Allow multiple simultaneous console viewers for KVM user VMs

PendingReleaseNotes

@@ -39,3 +39,8 @@ example.ver.1 > example.ver.2:
     which can now be attached to Instances. This is to prevent the Secondary
     Storage to grow to enormous sizes as Linux Distributions keep growing in
     size while a stripped down Linux should fit on a 2.88MB floppy.
+
+KVM console:
+  * Added the global setting `consoleproxy.kvm.multiple.viewers.enabled` to allow
+    multiple users to simultaneously access the console of the same KVM user VM.
+    The setting defaults to false to preserve the existing single-viewer behavior.

api/src/main/java/org/apache/cloudstack/consoleproxy/ConsoleAccessManager.java

@@ -41,6 +41,13 @@ public interface ConsoleAccessManager extends Manager, Configurable {
             false,
             ConfigKey.Scope.Global);
 
+    ConfigKey<Boolean> KvmMultipleConsoleViewersEnabled = new ConfigKey<>("Advanced", Boolean.class,
+            "consoleproxy.kvm.multiple.viewers.enabled",
+            "false",
+            "Determines whether multiple simultaneous console viewers are allowed for the same KVM user VM",
+            true,
+            ConfigKey.Scope.Global);
+
     ConsoleEndpoint generateConsoleEndpoint(Long vmId, String extraSecurityToken, String clientAddress);
 
     boolean isSessionAllowed(String sessionUuid);

server/src/main/java/org/apache/cloudstack/consoleproxy/ConsoleAccessManagerImpl.java

@@ -160,7 +160,8 @@ public String getConfigComponentName() {
     public ConfigKey<?>[] getConfigKeys() {
         return new ConfigKey[] {
                 ConsoleAccessManager.ConsoleSessionCleanupInterval,
-                ConsoleAccessManager.ConsoleSessionCleanupRetentionHours
+                ConsoleAccessManager.ConsoleSessionCleanupRetentionHours,
+                ConsoleAccessManager.KvmMultipleConsoleViewersEnabled
         };
     }
 
@@ -474,6 +475,10 @@ protected Pair<String, Integer> getHostAndPortForKVMMaintenanceHostIfNeeded(Host
         return null;
     }
 
+    protected boolean isKvmMultipleConsoleViewersEnabled() {
+        return ConsoleAccessManager.KvmMultipleConsoleViewersEnabled.value();
+    }
+
     protected ConsoleConnectionDetails getConsoleConnectionDetails(VirtualMachine vm, HostVO host) {
         String locale = null;
         String tag = vm.getUuid();
@@ -507,6 +512,13 @@ protected ConsoleConnectionDetails getConsoleConnectionDetails(VirtualMachine vm
                     .getValue()));
             logger.debug("HyperV RDP port for {} on {} is: {}", vm, host, details.getPort());
         }
+
+        if (Hypervisor.HypervisorType.KVM.equals(host.getHypervisorType()) &&
+                VirtualMachine.Type.User.equals(vm.getType()) &&
+                isKvmMultipleConsoleViewersEnabled()) {
+            details.setSessionRequiresNewViewer(true);
+        }
+
         return details;
     }
 

server/src/test/java/org/apache/cloudstack/consoleproxy/ConsoleAccessManagerImplTest.java

@@ -545,6 +545,80 @@ public void getConsoleConnectionDetailsReturnsDetailsForKVMHypervisor() {
         Assert.assertEquals(port, result.getPort());
     }
 
+    @Test
+    public void getConsoleConnectionDetailsRequiresNewViewerForKVMUserVmWhenMultipleViewersEnabled() {
+        VirtualMachine vm = Mockito.mock(VirtualMachine.class);
+        HostVO host = Mockito.mock(HostVO.class);
+        String hostAddress = "192.168.1.100";
+        int port = 5900;
+        Pair<String, Integer> hostPortInfo = new Pair<>(hostAddress, port);
+
+        Mockito.when(vm.getUuid()).thenReturn("vm-uuid");
+        Mockito.when(vm.getHostName()).thenReturn("vm-hostname");
+        Mockito.when(vm.getVncPassword()).thenReturn("vnc-password");
+        Mockito.when(vm.getType()).thenReturn(VirtualMachine.Type.User);
+        Mockito.when(host.getHypervisorType()).thenReturn(Hypervisor.HypervisorType.KVM);
+        Mockito.when(vmInstanceDetailsDao.listDetailsKeyPairs(Mockito.anyLong(), Mockito.anyList())).thenReturn(Map.of());
+        Mockito.when(managementServer.getVncPort(vm)).thenReturn(hostPortInfo);
+        Mockito.doReturn(new Ternary<>(hostAddress, null, null))
+                .when(consoleAccessManager).parseHostInfo(Mockito.anyString());
+        Mockito.doReturn(true).when(consoleAccessManager).isKvmMultipleConsoleViewersEnabled();
+
+        ConsoleConnectionDetails result = consoleAccessManager.getConsoleConnectionDetails(vm, host);
+
+        Assert.assertNotNull(result);
+        Assert.assertTrue(result.isSessionRequiresNewViewer());
+    }
+
+    @Test
+    public void getConsoleConnectionDetailsDoesNotRequireNewViewerForKVMUserVmWhenMultipleViewersDisabled() {
+        VirtualMachine vm = Mockito.mock(VirtualMachine.class);
+        HostVO host = Mockito.mock(HostVO.class);
+        String hostAddress = "192.168.1.100";
+        int port = 5900;
+        Pair<String, Integer> hostPortInfo = new Pair<>(hostAddress, port);
+
+        Mockito.when(vm.getUuid()).thenReturn("vm-uuid");
+        Mockito.when(vm.getHostName()).thenReturn("vm-hostname");
+        Mockito.when(vm.getVncPassword()).thenReturn("vnc-password");
+        Mockito.when(vm.getType()).thenReturn(VirtualMachine.Type.User);
+        Mockito.when(host.getHypervisorType()).thenReturn(Hypervisor.HypervisorType.KVM);
+        Mockito.when(vmInstanceDetailsDao.listDetailsKeyPairs(Mockito.anyLong(), Mockito.anyList())).thenReturn(Map.of());
+        Mockito.when(managementServer.getVncPort(vm)).thenReturn(hostPortInfo);
+        Mockito.doReturn(new Ternary<>(hostAddress, null, null))
+                .when(consoleAccessManager).parseHostInfo(Mockito.anyString());
+        Mockito.doReturn(false).when(consoleAccessManager).isKvmMultipleConsoleViewersEnabled();
+
+        ConsoleConnectionDetails result = consoleAccessManager.getConsoleConnectionDetails(vm, host);
+
+        Assert.assertNotNull(result);
+        Assert.assertFalse(result.isSessionRequiresNewViewer());
+    }
+
+    @Test
+    public void getConsoleConnectionDetailsDoesNotRequireNewViewerForKVMSystemVm() {
+        VirtualMachine vm = Mockito.mock(VirtualMachine.class);
+        HostVO host = Mockito.mock(HostVO.class);
+        String hostAddress = "192.168.1.100";
+        int port = 5900;
+        Pair<String, Integer> hostPortInfo = new Pair<>(hostAddress, port);
+
+        Mockito.when(vm.getUuid()).thenReturn("vm-uuid");
+        Mockito.when(vm.getHostName()).thenReturn("vm-hostname");
+        Mockito.when(vm.getVncPassword()).thenReturn("vnc-password");
+        Mockito.when(vm.getType()).thenReturn(VirtualMachine.Type.DomainRouter);
+        Mockito.when(host.getHypervisorType()).thenReturn(Hypervisor.HypervisorType.KVM);
+        Mockito.when(vmInstanceDetailsDao.listDetailsKeyPairs(Mockito.anyLong(), Mockito.anyList())).thenReturn(Map.of());
+        Mockito.when(managementServer.getVncPort(vm)).thenReturn(hostPortInfo);
+        Mockito.doReturn(new Ternary<>(hostAddress, null, null))
+                .when(consoleAccessManager).parseHostInfo(Mockito.anyString());
+        ConsoleConnectionDetails result = consoleAccessManager.getConsoleConnectionDetails(vm, host);
+
+        Assert.assertNotNull(result);
+        Assert.assertFalse(result.isSessionRequiresNewViewer());
+        Mockito.verify(consoleAccessManager, Mockito.never()).isKvmMultipleConsoleViewersEnabled();
+    }
+
     @Test
     public void getConsoleConnectionDetailsReturnsDetailsWithRDPForHyperV() {
         VirtualMachine vm = Mockito.mock(VirtualMachine.class);