Add support for handling multiple RMs sans Hadoop config

Also added method `get_active_host_port()` to return the address,port
tuple currently in use for the ResourceManager instance.

tests/test_hadoop_conf.py

@@ -70,7 +70,7 @@ def test_get_resource_host_port(self):
 
     @mock.patch('yarn_api_client.hadoop_conf._get_rm_ids')
     @mock.patch('yarn_api_client.hadoop_conf.parse')
-    @mock.patch('yarn_api_client.hadoop_conf._check_is_active_rm')
+    @mock.patch('yarn_api_client.hadoop_conf.check_is_active_rm')
     def test_get_resource_host_port_with_ha(self, check_is_active_rm_mock, parse_mock, get_rm_ids_mock):
         get_rm_ids_mock.return_value = ['rm1', 'rm2']
         parse_mock.return_value = 'example.com:8022'
@@ -116,17 +116,17 @@ def getheader(self, header_key, default_return):
 
         http_conn_request_mock.return_value = None
         http_getresponse_mock.return_value = ResponseMock(OK, {})
-        self.assertTrue(hadoop_conf._check_is_active_rm('example2', '8022'))
+        self.assertTrue(hadoop_conf.check_is_active_rm('example2', '8022'))
         http_getresponse_mock.reset_mock()
         http_getresponse_mock.return_value = ResponseMock(OK, {'Refresh': "testing"})
-        self.assertFalse(hadoop_conf._check_is_active_rm('example2', '8022'))
+        self.assertFalse(hadoop_conf.check_is_active_rm('example2', '8022'))
         http_getresponse_mock.reset_mock()
         http_getresponse_mock.return_value = ResponseMock(NOT_FOUND, {'Refresh': "testing"})
-        self.assertFalse(hadoop_conf._check_is_active_rm('example2', '8022'))
+        self.assertFalse(hadoop_conf.check_is_active_rm('example2', '8022'))
         http_conn_request_mock.side_effect = Exception('error')
         http_conn_request_mock.reset_mock()
         http_conn_request_mock.return_value = None
-        self.assertFalse(hadoop_conf._check_is_active_rm('example2', '8022'))
+        self.assertFalse(hadoop_conf.check_is_active_rm('example2', '8022'))
         pass
 
     def test_get_resource_manager(self):

yarn_api_client/hadoop_conf.py

@@ -29,7 +29,7 @@ def _get_resource_manager(hadoop_conf_path, rm_id=None):
         return None
 
 
-def _check_is_active_rm(rm_web_host, rm_web_port):
+def check_is_active_rm(rm_web_host, rm_web_port):
     conn = HTTPConnection(rm_web_host, rm_web_port)
     try:
         conn.request('GET', '/cluster')
@@ -52,7 +52,7 @@ def get_resource_manager_host_port():
             ret = _get_resource_manager(hadoop_conf_path, rm_id)
             if ret is not None:
                 (host, port) = ret
-                if _check_is_active_rm(host, port):
+                if check_is_active_rm(host, port):
                     return host, port
         return None
     else:

yarn_api_client/resource_manager.py

@@ -3,7 +3,7 @@
 from .base import BaseYarnAPI
 from .constants import YarnApplicationState, FinalApplicationStatus
 from .errors import IllegalArgumentError
-from .hadoop_conf import get_resource_manager_host_port
+from .hadoop_conf import get_resource_manager_host_port, check_is_active_rm, CONF_DIR
 
 
 class ResourceManager(BaseYarnAPI):
@@ -14,20 +14,38 @@ class ResourceManager(BaseYarnAPI):
     and information about applications on the cluster.
 
     If `address` argument is `None` client will try to extract `address` and
-    `port` from Hadoop configuration files.
+    `port` from Hadoop configuration files.  If both `address` and `alt_address`
+    are provided, the address corresponding to the ACTIVE HA Resource Manager will
+    be used.
 
     :param str address: ResourceManager HTTP address
     :param int port: ResourceManager HTTP port
+    :param str alt_address: Alternate ResourceManager HTTP address for HA configurations
+    :param int alt_port: Alternate ResourceManager HTTP port for HA configurations
     :param int timeout: API connection timeout in seconds
     :param boolean kerberos_enabled: Flag identifying is Kerberos Security has been enabled for YARN
     """
-    def __init__(self, address=None, port=8088, timeout=30, kerberos_enabled=False):
+    def __init__(self, address=None, port=8088, alt_address=None, alt_port=8088, timeout=30, kerberos_enabled=False):
         if address is None:
-            self.logger.debug('Get configuration from hadoop conf dir')
+            self.logger.debug('Get configuration from hadoop conf dir: {conf_dir}'.format(conf_dir=CONF_DIR))
             address, port = get_resource_manager_host_port()
+        else:
+            if alt_address:  # Determine active RM
+                if not check_is_active_rm(address, port):
+                    # Default is not active, check alternate
+                    if check_is_active_rm(alt_address, alt_port):
+                        address, port = alt_address, alt_port
 
         super(ResourceManager, self).__init__(address, port, timeout, kerberos_enabled)
 
+    def get_active_host_port(self):
+        """
+        The active address, port tuple to which this instance is associated.
+
+        :return: Tuple (str, int) corresponding to the active address and port
+        """
+        return self.address, self.port
+
     def cluster_information(self):
         """
         The cluster information resource provides overall information about