AMBARI-16144. Stack advisor scripts should handle calls where dependent services do not exist (smohanty)

ambari-server/src/main/resources/stacks/HDP/2.0.6/services/stack_advisor.py

@@ -624,11 +624,14 @@ class HDP206StackAdvisor(DefaultStackAdvisor):
     # If no local DN in distributed mode
     if operatingMode == "distributed":
       dn_hosts = self.getComponentHostNames(services, "HDFS", "DATANODE")
-      if set(amsCollectorHosts).intersection(dn_hosts):
-        collector_cohosted_with_dn = "true"
-      else:
-        collector_cohosted_with_dn = "false"
-      putAmsHbaseSiteProperty("dfs.client.read.shortcircuit", collector_cohosted_with_dn)
+      # call by Kerberos wizard sends only the service being affected
+      # so it is possible for dn_hosts to be None but not amsCollectorHosts
+      if dn_hosts and len(dn_hosts) > 0:
+        if set(amsCollectorHosts).intersection(dn_hosts):
+          collector_cohosted_with_dn = "true"
+        else:
+          collector_cohosted_with_dn = "false"
+        putAmsHbaseSiteProperty("dfs.client.read.shortcircuit", collector_cohosted_with_dn)
 
     #split points
     scriptDir = os.path.dirname(os.path.abspath(__file__))

ambari-server/src/main/resources/stacks/HDP/2.3/services/stack_advisor.py

@@ -133,7 +133,12 @@ class HDP23StackAdvisor(HDP22StackAdvisor):
     return parentItems
 
   def __getHosts(self, componentsList, componentName):
-    return [component["hostnames"] for component in componentsList if component["component_name"] == componentName][0]
+    host_lists = [component["hostnames"] for component in componentsList if
+                  component["component_name"] == componentName]
+    if host_lists and len(host_lists) > 0:
+      return host_lists[0]
+    else:
+      return []
 
   def getNotPreferableOnServerComponents(self):
     parentComponents = super(HDP23StackAdvisor, self).getNotPreferableOnServerComponents()