server: add duplicate host check

Fixes #13080

Signed-off-by: Abhishek Kumar <abhishek.mrt22@gmail.com>

Author: shwstppr

server/src/main/java/com/cloud/resource/ResourceManagerImpl.java

@@ -799,6 +799,8 @@ private List<HostVO> discoverHostsFull(final Long dcId, final Long podId, Long c
             throw new InvalidParameterValueException(url + " is not a valid uri");
         }
 
+        checkForDuplicateHost(url);
+
         final List<HostVO> hosts = new ArrayList<>();
         logger.info("Trying to add a new host at {} in data center {}", url, zone);
         boolean isHypervisorTypeSupported = false;
@@ -2609,6 +2611,24 @@ private Host createHostAndAgent(final ServerResource resource, final Map<String,
         return host;
     }
 
+    void checkForDuplicateHost(final String url) {
+        String hostIpOrName = null;
+        try {
+            hostIpOrName = new URI(UriUtils.encodeURIComponent(url)).getHost();
+        } catch (final URISyntaxException ignore) {
+            // unparseable URL - discoverer will reject it shortly anyway
+        }
+        if (StringUtils.isBlank(hostIpOrName)) {
+            return;
+        }
+        final HostVO existingByIp = _hostDao.findByIp(hostIpOrName);
+        if (existingByIp != null) {
+            throw new InvalidParameterValueException(String.format(
+                    "A host with IP address / hostname '%s' already exists (id: %s). Remove it before adding again.",
+                    hostIpOrName, existingByIp.getUuid()));
+        }
+    }
+
     private Host createHostAndAgentDeferred(final ServerResource resource, final Map<String, String> details, final boolean old, final List<String> hostTags, final boolean forRebalance) {
         HostVO host = null;
         StartupCommand[] cmds = null;

server/src/test/java/com/cloud/resource/ResourceManagerImplTest.java

@@ -219,6 +219,19 @@ public void tearDown() throws Exception {
         closeable.close();
     }
 
+    @Test(expected = InvalidParameterValueException.class)
+    public void testCheckForDuplicateHostThrowsWhenIpAlreadyExists() {
+        when(hostDao.findByIp("10.0.0.10")).thenReturn(host);
+        resourceManager.checkForDuplicateHost("http://10.0.0.10");
+    }
+
+    @Test
+    public void testCheckForDuplicateHostAllowsUniqueHost() {
+        when(hostDao.findByIp("10.0.0.30")).thenReturn(null);
+        resourceManager.checkForDuplicateHost("http://10.0.0.30");
+        verify(hostDao, times(1)).findByIp("10.0.0.30");
+    }
+
     @Test
     public void testCheckAndMaintainEnterMaintenanceModeNoVms() throws NoTransitionException {
         // Test entering into maintenance with no VMs running on host.