FIX: display warning when user is tracking too many topics

FEATURE: allow admins to bump up number of tracked topics if needed
using max_tracked_new_unread

app/assets/javascripts/discourse/controllers/discovery/topics.js.es6

@@ -95,6 +95,10 @@ const controllerOpts = {
     return this.get('model.filter') === 'new' && this.get('model.topics.length') > 0;
   }.property('model.filter', 'model.topics.length'),
 
+  tooManyTracked: function(){
+      return Discourse.TopicTrackingState.current().tooManyTracked();
+  }.property(),
+
   showDismissAtTop: function() {
     return (this.isFilterPage(this.get('model.filter'), 'new') ||
            this.isFilterPage(this.get('model.filter'), 'unread')) &&

app/assets/javascripts/discourse/models/topic-tracking-state.js.es6

@@ -237,6 +237,10 @@ const TopicTrackingState = Discourse.Model.extend({
       .length;
   },
 
+  tooManyTracked() {
+    return this.initialStatesLength >= Discourse.SiteSettings.max_tracked_new_unread;
+  },
+
   resetNew() {
     const self = this;
     Object.keys(this.states).forEach(function (id) {
@@ -308,6 +312,7 @@ TopicTrackingState.reopenClass({
           instance = Discourse.TopicTrackingState.create({ messageBus, currentUser });
 
     instance.loadStates(data);
+    instance.initialStatesLength = data && data.length;
     instance.establishChannels();
     return instance;
   },

app/assets/javascripts/discourse/templates/discovery/topics.hbs

@@ -1,3 +1,7 @@
+{{#if tooManyTracked}}
+  <div class="alert alert-info">{{i18n 'topics.too_many_tracked'}}</div>
+{{/if}}
+
 {{#if redirectedReason}}
   <div class="alert alert-info">{{redirectedReason}}</div>
 {{/if}}

app/models/topic_tracking_state.rb

@@ -166,7 +166,7 @@ SQL
       sql << " AND topics.id = :topic_id"
     end
 
-    sql << " ORDER BY topics.bumped_at DESC ) SELECT * FROM x LIMIT 500"
+    sql << " ORDER BY topics.bumped_at DESC ) SELECT * FROM x LIMIT #{SiteSetting.max_tracked_new_unread.to_i}"
 
     SqlBuilder.new(sql)
       .map_exec(TopicTrackingState, user_id: user_id, topic_id: topic_id)

config/locales/client.en.yml

@@ -936,6 +936,7 @@ en:
     current_user: 'go to your user page'
 
     topics:
+      too_many_tracked: "Warning: you have too many tracked new and unread topics, clear some using \"Dismiss New\" or \"Dismiss Posts\""
       bulk:
         reset_read: "Reset Read"
         delete: "Delete Topics"

config/locales/server.en.yml

@@ -946,6 +946,7 @@ en:
 
     active_user_rate_limit_secs: "How frequently we update the 'last_seen_at' field, in seconds"
     verbose_localization: "Show extended localization tips in the UI"
+    max_tracked_new_unread: "Cap the total of new + unread topics per user, this protects database and client from very large payloads for some users tracking thousands of topics"
     previous_visit_timeout_hours: "How long a visit lasts before we consider it the 'previous' visit, in hours"
 
     rate_limit_create_topic: "After creating a topic, users must wait (n) seconds before creating another topic."

config/site_settings.yml

@@ -748,6 +748,9 @@ developer:
   migrate_to_new_scheme:
     hidden: true
     default: false
+  max_tracked_new_unread:
+    default: 1000
+    client: true
 
 embedding:
   feed_polling_enabled: