verification: to use existing tempest

By default, Rally verification requires to do
following things:

* git clone tempest source from upstream
* setup virtualenv for this tempest
* setup testr environement with virtualenv above
* create tempest.conf for this tempest

If tempest is already installed/configured in rootfs
then force Rally to use this existing tempest.

If the option "existing_tempest_config" in /etc/rally/rally.conf
is not set then follows the default path.  If existing_tempest_config
is set to absolute path of tempest config folder (which
contains tempest "tools" amd .testr.conf) then Rally
uses this existing tempest.

Signed-off-by: Vu Tran <vu.tran@windriver.com>

diff --git a/rally/orchestrator/api.py b/rally/orchestrator/api.py
index d0cc769..644c16b 100644
--- a/rally/orchestrator/api.py
+++ b/rally/orchestrator/api.py
@@ -143,8 +143,11 @@ def verify(deploy_id, set_name, regex):
     verification = objects.Verification(deployment_uuid=deploy_id)
     verifier = tempest.Tempest(deploy_id, verification=verification)
     if not verifier.is_installed():
-        print("Tempest is not installed for specified deployment.")
-        print("Installing Tempest for deployment %s" % deploy_id)
+        if tempest.CONF.existing_tempest_config is None:
+            print("Tempest is not installed for specified deployment.")
+            print("Installing Tempest for deployment %s" % deploy_id)
+        else:
+            print("Configuring existing Tempest for deployment %s" % deploy_id)
         verifier.install()
     LOG.info("Starting verification of deployment: %s" % deploy_id)
 
diff --git a/rally/verification/verifiers/tempest/tempest.py b/rally/verification/verifiers/tempest/tempest.py
index 13a829d..428af49 100644
--- a/rally/verification/verifiers/tempest/tempest.py
+++ b/rally/verification/verifiers/tempest/tempest.py
@@ -25,9 +25,17 @@ from rally.openstack.common import jsonutils
 from rally import utils
 from rally.verification.verifiers.tempest import config
 from rally.verification.verifiers.tempest import subunit2json
+from oslo.config import cfg
 
 LOG = logging.getLogger(__name__)
 
+CONF = cfg.CONF
+CONF.register_opts([
+    cfg.StrOpt("existing_tempest_config", default=None,
+               help="Path to existing tempest config folder, this path "
+                    "should contain \"tools\" folder and .testr.conf file")
+])
+
 
 class Tempest(object):
 
@@ -41,8 +49,11 @@ class Tempest(object):
                                          "for-deployment-%s" % deploy_id)
         self.config_file = os.path.join(self.tempest_path, "tempest.conf")
         self.log_file_raw = os.path.join(self.tempest_path, "subunit.stream")
-        self.venv_wrapper = os.path.join(self.tempest_path,
+        if CONF.existing_tempest_config is None:
+            self.venv_wrapper = os.path.join(self.tempest_path,
                                          "tools/with_venv.sh")
+        else:
+            self.venv_wrapper = ""
         self.verification = verification
         self._env = None
 
@@ -62,6 +73,9 @@ class Tempest(object):
         return self._env
 
     def _install_venv(self):
+        if CONF.existing_tempest_config is not None:
+            open(os.path.join(self.tempest_path, '.venv'), 'w').close()
+            return
         if not os.path.isdir(os.path.join(self.tempest_path, '.venv')):
             LOG.info("No virtual environment found...Install the virtualenv.")
             LOG.debug("Virtual environment directory: %s" %
@@ -111,10 +125,13 @@ class Tempest(object):
     def install(self):
         if not self.is_installed():
             try:
-                if not os.path.exists(Tempest.tempest_base_path):
+                if CONF.existing_tempest_config is None and \
+				        not os.path.exists(Tempest.tempest_base_path):
                     Tempest._clone()
-
-                if not os.path.exists(self.tempest_path):
+                if CONF.existing_tempest_config is not None:
+                    shutil.copytree(CONF.existing_tempest_config,
+                                    self.tempest_path)
+                elif not os.path.exists(self.tempest_path):
                     shutil.copytree(Tempest.tempest_base_path,
                                     self.tempest_path)
                     subprocess.check_call("git checkout master; "
@@ -128,7 +145,10 @@ class Tempest(object):
                 self.uninstall()
                 raise exceptions.TempestSetupFailure("failed cmd: '%s'", e.cmd)
             else:
-                print("Tempest has been successfully installed!")
+                if CONF.existing_tempest_config is None:
+                    print("Tempest has been successfully installed!")
+                else:
+                    print("Verifier has been successfully configured to use existing Tempest")
 
         else:
             print("Tempest is already installed")
@@ -139,7 +159,7 @@ class Tempest(object):
 
     @utils.log_verification_wrapper(LOG.info, _("Run verification."))
     def _prepare_and_run(self, set_name, regex):
-        if not self.is_configured():
+        if CONF.existing_tempest_config is None and not self.is_configured():
             self.generate_config_file()
 
         if set_name == "full":