From 7fd98a5e8659f26f5015e4c3b46cf64fb8c3c9fd Mon Sep 17 00:00:00 2001
From: epriestley <git@epriestley.com>
Date: Mon, 17 Apr 2017 17:00:46 -0700
Subject: [PATCH] Every so often, ask the Aphict server how things are going

Summary: Ref T12573. This sends a "ping" to the server, and a "pong" back to the client, every 15 seconds. This tricks ELBs into thinking we're doing something useful and productive.

Test Plan: Ran `bin/aphlict debug`, loaded Phabricator, saw ping/pong in logs.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T12573

Differential Revision: https://secure.phabricator.com/D17717
---
 resources/celerity/map.php                    | 20 ++++++++--------
 .../aphlict/server/lib/AphlictClientServer.js | 12 ++++++++++
 .../rsrc/js/application/aphlict/Aphlict.js    | 23 +++++++++++++++++++
 3 files changed, 45 insertions(+), 10 deletions(-)

diff --git a/resources/celerity/map.php b/resources/celerity/map.php
index 43dade07f9..4bf38f9e57 100644
--- a/resources/celerity/map.php
+++ b/resources/celerity/map.php
@@ -10,7 +10,7 @@ return array(
     'conpherence.pkg.css' => 'a34d59bd',
     'conpherence.pkg.js' => '5f86c17d',
     'core.pkg.css' => '959330a2',
-    'core.pkg.js' => '349e50d5',
+    'core.pkg.js' => '4a83713e',
     'darkconsole.pkg.js' => '1f9a31bc',
     'differential.pkg.css' => '90b30783',
     'differential.pkg.js' => 'ddfeb49b',
@@ -361,7 +361,7 @@ return array(
     'rsrc/image/texture/table_header.png' => '5c433037',
     'rsrc/image/texture/table_header_hover.png' => '038ec3b9',
     'rsrc/image/texture/table_header_tall.png' => 'd56b434f',
-    'rsrc/js/application/aphlict/Aphlict.js' => '6304947a',
+    'rsrc/js/application/aphlict/Aphlict.js' => '674e335f',
     'rsrc/js/application/aphlict/behavior-aphlict-dropdown.js' => 'caade6f2',
     'rsrc/js/application/aphlict/behavior-aphlict-listen.js' => '06e7f30e',
     'rsrc/js/application/aphlict/behavior-aphlict-status.js' => '5e2634b9',
@@ -583,7 +583,7 @@ return array(
     'herald-rule-editor' => 'd6a7e717',
     'herald-test-css' => 'a52e323e',
     'inline-comment-summary-css' => '51efda3a',
-    'javelin-aphlict' => '6304947a',
+    'javelin-aphlict' => '674e335f',
     'javelin-behavior' => '61cbc29a',
     'javelin-behavior-aphlict-dropdown' => 'caade6f2',
     'javelin-behavior-aphlict-listen' => '06e7f30e',
@@ -1391,19 +1391,19 @@ return array(
       'javelin-install',
       'javelin-util',
     ),
-    '6304947a' => array(
-      'javelin-install',
-      'javelin-util',
-      'javelin-websocket',
-      'javelin-leader',
-      'javelin-json',
-    ),
     '635de1ec' => array(
       'javelin-behavior',
       'javelin-stratcom',
       'javelin-workflow',
       'javelin-dom',
     ),
+    '674e335f' => array(
+      'javelin-install',
+      'javelin-util',
+      'javelin-websocket',
+      'javelin-leader',
+      'javelin-json',
+    ),
     '680ea2c8' => array(
       'javelin-install',
       'javelin-dom',
diff --git a/support/aphlict/server/lib/AphlictClientServer.js b/support/aphlict/server/lib/AphlictClientServer.js
index b008d02bca..0d23d4f4f1 100644
--- a/support/aphlict/server/lib/AphlictClientServer.js
+++ b/support/aphlict/server/lib/AphlictClientServer.js
@@ -153,6 +153,18 @@ JX.install('AphlictClientServer', {
               }
               break;
 
+            case 'ping':
+              var pong = {
+                type: 'pong'
+              };
+
+              try {
+                listener.writeMessage(pong);
+              } catch (error) {
+                // Ignore any issues here, we'll clean up elsewhere.
+              }
+              break;
+
             default:
               log(
                 'Unrecognized command "%s".',
diff --git a/webroot/rsrc/js/application/aphlict/Aphlict.js b/webroot/rsrc/js/application/aphlict/Aphlict.js
index 529a974ab8..b2d7ec3215 100644
--- a/webroot/rsrc/js/application/aphlict/Aphlict.js
+++ b/webroot/rsrc/js/application/aphlict/Aphlict.js
@@ -41,6 +41,7 @@ JX.install('Aphlict', {
     _subscriptions: null,
     _status: null,
     _isReconnect: false,
+    _keepaliveInterval: false,
 
     start: function() {
       JX.Leader.listen('onBecomeLeader', JX.bind(this, this._lead));
@@ -104,6 +105,14 @@ JX.install('Aphlict', {
 
       this._broadcastStatus('open');
       JX.Leader.broadcast(null, {type: 'aphlict.getsubscribers'});
+
+      // By default, ELBs terminate connections after 60 seconds with no
+      // traffic. Other load balancers may have similar configuration. Send
+      // a keepalive message every 15 seconds to prevent load balancers from
+      // deciding they can reap this connection.
+
+      var keepalive = JX.bind(this, this._keepalive);
+      this._keepaliveInterval = setInterval(keepalive, 15000);
     },
 
     _didReconnect: function() {
@@ -124,6 +133,11 @@ JX.install('Aphlict', {
     },
 
     _close: function() {
+      if (this._keepaliveInterval) {
+        clearInterval(this._keepaliveInterval);
+        this._keepaliveInterval = null;
+      }
+
       this._broadcastStatus('closed');
     },
 
@@ -135,6 +149,11 @@ JX.install('Aphlict', {
       var message = JX.JSON.parse(raw);
       var id = message.uniqueID || null;
 
+      // If this is just a keepalive response, don't bother broadcasting it.
+      if (message.type == 'pong') {
+        return;
+      }
+
       JX.Leader.broadcast(id, {type: 'aphlict.server', data: message});
     },
 
@@ -198,6 +217,10 @@ JX.install('Aphlict', {
       };
 
       return this._write(frame);
+    },
+
+    _keepalive: function() {
+      this._writeCommand('ping', null);
     }
 
   },