Read environment variables in Constants.py

Instead of using EnsureGlobalVariable,
which is clunky to use from Python.

As a consequence, all caps variables from Constants.py are used directly
and tests/__init__.robot and robot_enhancements.robot are deleted.

+ Rename the CRC global kill switch based on ci-man review.

Change-Id: I10723792475bc83352bf8c3b7f7946ecf885a194
Signed-off-by: Vratko Polak <vrpolak@cisco.com>

3 files changed, 121 insertions, 18 deletions

diff --git a/resources/libraries/python/Constants.py b/resources/libraries/python/Constants.py
index e8209544e8..9606a10fad 100644
--- a/resources/libraries/python/Constants.py
+++ b/resources/libraries/python/Constants.py
@@ -11,7 +11,112 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-"""Constants used in CSIT."""
+"""Constants used in CSIT.
+
+Here, "constant" means a value that keeps its value since initialization.
+However, the value does not need to be hardcoded here,
+some values are affected by environment variables.
+
+TODO: Review env and constant names, make them matching if possible.
+"""
+
+
+import os
+
+
+def get_str_from_env(env_var_names, default_value):
+    """Attempt to read string from environment variable, return that or default.
+
+    If environment variable exists, but is empty (and default is not),
+    empty string is returned.
+
+    Several environment variable names are examined, as CSIT currently supports
+    a mix of naming convensions.
+    Here "several" means there are hardcoded prefixes to try,
+    and env_var_names itself can be single name, or a list or a tuple of names.
+
+    :param env_var_names: Base names of environment variable to attempt to read.
+    :param default_value: Value to return if the env var does not exist.
+    :type env_var_names: str, or list of str, or tuple of str
+    :type default_value: str
+    :returns: The value read, or default value.
+    :rtype: str
+    """
+    prefixes = ("FDIO_CSIT_", "CSIT_", "")
+    if not isinstance(env_var_names, (list, tuple)):
+        env_var_names = [env_var_names]
+    for name in env_var_names:
+        for prefix in prefixes:
+            value = os.environ.get(prefix + name, None)
+            if value is not None:
+                return value
+    return default_value
+
+
+def get_int_from_env(env_var_names, default_value):
+    """Attempt to read int from environment variable, return that or default.
+
+    String value is read, default is returned also if conversion fails.
+
+    :param env_var_names: Base names of environment variable to attempt to read.
+    :param default_value: Value to return if read or conversion fails.
+    :type env_var_names: str, or list of str, or tuple of str
+    :type default_value: int
+    :returns: The value read, or default value.
+    :rtype: int
+    """
+    env_str = get_str_from_env(env_var_names, "")
+    try:
+        return int(env_str)
+    except ValueError:
+        return default_value
+
+
+def get_float_from_env(env_var_names, default_value):
+    """Attempt to read float from environment variable, return that or default.
+
+    String value is read, default is returned also if conversion fails.
+
+    :param env_var_names: Base names of environment variable to attempt to read.
+    :param default_value: Value to return if read or conversion fails.
+    :type env_var_names: str, or list of str, or tuple of str
+    :type default_value: float
+    :returns: The value read, or default value.
+    :rtype: float
+    """
+    env_str = get_str_from_env(env_var_names, "")
+    try:
+        return float(env_str)
+    except ValueError:
+        return default_value
+
+
+def get_pessimistic_bool_from_env(env_var_names):
+    """Attempt to read bool from environment variable, assume False by default.
+
+    Conversion is lenient and pessimistic, only few strings are considered true.
+
+    :param env_var_names: Base names of environment variable to attempt to read.
+    :type env_var_names: str, or list of str, or tuple of str
+    :returns: The value read, or False.
+    :rtype: bool
+    """
+    env_str = get_str_from_env(env_var_names, "").lower()
+    return True if env_str in ("true", "yes", "y", "1") else False
+
+
+def get_optimistic_bool_from_env(env_var_names):
+    """Attempt to read bool from environment variable, assume True by default.
+
+    Conversion is lenient and optimistic, only few strings are considered false.
+
+    :param env_var_names: Base names of environment variable to attempt to read.
+    :type env_var_names: str, or list of str, or tuple of str
+    :returns: The value read, or True.
+    :rtype: bool
+    """
+    env_str = get_str_from_env(env_var_names, "").lower()
+    return False if env_str in ("false", "no", "n", "0") else True
 
 
 class Constants(object):
@@ -112,8 +217,19 @@ class Constants(object):
     # Default path to VPP API socket.
     SOCKSVR_PATH = "/run/vpp/api.sock"
 
+    # Number of trials to execute in MRR test.
+    PERF_TRIAL_MULTIPLICITY = get_int_from_env("PERF_TRIAL_MULTIPLICITY", 10)
+
+    # Duration of one trial in MRR test.
+    PERF_TRIAL_DURATION = get_float_from_env("PERF_TRIAL_DURATION", 1.0)
+
+    # UUID string of DUT1 /tmp volume created outside of the
+    # DUT1 docker in case of vpp-device test. ${EMPTY} value means that
+    #  /tmp directory is inside the DUT1 docker.
+    DUT1_UUID = get_str_from_env("DUT1_UUID", "")
+
     # Global "kill switch" for CRC checking during runtime.
-    CRC_MISMATCH_FAILS_TEST = True
+    FAIL_ON_CRC_MISMATCH = get_optimistic_bool_from_env("FAIL_ON_CRC_MISMATCH")
 
     # Mapping from NIC name to its bps limit.
     # TODO: Implement logic to lower limits to TG NIC or software. Or PCI.
diff --git a/resources/libraries/python/PapiExecutor.py b/resources/libraries/python/PapiExecutor.py
index 0a714c182c..74ff7a0f9b 100644
--- a/resources/libraries/python/PapiExecutor.py
+++ b/resources/libraries/python/PapiExecutor.py
@@ -166,18 +166,6 @@ class PapiSocketExecutor(object):
         if self.vpp_instance:
             return
         cls = self.__class__  # Shorthand for setting class fields.
-        fail_on_mismatch = Constants.CRC_MISMATCH_FAILS_TEST
-        try:
-            from robot.libraries.BuiltIn import BuiltIn
-            from_robot = BuiltIn().get_variable_value(
-                "\${crc_mismatch_fails}", None)
-            if from_robot is not None:
-                # Robot interprets env vars as strings.
-                fail_on_mismatch = not from_robot.lower() in ("false", "n", "0")
-        except (ImportError, AttributeError):
-            # If robot is not installed or not running, or value is not string,
-            # the Constants value applies.
-            pass
         package_path = None
         tmp_dir = tempfile.mkdtemp(dir="/tmp")
         try:
@@ -199,8 +187,7 @@ class PapiSocketExecutor(object):
             api_json_directory = tmp_dir + "/usr/share/vpp/api"
             # Perform initial checks before .api.json files are gone,
             # by creating the checker instance.
-            cls.crc_checker = VppApiCrcChecker(
-                api_json_directory, fail_on_mismatch=fail_on_mismatch)
+            cls.crc_checker = VppApiCrcChecker(api_json_directory)
             # When present locally, we finally can find the installation path.
             package_path = glob.glob(tmp_dir + installed_papi_glob)[0]
             # Package path has to be one level above the vpp_papi directory.
diff --git a/resources/libraries/python/VppApiCrc.py b/resources/libraries/python/VppApiCrc.py
index d66d4d7568..cb6f5b0c60 100644
--- a/resources/libraries/python/VppApiCrc.py
+++ b/resources/libraries/python/VppApiCrc.py
@@ -43,8 +43,8 @@ class VppApiCrcChecker(object):
     so make sure the calling libraries have appropriate robot library scope.
     For usual testing, it means "GLOBAL" scope."""
 
-    def __init__(self, directory,
-                 fail_on_mismatch=Constants.CRC_MISMATCH_FAILS_TEST):
+    def __init__(
+            self, directory, fail_on_mismatch=Constants.FAIL_ON_CRC_MISMATCH):
         """Initialize empty state, then register known collections.
 
         This also scans directory for .api.json files