Re-factor Node.py to use better python inbuilt functions

1. don't use sys.exit() to exit when there is an exception, it will hide
the underlying error
2. use the Abstract Base Classes for type checking.
3. don't have to build list, can use next

JIRA: YARDSTICK-541

Change-Id: Id4485acb21e7e02bbc22d3e689cbf0699363098a
Signed-off-by: Deepak S <deepak.s@linux.intel.com>

2 files changed, 37 insertions, 23 deletions

diff --git a/tests/unit/benchmark/contexts/test_node.py b/tests/unit/benchmark/contexts/test_node.py
index de5ba7066..64fe4a566 100644
--- a/tests/unit/benchmark/contexts/test_node.py
+++ b/tests/unit/benchmark/contexts/test_node.py
@@ -42,7 +42,7 @@ class NodeContextTestCase(unittest.TestCase):
             'file': self._get_file_abspath("error_file")
         }
 
-        self.assertRaises(SystemExit, self.test_context.init, attrs)
+        self.assertRaises(IOError, self.test_context.init, attrs)
 
     def test_successful_init(self):
 
@@ -100,7 +100,7 @@ class NodeContextTestCase(unittest.TestCase):
 
         attr_name = 'node1.foo'
 
-        self.assertRaises(SystemExit, self.test_context._get_server, attr_name)
+        self.assertRaises(ValueError, self.test_context._get_server, attr_name)
 
     def test__get_server_found(self):
 
diff --git a/yardstick/benchmark/contexts/node.py b/yardstick/benchmark/contexts/node.py
index e02a71669..9242e2727 100644
--- a/yardstick/benchmark/contexts/node.py
+++ b/yardstick/benchmark/contexts/node.py
@@ -8,10 +8,11 @@
 ##############################################################################
 
 from __future__ import absolute_import
-import sys
+import logging
+import errno
 import os
+import collections
 import yaml
-import logging
 
 from yardstick.benchmark.contexts.base import Context
 from yardstick.definitions import YARDSTICK_ROOT_PATH
@@ -33,20 +34,28 @@ class NodeContext(Context):
         self.baremetals = []
         super(self.__class__, self).__init__()
 
+    def read_config_file(self):
+        """Read from config file"""
+
+        with open(self.file_path) as stream:
+            LOG.info("Parsing pod file: %s", self.file_path)
+            cfg = yaml.load(stream)
+        return cfg
+
     def init(self, attrs):
         """initializes itself from the supplied arguments"""
         self.name = attrs["name"]
         self.file_path = attrs.get("file", "pod.yaml")
-        if not os.path.exists(self.file_path):
-            self.file_path = os.path.join(YARDSTICK_ROOT_PATH, self.file_path)
-
-        LOG.info("Parsing pod file: %s", self.file_path)
 
         try:
-            with open(self.file_path) as stream:
-                cfg = yaml.load(stream)
+            cfg = self.read_config_file()
         except IOError as ioerror:
-            sys.exit(ioerror)
+            if ioerror.errno == errno.ENOENT:
+                self.file_path = \
+                    os.path.join(YARDSTICK_ROOT_PATH, self.file_path)
+                cfg = self.read_config_file()
+            else:
+                raise
 
         self.nodes.extend(cfg["nodes"])
         self.controllers.extend([node for node in cfg["nodes"]
@@ -72,23 +81,28 @@ class NodeContext(Context):
         """lookup server info by name from context
         attr_name: a name for a server listed in nodes config file
         """
-        if type(attr_name) is dict:
+        if isinstance(attr_name, collections.Mapping):
             return None
 
         if self.name != attr_name.split(".")[1]:
             return None
         node_name = attr_name.split(".")[0]
-        nodes = [n for n in self.nodes
-                 if n["name"] == node_name]
-        if len(nodes) == 0:
+        matching_nodes = (n for n in self.nodes if n["name"] == node_name)
+
+        try:
+            # A clone is created in order to avoid affecting the
+            # original one.
+            node = dict(next(matching_nodes))
+        except StopIteration:
             return None
-        elif len(nodes) > 1:
-            LOG.error("Duplicate nodes!!!")
-            LOG.error("Nodes: %r", nodes)
-            sys.exit(-1)
-
-        # A clone is created in order to avoid affecting the
-        # original one.
-        node = dict(nodes[0])
+
+        try:
+            duplicate = next(matching_nodes)
+        except StopIteration:
+            pass
+        else:
+            raise ValueError("Duplicate nodes!!! Nodes: %s %s",
+                             (matching_nodes, duplicate))
+
         node["name"] = attr_name
         return node