Fix for getting optional information about openshift cluster version. (…

…#137)

* Fix for getting optional information about openshift cluster version.

* Rephrased comment after rebase

cerberus/invoke/command.py

@@ -3,7 +3,8 @@
 import sys
 
 
-# Invokes a given command and returns the stdout
+# Invokes a given command and returns the stdout.
+# Will stop Cerberus execution with exit code 1.
 def invoke(command):
     output = ""
     try:
@@ -13,3 +14,18 @@ def invoke(command):
         logging.error("Failed to run %s" % (command))
         sys.exit(1)
     return output
+
+
+# Invokes a given command and returns the stdout.
+# In case of exception, returns message about the impossibility to execute the command instead of stdout.
+# It won't stop Cerberus execution but doesn't guarantee that command returns expected stdout.
+def optional_invoke(command):
+    try:
+        optional_output = subprocess.check_output(command, shell=True,
+                                                  universal_newlines=True)
+    except Exception:
+        optional_output = "Result is absent."
+        logging.info(
+            "Optional command '%s' can't be executed, but it's not a problem at all. We can continue." % command)
+
+    return optional_output

start_cerberus.py

@@ -106,8 +106,12 @@ def main(cfg):
         # Cluster info
         logging.info("Fetching cluster info")
         if distribution == "openshift":
-            cluster_version = runcommand.invoke("kubectl get clusterversion")
-            logging.info("\n%s" % (cluster_version))
+            oc_version = runcommand.optional_invoke("oc version")
+            logging.info("oc version:\n%s" % oc_version)
+
+            cluster_version = runcommand.optional_invoke("oc get clusterversion")
+            logging.info("oc get clusterversion:\n%s" % cluster_version)
+
         cluster_info = runcommand.invoke("kubectl cluster-info | awk 'NR==1' | sed -r "
                                          "'s/\x1B\[([0-9]{1,3}(;[0-9]{1,2})?)?[mGK]//g'")  # noqa
         logging.info("%s" % (cluster_info))