Hold recent messages in Aphlict so they can be replayed after clients reconnect

Summary:
Ref T12563. Before broadcasting messages from the server, store them in a history buffer.

A future change will let clients retrieve them.

Test Plan:
  - Used the web frontend to look at the buffer, reloaded over time, sent messages. Saw buffer size go up as I sent messages and fall after 60 seconds.
  - Set size to 4 messages, sent a bunch of messages, saw the buffer size max out at 4 messages.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T12563

Differential Revision: https://secure.phabricator.com/D17707

src/applications/config/controller/PhabricatorConfigClusterNotificationsController.php

@@ -103,10 +103,20 @@ final class PhabricatorConfigClusterNotificationsController
           new PhutilNumber(idx($details, 'messages.in')),
           new PhutilNumber(idx($details, 'messages.out')));
 
+        if (idx($details, 'history.size')) {
+          $history = pht(
+            '%s Held / %sms',
+            new PhutilNumber(idx($details, 'history.size')),
+            new PhutilNumber(idx($details, 'history.age')));
+        } else {
+          $history = pht('No Messages');
+        }
+
       } else {
         $uptime = null;
         $clients = null;
         $stats = null;
+        $history = null;
       }
 
       $status_view = array(
@@ -126,6 +136,7 @@ final class PhabricatorConfigClusterNotificationsController
         $uptime,
         $clients,
         $stats,
+        $history,
         $messages,
       );
     }
@@ -143,6 +154,7 @@ final class PhabricatorConfigClusterNotificationsController
           pht('Uptime'),
           pht('Clients'),
           pht('Messages'),
+          pht('History'),
           null,
         ))
       ->setColumnClasses(
@@ -155,6 +167,7 @@ final class PhabricatorConfigClusterNotificationsController
           null,
           null,
           null,
+          null,
           'wide',
         ));
 

support/aphlict/server/lib/AphlictAdminServer.js

@@ -17,6 +17,7 @@ JX.install('AphlictAdminServer', {
     server.on('request', JX.bind(this, this._onrequest));
     this._server = server;
     this._clientServers = [];
+    this._messageHistory = [];
   },
 
   properties: {
@@ -30,6 +31,7 @@ JX.install('AphlictAdminServer', {
     _messagesOut: null,
     _server: null,
     _startTime: null,
+    _messageHistory: null,
 
     getListenerLists: function(instance) {
       var clients = this.getClientServers();
@@ -121,14 +123,24 @@ JX.install('AphlictAdminServer', {
         total_count += list.getTotalListenerCount();
       }
 
+      var now = new Date().getTime();
+
+      var history_size = this._messageHistory.length;
+      var history_age = null;
+      if (history_size) {
+        history_age = (now - this._messageHistory[0].timestamp);
+      }
+
       var server_status = {
         'instance': instance,
-        'uptime': (new Date().getTime() - this._startTime),
+        'uptime': (now - this._startTime),
         'clients.active': active_count,
         'clients.total': total_count,
         'messages.in': this._messagesIn,
         'messages.out': this._messagesOut,
-        'version': 7
+        'version': 7,
+        'history.size': history_size,
+        'history.age': history_age
       };
 
       response.writeHead(200, {'Content-Type': 'application/json'});
@@ -140,6 +152,16 @@ JX.install('AphlictAdminServer', {
      * Transmits a message to all subscribed listeners.
      */
     _transmit: function(instance, message, response) {
+      var now = new Date().getTime();
+
+      this._messageHistory.push(
+        {
+          timestamp: now,
+          message: message
+        });
+
+      this._purgeHistory();
+
       var peer_list = this.getPeerList();
 
       message = peer_list.addFingerprint(message);
@@ -191,7 +213,50 @@ JX.install('AphlictAdminServer', {
             error);
         }
       }
+    },
+
+    getHistory: function(min_age) {
+      var history = this._messageHistory;
+      var results = [];
+
+      for (var ii = 0; ii < history.length; ii++) {
+        if (history[ii].timestamp >= min_age) {
+          results.push(history[ii].message);
         }
       }
 
+      return results;
+    },
+
+    _purgeHistory: function() {
+      var messages = this._messageHistory;
+
+      // Maximum number of messages to retain.
+      var size_limit = 4096;
+
+      // Find the index of the first item we're going to keep. If we have too
+      // many items, this will be somewhere past the beginning of the list.
+      var keep = Math.max(0, messages.length - size_limit);
+
+      // Maximum number of milliseconds of history to retain.
+      var age_limit = 60000;
+
+      // Move the index forward until we find an item that is recent enough
+      // to retain.
+      var now = new Date().getTime();
+      var min_age = (now - age_limit);
+      for (keep; keep < messages.length; keep++) {
+        if (messages[keep].timestamp >= min_age) {
+          break;
+        }
+      }
+
+      // Throw away extra messages.
+      if (keep) {
+        this._messageHistory.splice(0, keep);
+      }
+    }
+
+  }
+
 });