--- a/storage/core/src/main/java/com/redhat/thermostat/storage/dao/HostInfoDAO.java	Wed Jul 31 18:58:17 2013 -0400
+++ b/storage/core/src/main/java/com/redhat/thermostat/storage/dao/HostInfoDAO.java	Wed Jul 31 15:36:00 2013 +0200
@@ -59,11 +59,26 @@
             Key.AGENT_ID, hostNameKey, osNameKey, osKernelKey,
             cpuCountKey, cpuModelKey, hostMemoryTotalKey);
 
+    /**
+     * 
+     * @param ref The host ref for which to get the HostInfo object for.
+     * @return The corresponding HostInfo object. May return null if the user
+     *         is not permitted to retrieve this HostInfo.
+     */
     HostInfo getHostInfo(HostRef ref);
 
     void putHostInfo(HostInfo info);
 
+    /**
+     * 
+     * @return A collection of hosts, which may be empty.
+     */
     Collection<HostRef> getHosts();
+    
+    /**
+     * 
+     * @return A collection of alive hosts which may be empty.
+     */
     Collection<HostRef> getAliveHosts();
 }
 

--- a/storage/core/src/main/java/com/redhat/thermostat/storage/internal/dao/HostInfoDAOImpl.java	Wed Jul 31 18:58:17 2013 -0400
+++ b/storage/core/src/main/java/com/redhat/thermostat/storage/internal/dao/HostInfoDAOImpl.java	Wed Jul 31 15:36:00 2013 +0200
@@ -145,7 +145,11 @@
         List<AgentInformation> agentInfos = agentInfoDao.getAliveAgents();
         for (AgentInformation agentInfo : agentInfos) {
             HostInfo hostInfo = getHostInfo(agentInfo.getAgentId());
-            hosts.add(toHostRef(hostInfo));
+            // getHostInfo may return null if user is not allowed to
+            // see the given host by ACL.
+            if (hostInfo != null) {
+                hosts.add(toHostRef(hostInfo));
+            }
         }
 
         return hosts;

--- a/storage/core/src/test/java/com/redhat/thermostat/storage/internal/dao/HostInfoDAOTest.java	Wed Jul 31 18:58:17 2013 -0400
+++ b/storage/core/src/test/java/com/redhat/thermostat/storage/internal/dao/HostInfoDAOTest.java	Wed Jul 31 15:36:00 2013 +0200
@@ -251,14 +251,26 @@
         verify(stmt).executeQuery();
     }
     
+    @Test
+    public void getAliveHostsEmptyDueToHostInfoBeingNull() throws DescriptorParsingException, StatementExecutionException {
+        Triple<Storage, AgentInfoDAO, PreparedStatement<HostInfo>> setup = setupForNullHostInfo();
+        Storage storage = setup.first;
+        AgentInfoDAO agentInfoDao = setup.second;
+        PreparedStatement<HostInfo> stmt = setup.third;
+
+        HostInfoDAO hostsDAO = new HostInfoDAOImpl(storage, agentInfoDao);
+        Collection<HostRef> hosts = hostsDAO.getAliveHosts();
+
+        assertEquals(0, hosts.size());
+        verify(storage).prepareStatement(anyDescriptor());
+        verify(stmt).setString(0, "123");
+        verify(stmt).executeQuery();
+    }
+    
     private Triple<Storage, AgentInfoDAO, PreparedStatement<HostInfo>> setupForSingleAliveHost()
             throws DescriptorParsingException, StatementExecutionException {
         
         // agents
-        
-        AgentInformation agentConfig1 = new AgentInformation();
-        agentConfig1.setAgentId("123");
-        agentConfig1.setAlive(true);
 
         AgentInformation agentInfo1 = new AgentInformation();
         agentInfo1.setAgentId("123");
@@ -294,6 +306,35 @@
 
         return new Triple<>(storage, agentDao, stmt);
     }
+    
+    private Triple<Storage, AgentInfoDAO, PreparedStatement<HostInfo>> setupForNullHostInfo()
+            throws DescriptorParsingException, StatementExecutionException {
+        
+        // agents
+
+        AgentInformation agentInfo1 = new AgentInformation();
+        agentInfo1.setAgentId("123");
+        agentInfo1.setAlive(true);
+        
+        // cursor
+
+        @SuppressWarnings("unchecked")
+        Cursor<HostInfo> cursor1 = mock(Cursor.class);
+        when(cursor1.hasNext()).thenReturn(false);
+
+        // storage
+        
+        Storage storage = mock(Storage.class);
+        @SuppressWarnings("unchecked")
+        PreparedStatement<HostInfo> stmt = (PreparedStatement<HostInfo>) mock(PreparedStatement.class);
+        when(storage.prepareStatement(anyDescriptor())).thenReturn(stmt);
+        when(stmt.executeQuery()).thenReturn(cursor1);
+
+        AgentInfoDAO agentDao = mock(AgentInfoDAO.class);
+        when(agentDao.getAliveAgents()).thenReturn(Arrays.asList(agentInfo1));
+
+        return new Triple<>(storage, agentDao, stmt);
+    }
 
     @Test
     public void getAliveHost3() throws DescriptorParsingException, StatementExecutionException {