[NetApp] Fix lack of retry HTTP requests

The driver HTTP requester is not handling connection error with some
retries for avoiding temporary network failure in name resolution.
This patch adds a custom `HTTPAdapter` with 5 retries, according to
urrlib3 documentation [1]. Also, the connection retry will be visible
in the log [2].

[1] https://urllib3.readthedocs.io/en/latest/reference/urllib3.util.html#module-urllib3.util.retry
[2] https://paste.opendev.org/show/bIcwjk91d4vy5Hnxxs4Z/

Closes-Bug: #1971542
Change-Id: Ic9ff8208f10df9dbed09717d6b218f6293d2338a

manila/share/drivers/netapp/dataontap/client/api.py

@@ -25,7 +25,9 @@ from lxml import etree
 from oslo_log import log
 from oslo_serialization import jsonutils
 import requests
+from requests.adapters import HTTPAdapter
 from requests import auth
+from requests.packages.urllib3.util.retry import Retry
 
 from manila import exception
 from manila.i18n import _
@@ -227,6 +229,11 @@ class BaseClient(object):
             auth_handler = self._create_certificate_auth_handler()
 
         self._session = requests.Session()
+
+        max_retries = Retry(total=5, connect=5, read=2, backoff_factor=1)
+        adapter = HTTPAdapter(max_retries=max_retries)
+        self._session.mount('%s://' % self._protocol, adapter)
+
         self._session.auth = auth_handler
         self._session.verify = self._ssl_verify
         headers = self._build_headers()
@@ -329,6 +336,8 @@ class ZapiClient(BaseClient):
             self._build_session()
         try:
             if hasattr(self, '_timeout'):
+                if self._timeout is None:
+                    self._timeout = 10
                 response = self._session.post(
                     self._get_url(), data=request_d, timeout=self._timeout)
             else:

releasenotes/notes/netapp-retry-requests-0a77a31f5222d4b2.yaml

@@ -0,0 +1,8 @@
+---
+fixes:
+  - |
+    Sometimes NetApp API call fails due to name resolution(DNS) issue. In
+    such case, a client will now make 5 retries on connect and 2 on read
+    calls. Also, the connection retry will be visible in the log. For more
+    details, please refer to
+    `launchpad bug #1971542 <https://bugs.launchpad.net/manila/+bug/1971542>`_