feat(web): application-level pings

6 files changed, 150 insertions, 7 deletions

diff --git a/language-web/src/main/java/tools/refinery/language/web/xtext/server/PongResult.java b/language-web/src/main/java/tools/refinery/language/web/xtext/server/PongResult.java
new file mode 100644
index 00000000..fe510f51
--- /dev/null
+++ b/language-web/src/main/java/tools/refinery/language/web/xtext/server/PongResult.java
@@ -0,0 +1,44 @@
+package tools.refinery.language.web.xtext.server;
+
+import java.util.Objects;
+
+import org.eclipse.xtext.web.server.IServiceResult;
+
+public class PongResult implements IServiceResult {
+        private String pong;
+
+        public PongResult(String pong) {
+                super();
+                this.pong = pong;
+        }
+
+        public String getPong() {
+                return pong;
+        }
+
+        public void setPong(String pong) {
+                this.pong = pong;
+        }
+
+        @Override
+        public int hashCode() {
+                return Objects.hash(pong);
+        }
+
+        @Override
+        public boolean equals(Object obj) {
+                if (this == obj)
+                        return true;
+                if (obj == null)
+                        return false;
+                if (getClass() != obj.getClass())
+                        return false;
+                PongResult other = (PongResult) obj;
+                return Objects.equals(pong, other.pong);
+        }
+
+        @Override
+        public String toString() {
+                return "PongResult [pong=" + pong + "]";
+        }
+}
diff --git a/language-web/src/main/java/tools/refinery/language/web/xtext/server/TransactionExecutor.java b/language-web/src/main/java/tools/refinery/language/web/xtext/server/TransactionExecutor.java
index f2f26d98..335f0636 100644
--- a/language-web/src/main/java/tools/refinery/language/web/xtext/server/TransactionExecutor.java
+++ b/language-web/src/main/java/tools/refinery/language/web/xtext/server/TransactionExecutor.java
@@ -46,6 +46,11 @@ public class TransactionExecutor implements IDisposable, PrecomputationListener
 
         public void handleRequest(XtextWebRequest request) throws ResponseHandlerException {
                 var serviceContext = new SimpleServiceContext(session, request.getRequestData());
+                var ping = serviceContext.getParameter("ping");
+                if (ping != null) {
+                        responseHandler.onResponse(new XtextWebOkResponse(request, new PongResult(ping)));
+                        return;
+                }
                 try {
                         var injector = getInjector(serviceContext);
                         var serviceDispatcher = injector.getInstance(XtextServiceDispatcher.class);
diff --git a/language-web/src/main/java/tools/refinery/language/web/xtext/servlet/XtextWebSocketServlet.java b/language-web/src/main/java/tools/refinery/language/web/xtext/servlet/XtextWebSocketServlet.java
index 6d4d2cad..942ca380 100644
--- a/language-web/src/main/java/tools/refinery/language/web/xtext/servlet/XtextWebSocketServlet.java
+++ b/language-web/src/main/java/tools/refinery/language/web/xtext/servlet/XtextWebSocketServlet.java
@@ -31,7 +31,7 @@ public abstract class XtextWebSocketServlet extends JettyWebSocketServlet implem
          */
         private static final long MAX_FRAME_SIZE = 4L * 1024L * 1024L;
 
-        private static final Duration IDLE_TIMEOUT = Duration.ofMinutes(10);
+        private static final Duration IDLE_TIMEOUT = Duration.ofSeconds(30);
 
         private transient Logger log = LoggerFactory.getLogger(getClass());
 
diff --git a/language-web/src/main/js/editor/XtextClient.ts b/language-web/src/main/js/editor/XtextClient.ts
index eeb67d72..27ef4165 100644
--- a/language-web/src/main/js/editor/XtextClient.ts
+++ b/language-web/src/main/js/editor/XtextClient.ts
@@ -2,7 +2,6 @@ import { Diagnostic, setDiagnostics } from '@codemirror/lint';
 import {
   ChangeDesc,
   ChangeSet,
-  EditorState,
   Transaction,
 } from '@codemirror/state';
 import { nanoid } from 'nanoid';
@@ -63,6 +62,7 @@ export class XtextClient {
   onTransaction(transaction: Transaction): void {
     const { changes } = transaction;
     if (!changes.empty) {
+      this.webSocketClient.ensureOpen();
       this.dirtyChanges = this.dirtyChanges.composeDesc(changes.desc);
       this.scheduleUpdate();
     }
diff --git a/language-web/src/main/js/editor/XtextWebSocketClient.ts b/language-web/src/main/js/editor/XtextWebSocketClient.ts
index 131e0067..f930160a 100644
--- a/language-web/src/main/js/editor/XtextWebSocketClient.ts
+++ b/language-web/src/main/js/editor/XtextWebSocketClient.ts
@@ -1,3 +1,5 @@
+import { nanoid } from 'nanoid';
+
 import { getLogger } from '../logging';
 import { PendingRequest } from './PendingRequest';
 import {
@@ -6,6 +8,7 @@ import {
   isPushMessage,
   IXtextWebRequest,
 } from './xtextMessages';
+import { isPongResult } from './xtextServiceResults';
 
 const XTEXT_SUBPROTOCOL_V1 = 'tools.refinery.language.web.xtext.v1';
 
@@ -13,6 +16,10 @@ const WEBSOCKET_CLOSE_OK = 1000;
 
 const RECONNECT_DELAY_MS = 1000;
 
+const IDLE_TIMEOUT_MS = 10 * 60 * 1000;
+
+const PING_TIMEOUT_MS = 10 * 1000;
+
 const log = getLogger('XtextWebSocketClient');
 
 type ReconnectHandler = () => void;
@@ -34,6 +41,10 @@ export class XtextWebSocketClient {
 
   reconnectTimeout: NodeJS.Timeout | null = null;
 
+  idleTimeout: NodeJS.Timeout | null = null;
+
+  pingTimeout: NodeJS.Timeout | null = null;
+
   constructor(onReconnect: ReconnectHandler, onPush: PushHandler) {
     this.onReconnect = onReconnect;
     this.onPush = onPush;
@@ -44,6 +55,18 @@ export class XtextWebSocketClient {
     return this.connection.readyState === WebSocket.OPEN;
   }
 
+  get isClosed(): boolean {
+    return this.connection.readyState === WebSocket.CLOSING
+      || this.connection.readyState === WebSocket.CLOSED;
+  }
+
+  ensureOpen(): void {
+    if (this.isClosed) {
+      this.closing = false;
+      this.reconnect();
+    }
+  }
+
   private reconnect() {
     this.reconnectTimeout = null;
     const webSocketServer = window.origin.replace(/^http/, 'ws');
@@ -71,18 +94,75 @@ export class XtextWebSocketClient {
       }
       this.cleanupAndMaybeReconnect();
     });
+    this.scheduleIdleTimeout();
+    this.schedulePingTimeout();
+  }
+
+  private scheduleIdleTimeout() {
+    if (this.idleTimeout !== null) {
+      clearTimeout(this.idleTimeout);
+    }
+    this.idleTimeout = setTimeout(() => {
+      log.info('Closing websocket connection due to inactivity');
+      this.close();
+    }, IDLE_TIMEOUT_MS);
+  }
+
+  private schedulePingTimeout() {
+    if (this.pingTimeout !== null) {
+      return;
+    }
+    this.pingTimeout = setTimeout(() => {
+      if (this.isClosed) {
+        return;
+      }
+      if (this.isOpen) {
+        const ping = nanoid();
+        log.trace('ping:', ping);
+        this.pingTimeout = null;
+        this.internalSend({
+          ping,
+        }).catch((error) => {
+          log.error('ping error', error);
+          this.forceReconnectDueToError();
+        }).then((result) => {
+          if (!isPongResult(result) || result.pong !== ping) {
+            log.error('invalid pong');
+            this.forceReconnectDueToError();
+          }
+          log.trace('pong:', ping);
+        });
+      }
+      this.schedulePingTimeout();
+    }, PING_TIMEOUT_MS);
   }
 
   private cleanupAndMaybeReconnect() {
+    this.cleanup();
+    if (!this.closing) {
+      this.delayedReconnect();
+    }
+  }
+
+  private cleanup() {
     this.pendingRequests.forEach((pendingRequest) => {
       pendingRequest.reject(new Error('Websocket closed'));
     });
     this.pendingRequests.clear();
-    if (this.closing) {
-      return;
+    if (this.idleTimeout !== null) {
+      clearTimeout(this.idleTimeout);
+      this.idleTimeout = null;
     }
+    if (this.pingTimeout !== null) {
+      clearTimeout(this.pingTimeout);
+      this.pingTimeout = null;
+    }
+  }
+
+  private delayedReconnect() {
     if (this.reconnectTimeout !== null) {
       clearTimeout(this.reconnectTimeout);
+      this.reconnectTimeout = null;
     }
     this.reconnectTimeout = setTimeout(() => {
       log.info('Attempting to reconnect websocket');
@@ -99,6 +179,11 @@ export class XtextWebSocketClient {
     if (!this.isOpen) {
       throw new Error('Connection is not open');
     }
+    this.scheduleIdleTimeout();
+    return this.internalSend(request);
+  }
+
+  private internalSend(request: unknown): Promise<unknown> {
     const messageId = this.nextMessageId.toString(16);
     if (messageId in this.pendingRequests) {
       log.error('Message id wraparound still pending', messageId);
@@ -171,15 +256,15 @@ export class XtextWebSocketClient {
   }
 
   private closeConnection() {
-    if (this.connection && this.connection.readyState !== WebSocket.CLOSING
-      && this.connection.readyState !== WebSocket.CLOSED) {
+    if (!this.isClosed) {
       log.info('Closing websocket connection');
-      this.connection.close();
+      this.connection.close(1000, 'end session');
     }
   }
 
   close(): void {
     this.closing = true;
     this.closeConnection();
+    this.cleanup();
   }
 }
diff --git a/language-web/src/main/js/editor/xtextServiceResults.ts b/language-web/src/main/js/editor/xtextServiceResults.ts
index 2a66566a..8fa7a321 100644
--- a/language-web/src/main/js/editor/xtextServiceResults.ts
+++ b/language-web/src/main/js/editor/xtextServiceResults.ts
@@ -1,3 +1,12 @@
+export interface IPongResult {
+  pong: string;
+}
+
+export function isPongResult(result: unknown): result is IPongResult {
+  const pongResult = result as IPongResult;
+  return typeof pongResult.pong === 'string';
+}
+
 export interface IDocumentStateResult {
   stateId: string;
 }