud_sdk_core/base_service.py

@@ -97,16 +97,26 @@ def __init__(self,
         if not isinstance(self.authenticator, Authenticator):
             raise ValueError('authenticator should be of type Authenticator')
 
-    def enable_retries(self, max_retries: int = 4, retry_interval: float = 0.1) -> None:
-        """Setup http_client with retry_config and http_adapter"""
+    def enable_retries(self, max_retries: int = 4, retry_interval: float = 1.0) -> None:
+        """Enable automatic retries on the underlying http client used by the BaseService instance.
+
+        Args:
+          max_retries: the maximum number of retries to attempt for a failed retryable request
+          retry_interval: the default wait time (in seconds) to use for the first retry attempt.
+            In general, if a response includes the Retry-After header, that will be used for
+            the wait time associated with the retry attempt.  If the Retry-After header is not
+            present, then the wait time is based on the retry_interval and retry attempt number:
+               wait_time = retry_interval * (2 ^ (n-1)), where n is the retry attempt number
+        """
         self.retry_config = Retry(
-            total = max_retries,
-            backoff_factor = retry_interval,
+            total=max_retries,
+            backoff_factor=retry_interval,
             # List of HTTP status codes to retry on in addition to Timeout/Connection Errors
-            status_forcelist = [429, 500, 502, 503, 504],
+            status_forcelist=[429, 500, 502, 503, 504],
             # List of HTTP methods to retry on
             # Omitting this will default to all methods except POST
-            allowed_methods=['HEAD', 'GET', 'PUT', 'DELETE', 'OPTIONS', 'TRACE', 'POST']
+            allowed_methods=['HEAD', 'GET', 'PUT',
+                             'DELETE', 'OPTIONS', 'TRACE', 'POST']
         )
         self.http_adapter = HTTPAdapter(max_retries=self.retry_config)
         self.http_client.mount('http://', self.http_adapter)
@@ -163,7 +173,8 @@ def configure_service(self, service_name: str) -> None:
                 if config.get('MAX_RETRIES'):
                     kwargs["max_retries"] = int(config.get('MAX_RETRIES'))
                 if config.get('RETRY_INTERVAL'):
-                    kwargs["retry_interval"] = float(config.get('RETRY_INTERVAL'))
+                    kwargs["retry_interval"] = float(
+                        config.get('RETRY_INTERVAL'))
                 self.enable_retries(**kwargs)
 
     def _set_user_agent_header(self, user_agent_string: str) -> None:

test/test_base_service.py

@@ -605,7 +605,7 @@ def test_retry_config_default():
                           authenticator=NoAuthAuthenticator())
     service.enable_retries()
     assert service.retry_config.total == 4
-    assert service.retry_config.backoff_factor == 0.1
+    assert service.retry_config.backoff_factor == 1.0
     assert service.http_client.get_adapter('https://').max_retries.total == 4
 
     # Ensure retries fail after 4 retries