Move EventSource to SharedWorker (#12095)

Move EventSource to use a SharedWorker. This prevents issues with HTTP/1.1
open browser connections from preventing gitea from opening multiple tabs.

Also allow setting EVENT_SOURCE_UPDATE_TIME to disable EventSource updating

Fix #11978

Signed-off-by: Andrew Thornton <art27@cantab.net>

Co-authored-by: silverwind <me@silverwind.io>
Co-authored-by: techknowlogick <techknowlogick@gitea.io>

3 files changed, 209 insertions, 30 deletions

diff --git a/web_src/js/features/eventsource.sharedworker.js b/web_src/js/features/eventsource.sharedworker.js
new file mode 100644
index 0000000000..7dccd8994e
--- /dev/null
+++ b/web_src/js/features/eventsource.sharedworker.js
@@ -0,0 +1,140 @@
+self.name = 'eventsource.sharedworker.js';
+
+const sourcesByUrl = {};
+const sourcesByPort = {};
+
+class Source {
+  constructor(url) {
+    this.url = url;
+    this.eventSource = new EventSource(url);
+    this.listening = {};
+    this.clients = [];
+    this.listen('open');
+    this.listen('logout');
+    this.listen('notification-count');
+    this.listen('error');
+  }
+
+  register(port) {
+    if (!this.clients.includes(port)) return;
+
+    this.clients.push(port);
+
+    port.postMessage({
+      type: 'status',
+      message: `registered to ${this.url}`,
+    });
+  }
+
+  deregister(port) {
+    const portIdx = this.clients.indexOf(port);
+    if (portIdx < 0) {
+      return this.clients.length;
+    }
+    this.clients.splice(portIdx, 1);
+    return this.clients.length;
+  }
+
+  close() {
+    if (!this.eventSource) return;
+
+    this.eventSource.close();
+    this.eventSource = null;
+  }
+
+  listen(eventType) {
+    if (this.listening[eventType]) return;
+    this.listening[eventType] = true;
+    const self = this;
+    this.eventSource.addEventListener(eventType, (event) => {
+      self.notifyClients({
+        type: eventType,
+        data: event.data
+      });
+    });
+  }
+
+  notifyClients(event) {
+    for (const client of this.clients) {
+      client.postMessage(event);
+    }
+  }
+
+  status(port) {
+    port.postMessage({
+      type: 'status',
+      message: `url: ${this.url} readyState: ${this.eventSource.readyState}`,
+    });
+  }
+}
+
+self.onconnect = (e) => {
+  for (const port of e.ports) {
+    port.addEventListener('message', (event) => {
+      if (event.data.type === 'start') {
+        const url = event.data.url;
+        if (sourcesByUrl[url]) {
+          // we have a Source registered to this url
+          const source = sourcesByUrl[url];
+          source.register(port);
+          sourcesByPort[port] = source;
+          return;
+        }
+        let source = sourcesByPort[port];
+        if (source) {
+          if (source.eventSource && source.url === url) return;
+
+          // How this has happened I don't understand...
+          // deregister from that source
+          const count = source.deregister(port);
+            // Clean-up
+          if (count === 0) {
+            source.close();
+            sourcesByUrl[source.url] = null;
+          }
+        }
+        // Create a new Source
+        source = new Source(url);
+        source.register(port);
+        sourcesByUrl[url] = source;
+        sourcesByPort[port] = source;
+        return;
+      } else if (event.data.type === 'listen') {
+        const source = sourcesByPort[port];
+        source.listen(event.data.eventType);
+        return;
+      } else if (event.data.type === 'close') {
+        const source = sourcesByPort[port];
+
+        if (!source) return;
+
+        const count = source.deregister(port);
+        if (count === 0) {
+          source.close();
+          sourcesByUrl[source.url] = null;
+          sourcesByPort[port] = null;
+        }
+        return;
+      } else if (event.data.type === 'status') {
+        const source = sourcesByPort[port];
+        if (!source) {
+          port.postMessage({
+            type: 'status',
+            message: 'not connected',
+          });
+          return;
+        }
+        source.status(port);
+        return;
+      } else {
+        // just send it back
+        port.postMessage({
+          type: 'error',
+          message: `received but don't know how to handle: ${event.data}`,
+        });
+        return;
+      }
+    });
+    port.start();
+  }
+};
diff --git a/web_src/js/features/notification.js b/web_src/js/features/notification.js
index 0ea7f93c8d..2b7fc45237 100644
--- a/web_src/js/features/notification.js
+++ b/web_src/js/features/notification.js
@@ -18,7 +18,25 @@ export function initNotificationsTable() {
   });
 }
 
-export function initNotificationCount() {
+async function receiveUpdateCount(event) {
+  try {
+    const data = JSON.parse(event.data);
+
+    const notificationCount = document.querySelector('.notification_count');
+    if (data.Count > 0) {
+      notificationCount.classList.remove('hidden');
+    } else {
+      notificationCount.classList.add('hidden');
+    }
+
+    notificationCount.text(`${data.Count}`);
+    await updateNotificationTable();
+  } catch (error) {
+    console.error(error, event);
+  }
+}
+
+export async function initNotificationCount() {
   const notificationCount = $('.notification_count');
 
   if (!notificationCount.length) {
@@ -26,36 +44,57 @@ export function initNotificationCount() {
   }
 
   if (NotificationSettings.EventSourceUpdateTime > 0 && !!window.EventSource) {
-    // Try to connect to the event source first
-    const source = new EventSource(`${AppSubUrl}/user/events`);
-    source.addEventListener('notification-count', async (e) => {
-      try {
-        const data = JSON.parse(e.data);
-
-        const notificationCount = $('.notification_count');
-        if (data.Count === 0) {
-          notificationCount.addClass('hidden');
+    // Try to connect to the event source via the shared worker first
+    if (window.SharedWorker) {
+      const worker = new SharedWorker(`${__webpack_public_path__}js/eventsource.sharedworker.js`, 'notification-worker');
+      worker.addEventListener('error', (event) => {
+        console.error(event);
+      });
+      worker.port.onmessageerror = () => {
+        console.error('Unable to deserialize message');
+      };
+      worker.port.postMessage({
+        type: 'start',
+        url: `${window.location.origin}${AppSubUrl}/user/events`,
+      });
+      worker.port.addEventListener('message', (e) => {
+        if (!e.data || !e.data.type) {
+          console.error(e);
+          return;
+        }
+        if (event.data.type === 'notification-count') {
+          receiveUpdateCount(e.data);
+          return;
+        } else if (event.data.type === 'error') {
+          console.error(e.data);
+          return;
+        } else if (event.data.type === 'logout') {
+          if (e.data !== 'here') {
+            return;
+          }
+          worker.port.postMessage({
+            type: 'close',
+          });
+          worker.port.close();
+          window.location.href = AppSubUrl;
+          return;
         } else {
-          notificationCount.removeClass('hidden');
+          return;
         }
-
-        notificationCount.text(`${data.Count}`);
-        await updateNotificationTable();
-      } catch (error) {
-        console.error(error);
-      }
-    });
-    source.addEventListener('logout', async (e) => {
-      if (e.data !== 'here') {
-        return;
-      }
-      source.close();
-      window.location.href = AppSubUrl;
-    });
-    window.addEventListener('beforeunload', () => {
-      source.close();
-    });
-    return;
+      });
+      worker.port.addEventListener('error', (e) => {
+        console.error(e);
+      });
+      worker.port.start();
+      window.addEventListener('beforeunload', () => {
+        worker.port.postMessage({
+          type: 'close',
+        });
+        worker.port.close();
+      });
+
+      return;
+    }
   }
 
   if (NotificationSettings.MinTimeout <= 0) {
diff --git a/web_src/js/index.js b/web_src/js/index.js
index 0cfba4c66a..15ca32cfdc 100644
--- a/web_src/js/index.js
+++ b/web_src/js/index.js
@@ -2432,7 +2432,6 @@ $(document).ready(async () => {
   initContextPopups();
   initTableSort();
   initNotificationsTable();
-  initNotificationCount();
 
   // Repo clone url.
   if ($('#repo-clone-url').length > 0) {
@@ -2477,6 +2476,7 @@ $(document).ready(async () => {
     initClipboard(),
     initUserHeatmap(),
     initServiceWorker(),
+    initNotificationCount(),
   ]);
 });