poll the backend for active users instead of keeping the connection open so it does not hang on a process w/ burnettk

spiffworkflow-backend/src/spiffworkflow_backend/routes/active_users_controller.py

@@ -1,11 +1,10 @@
 import json
 import time
-from typing import Generator
 
 import flask.wrappers
-from flask import current_app
 from flask import g
-from flask import stream_with_context
+from flask import jsonify
+from flask import make_response
 from flask.wrappers import Response
 
 from spiffworkflow_backend.models.active_user import ActiveUserModel
@@ -24,20 +23,11 @@ def active_user_updates(last_visited_identifier: str) -> Response:
         db.session.add(active_user)
         db.session.commit()
 
-    return Response(
-        stream_with_context(_active_user_updates(last_visited_identifier, active_user=active_user)),
-        mimetype="text/event-stream",
-        headers={"X-Accel-Buffering": "no"},
-    )
-
-
-def _active_user_updates(last_visited_identifier: str, active_user: ActiveUserModel) -> Generator[str, None, None]:
-    while True:
     active_user.last_seen_in_seconds = round(time.time())
     db.session.add(active_user)
     db.session.commit()
 
-        cutoff_time_in_seconds = time.time() - 15
+    cutoff_time_in_seconds = time.time() - 30
     active_users = (
         UserModel.query.join(ActiveUserModel)
         .filter(ActiveUserModel.last_visited_identifier == last_visited_identifier)
@@ -45,9 +35,7 @@ def _active_user_updates(last_visited_identifier: str, active_user: ActiveUserMo
         .filter(UserModel.id != g.user.id)
         .all()
     )
-        yield f"data: {current_app.json.dumps(active_users)} \n\n"
+    return make_response(jsonify(active_users), 200)
-
-        time.sleep(5)
 
 
 def active_user_unregister(last_visited_identifier: str) -> flask.wrappers.Response:

spiffworkflow-frontend/src/helpers.tsx

@@ -247,15 +247,21 @@ export const splitProcessModelId = (processModelId: string) => {
 export const refreshAtInterval = (
   interval: number,
   timeout: number,
-  func: Function
+  periodicFunction: Function,
+  cleanupFunction?: Function
 ) => {
-  const intervalRef = setInterval(() => func(), interval * 1000);
+  const intervalRef = setInterval(() => periodicFunction(), interval * 1000);
-  const timeoutRef = setTimeout(
+  const timeoutRef = setTimeout(() => {
-    () => clearInterval(intervalRef),
+    clearInterval(intervalRef);
-    timeout * 1000
+    if (cleanupFunction) {
-  );
+      cleanupFunction();
+    }
+  }, timeout * 1000);
   return () => {
     clearInterval(intervalRef);
+    if (cleanupFunction) {
+      cleanupFunction();
+    }
     clearTimeout(timeoutRef);
   };
 };

spiffworkflow-frontend/src/routes/ProcessModelEditDiagram.tsx

@@ -25,9 +25,7 @@ import Col from 'react-bootstrap/Col';
 import Editor, { DiffEditor } from '@monaco-editor/react';
 
 import MDEditor from '@uiw/react-md-editor';
-import { fetchEventSource } from '@microsoft/fetch-event-source';
+import HttpService from '../services/HttpService';
-import { BACKEND_BASE_URL } from '../config';
-import HttpService, { getBasicHeaders } from '../services/HttpService';
 import ReactDiagramEditor from '../components/ReactDiagramEditor';
 import ProcessBreadcrumb from '../components/ProcessBreadcrumb';
 import useAPIError from '../hooks/UseApiError';
@@ -35,6 +33,8 @@ import {
   makeid,
   modifyProcessIdentifierForPathParam,
   encodeBase64,
+  refreshAtInterval,
+  REFRESH_TIMEOUT_SECONDS,
 } from '../helpers';
 import {
   CarbonComboBoxProcessSelection,
@@ -134,6 +134,12 @@ export default function ProcessModelEditDiagram() {
 
   const lastVisitedIdentifier = encodeBase64(window.location.pathname);
   useEffect(() => {
+    const updateActiveUsers = () => {
+      HttpService.makeCallToBackend({
+        path: `/active-users/updates/${lastVisitedIdentifier}`,
+        successCallback: setActiveUsers,
+      });
+    };
     // Grab all available process models in case we need to search for them.
     // Taken from the Process Group List
     const processResults = (result: any) => {
@@ -155,30 +161,14 @@ export default function ProcessModelEditDiagram() {
         successCallback: setActiveUsers,
       });
     };
-    fetchEventSource(
+    updateActiveUsers();
-      `${BACKEND_BASE_URL}/active-users/updates/${lastVisitedIdentifier}`,
-      {
-        headers: getBasicHeaders(),
-        onmessage(ev) {
-          const retValue = JSON.parse(ev.data);
-          if ('error_code' in retValue) {
-            addError(retValue);
-          } else {
-            setActiveUsers(retValue);
-          }
-        },
-        onclose() {
-          unregisterUser();
-        },
-        onerror(err: any) {
-          throw err;
-        },
-      }
-    );
 
-    // FIXME: this is not getting called when navigating away from this page.
+    return refreshAtInterval(
-    // we do not know why yet.
+      15,
-    return unregisterUser;
+      REFRESH_TIMEOUT_SECONDS,
+      updateActiveUsers,
+      unregisterUser
+    );
     // eslint-disable-next-line react-hooks/exhaustive-deps
   }, []); // it is critical to only run this once.