Add support for connection retry

With the new optional parameter `retries` the number of retries in case of a
failure can be specified.

For compability reasons the default is kept as zero.

Change-Id: I9483343208d6f1be7b2b74ba993499c51852f431

jenkins/__init__.py

@@ -59,11 +59,13 @@ import multi_key_dict
 import requests
 import requests.exceptions as req_exc
 import urllib3.util.timeout
+from requests.adapters import HTTPAdapter
 from requests.packages.urllib3.exceptions import InsecureRequestWarning
 from http.client import BadStatusLine
 from urllib.error import URLError
 from urllib.parse import quote, urlencode, urljoin, urlparse
 import xml.etree.ElementTree as ET
+from urllib3.util import parse_url, Retry
 
 from jenkins import plugins
 
@@ -93,6 +95,7 @@ LAUNCHER_JNLP = 'hudson.slaves.JNLPLauncher'
 LAUNCHER_WINDOWS_SERVICE = 'hudson.os.windows.ManagedWindowsServiceLauncher'
 DEFAULT_HEADERS = {'Content-Type': 'text/xml; charset=utf-8'}
 DEFAULT_TIMEOUT = getattr(urllib3.util.timeout, '_DEFAULT_TIMEOUT', socket._GLOBAL_DEFAULT_TIMEOUT)
+DEFAULT_RETRIES = 0
 
 # REST Endpoints
 INFO = 'api/json'
@@ -302,7 +305,7 @@ class Jenkins(object):
     _timeout_warning_issued = False
 
     def __init__(self, url, username=None, password=None,
-                 timeout=DEFAULT_TIMEOUT):
+                 timeout=DEFAULT_TIMEOUT, retries=DEFAULT_RETRIES):
         '''Create handle to Jenkins instance.
 
         All methods will raise :class:`JenkinsException` on failure.
@@ -336,6 +339,11 @@ class Jenkins(object):
         self.timeout = timeout
         self._session = WrappedSession()
 
+        self._session.mount(
+            parse_url(self.server).scheme,
+            HTTPAdapter(max_retries=Retry(total=retries, backoff_factor=0.1))
+        )
+
         extra_headers = os.environ.get("JENKINS_API_EXTRA_HEADERS", "")
         if extra_headers:
             logging.warning("JENKINS_API_EXTRA_HEADERS adds these HTTP headers: %s", extra_headers.split("\n"))