CORDA-1686: Make Node Explorer release its RPC connection on shutdown. (#3457)

* Make Node Explorer release its RPC connection on shutdown.
* Declare Explorer's login() function as tail-recursive.
* Replace lateinit rpcConnection with oridinary var.
* Notify the node when closing an RPC connection gracefully.

client/jfx/src/main/kotlin/net/corda/client/jfx/model/NodeMonitorModel.kt

@@ -40,7 +40,7 @@ data class ProgressTrackingEvent(val stateMachineId: StateMachineRunId, val mess
 /**
  * This model exposes raw event streams to and from the node.
  */
-class NodeMonitorModel {
+class NodeMonitorModel : AutoCloseable {
 
     private val retryableStateMachineUpdatesSubject = PublishSubject.create<StateMachineUpdate>()
     private val stateMachineUpdatesSubject = PublishSubject.create<StateMachineUpdate>()
@@ -49,6 +49,7 @@ class NodeMonitorModel {
     private val stateMachineTransactionMappingSubject = PublishSubject.create<StateMachineTransactionMapping>()
     private val progressTrackingSubject = PublishSubject.create<ProgressTrackingEvent>()
     private val networkMapSubject = PublishSubject.create<MapChange>()
+    private var rpcConnection: CordaRPCConnection? = null
 
     val stateMachineUpdates: Observable<StateMachineUpdate> = stateMachineUpdatesSubject
     val vaultUpdates: Observable<Vault.Update<ContractState>> = vaultUpdatesSubject
@@ -84,6 +85,17 @@ class NodeMonitorModel {
      */
     class CordaRPCOpsWrapper(val cordaRPCOps: CordaRPCOps)
 
+    /**
+     * Disconnects from the Corda node for a clean client shutdown.
+     */
+    override fun close() {
+        try {
+            rpcConnection?.notifyServerAndClose()
+        } catch (e: Exception) {
+            logger.error("Error closing RPC connection to node", e)
+        }
+    }
+
     /**
      * Register for updates to/from a given vault.
      * TODO provide an unsubscribe mechanism
@@ -145,9 +157,10 @@ class NodeMonitorModel {
     }
 
     private fun performRpcReconnect(nodeHostAndPort: NetworkHostAndPort, username: String, password: String, shouldRetry: Boolean): List<StateMachineInfo> {
-
-        val connection = establishConnectionWithRetry(nodeHostAndPort, username, password, shouldRetry)
-        val proxy = connection.proxy
+        val proxy = establishConnectionWithRetry(nodeHostAndPort, username, password, shouldRetry).let { connection ->
+            rpcConnection = connection
+            connection.proxy
+        }
 
         val (stateMachineInfos, stateMachineUpdatesRaw) = proxy.stateMachinesFeed()
 
@@ -162,7 +175,7 @@ class NodeMonitorModel {
                     // It is good idea to close connection to properly mark the end of it. During re-connect we will create a new
                     // client and a new connection, so no going back to this one. Also the server might be down, so we are
                     // force closing the connection to avoid propagation of notification to the server side.
-                    connection.forceClose()
+                    rpcConnection?.forceClose()
                     // Perform re-connect.
                     performRpcReconnect(nodeHostAndPort, username, password, shouldRetry = true)
                 })
@@ -175,18 +188,17 @@ class NodeMonitorModel {
     }
 
     private fun establishConnectionWithRetry(nodeHostAndPort: NetworkHostAndPort, username: String, password: String, shouldRetry: Boolean): CordaRPCConnection {
-
         val retryInterval = 5.seconds
 
+        val client = CordaRPCClient(
+            nodeHostAndPort,
+            CordaRPCClientConfiguration.DEFAULT.copy(
+                connectionMaxRetryInterval = retryInterval
+            )
+        )
         do {
             val connection = try {
                 logger.info("Connecting to: $nodeHostAndPort")
-                val client = CordaRPCClient(
-                        nodeHostAndPort,
-                        CordaRPCClientConfiguration.DEFAULT.copy(
-                                connectionMaxRetryInterval = retryInterval
-                        )
-                )
                 val _connection = client.start(username, password)
                 // Check connection is truly operational before returning it.
                 val nodeInfo = _connection.proxy.nodeInfo()
@@ -195,7 +207,7 @@ class NodeMonitorModel {
             } catch (throwable: Throwable) {
                 if (shouldRetry) {
                     // Deliberately not logging full stack trace as it will be full of internal stacktraces.
-                    logger.info("Exception upon establishing connection: " + throwable.message)
+                    logger.info("Exception upon establishing connection: {}", throwable.message)
                     null
                 } else {
                     throw throwable

tools/explorer/src/main/kotlin/net/corda/explorer/Main.kt

@@ -10,6 +10,7 @@ import javafx.stage.Stage
 import jfxtras.resources.JFXtrasFontRoboto
 import joptsimple.OptionParser
 import net.corda.client.jfx.model.Models
+import net.corda.client.jfx.model.NodeMonitorModel
 import net.corda.client.jfx.model.observableValue
 import net.corda.core.utilities.contextLogger
 import net.corda.explorer.model.CordaViewModel
@@ -21,6 +22,7 @@ import org.controlsfx.dialog.ExceptionDialog
 import tornadofx.App
 import tornadofx.addStageIcon
 import tornadofx.find
+import kotlin.system.exitProcess
 
 /**
  * Main class for Explorer, you will need Tornado FX to run the explorer.
@@ -34,6 +36,8 @@ class Main : App(MainView::class) {
     }
 
     override fun start(stage: Stage) {
+        var nodeModel: NodeMonitorModel? = null
+
         // Login to Corda node
         super.start(stage)
         stage.minHeight = 600.0
@@ -43,27 +47,29 @@ class Main : App(MainView::class) {
             val button = Alert(Alert.AlertType.CONFIRMATION, "Are you sure you want to exit Corda explorer?").apply {
                 initOwner(stage.scene.window)
             }.showAndWait().get()
-            if (button != ButtonType.OK) it.consume()
+            if (button == ButtonType.OK) {
+                nodeModel?.close()
+            } else {
+                it.consume()
+            }
         }
 
         val hostname = parameters.named["host"]
         val port = asInteger(parameters.named["port"])
         val username = parameters.named["username"]
         val password = parameters.named["password"]
-        var isLoggedIn = false
 
         if ((hostname != null) && (port != null) && (username != null) && (password != null)) {
             try {
-                loginView.login(hostname, port, username, password)
-                isLoggedIn = true
+                nodeModel = loginView.login(hostname, port, username, password)
             } catch (e: Exception) {
                 ExceptionDialog(e).apply { initOwner(stage.scene.window) }.showAndWait()
             }
         }
 
-        if (!isLoggedIn) {
+        if (nodeModel == null) {
             stage.hide()
-            loginView.login()
+            nodeModel = loginView.login()
             stage.show()
         }
     }
@@ -84,7 +90,7 @@ class Main : App(MainView::class) {
             runInFxApplicationThread {
                 // [showAndWait] need to be in the FX thread.
                 ExceptionDialog(throwable).showAndWait()
-                System.exit(1)
+                exitProcess(1)
             }
         }
         // Do this first before creating the notification bar, so it can autosize itself properly.

tools/explorer/src/main/kotlin/net/corda/explorer/views/LoginView.kt

@@ -27,11 +27,14 @@ class LoginView : View(WINDOW_TITLE) {
     private val port by objectProperty(SettingsModel::portProperty)
     private val fullscreen by objectProperty(SettingsModel::fullscreenProperty)
 
-    fun login(host: String, port: Int, username: String, password: String) {
-        getModel<NodeMonitorModel>().register(NetworkHostAndPort(host, port), username, password)
+    fun login(host: String, port: Int, username: String, password: String): NodeMonitorModel {
+        return getModel<NodeMonitorModel>().apply {
+            register(NetworkHostAndPort(host, port), username, password)
+        }
     }
 
-    fun login() {
+    tailrec fun login(): NodeMonitorModel? {
+        var nodeModel: NodeMonitorModel? = null
         val status = Dialog<LoginStatus>().apply {
             dialogPane = root
             setResultConverter {
@@ -39,7 +42,7 @@ class LoginView : View(WINDOW_TITLE) {
                     ButtonBar.ButtonData.OK_DONE -> try {
                         root.isDisable = true
                         // TODO : Run this async to avoid UI lockup.
-                        login(hostTextField.text, portProperty.value, usernameTextField.text, passwordTextField.text)
+                        nodeModel = login(hostTextField.text, portProperty.value, usernameTextField.text, passwordTextField.text)
                         if (!rememberMe.value) {
                             username.value = ""
                             host.value = ""
@@ -64,12 +67,13 @@ class LoginView : View(WINDOW_TITLE) {
                         initOwner(root.scene.window)
                     }.showAndWait().get()
                     if (button == ButtonType.OK) {
+                        nodeModel?.close()
                         exitProcess(0)
                     }
                 }
             }
         }.showAndWait().get()
-        if (status != LoginStatus.loggedIn) login()
+        return if (status == LoginStatus.loggedIn) nodeModel else login()
     }
 
     init {