Fix #104: Manage, throttle comments with Redis

.travis.yml

@@ -2,3 +2,6 @@ language: node_js
 
 node_js:
   - "0.12"
+
+services:
+  - redis-server

CONTRIBUTING.md

@@ -11,7 +11,10 @@ the contribution workflow at this point.
    create a token
 4. From the terminal, add your newly created GitHub personal access token to the
    Heroku config:  heroku config:set OAUTH_TOKEN=#######
-5. Create a test repository which you'll send invalid CSS or Stylus files to,
+5. Enable the Heroku Redis add-on (you may need to enter a credit card for
+   verification): `heroku addons:create heroku-redis:hobby-dev`
+6. Start a worker: `heroku ps:scale worker=1`
+7. Create a test repository which you'll send invalid CSS or Stylus files to,
    which your Discord instance will evaluate. Within that repository:
     1. Navigate to *Settings* > *Webhooks and Services*
     2. Add a webhook
@@ -27,9 +30,24 @@ GitHub.
 
 # Submitting a pull request
 
-Before submitting a pull request, run the following commands to test your
-changes and spruce things up.
+Before submitting a pull request, follow these steps to spruce things up and
+test your changes.
 
-1. `npm install`
-2. `./gulp test`
-3. `./gulp beautify`
+## Setup
+
+To get started, install all dependencies and set up Redis:
+
+1. Run `npm install`
+2. Follow [these steps](http://redis.io/topics/quickstart#installing-redis)
+   to install a local Redis server
+
+## Beautify your code
+
+Run this command to format your code according to our conventions:
+
+`./gulp beautify`
+
+## Run tests
+
+1. Start the local Redis server
+2. Run `./gulp test`

Procfile

@@ -0,0 +1,2 @@
+web: node bin/www.js
+worker: node worker.js

commenter.js

@@ -8,15 +8,13 @@
 var sendRequest = require('request');
 
 var config = require('./config');
-var logger = require('./logger');
 
 /**
  * Post a line comment on a particular pull request. commentURL should be an
  * instance of review_comments_url.
  * https://developer.github.com/v3/activity/events/types/#pullrequestevent
  */
-function postPullRequestComment(commentURL, comment, filename, commitSHA, line) {
-
+function postPullRequestComment(commentURL, comment, filename, commitSHA, line, done) {
     sendRequest({
         url: commentURL,
         method: 'POST',
@@ -30,8 +28,14 @@ function postPullRequestComment(commentURL, comment, filename, commitSHA, line)
             commit_id: commitSHA,
             position: line
         })
-    }, function(error) {
-        if (error) return logger.error('Error posting pull request comment to ' + commentURL + ' regarding commit ' + commitSHA + ':', error);
+    }, function(error, response) {
+        // If the comment could not be submitted, notify Redis so that the job
+        // can be re-attempted later. Otherwise, mark the job as done.
+        if(error || response.statusCode === 403) {
+            return done(new Error('Comment could not be submitted'));
+        } else {
+            done();
+        }
     });
 }
 

config.js

@@ -2,6 +2,8 @@ var config = {
     brand: 'Discord',
     token: process.env.OAUTH_TOKEN,
     trackingID: process.env.TRACKING_ID,
+    commentWait: process.env.COMMENT_WAIT || 250,
+    commentAttempts: process.env.COMMENT_ATTEMPTS || 10,
 
     // Used when no environment variable (process.env.PORT) is set
     port: 3000,

hook.js

@@ -3,12 +3,12 @@
 var github = require('octonode');
 var Q = require('q');
 
-var commenter = require('./commenter');
 var diff = require('./diffParse');
 var logger = require('./logger');
 var processor = require('./processor');
 var utils = require('./utils');
 var config = require('./config');
+var redisQueue = require('./redisQueue');
 
 var configFilename = '.doiuse';
 var githubClient = github.client(config.token);
@@ -61,7 +61,32 @@ function processPullRequest(destinationRepo, originRepo, originBranch, prNumber,
                     // Callback for handling an incompatible line of code
                     var line = diff.lineToIndex(file.patch, incompatibility.usage.source.start.line);
                     var comment = incompatibility.featureData.title + ' not supported by: ' + incompatibility.featureData.missing;
-                    commenter.postPullRequestComment(commentURL, comment, file.filename, currentCommit.sha, line);
+
+                    // Create a Redis job that will submit the comment
+                    var commentJob = redisQueue.create('comment', {
+                        commentURL: commentURL,
+                        sha: currentCommit.sha,
+                        filename: file.filename,
+                        line: line,
+                        comment: comment
+                    });
+
+                    // If the comment is rejected, re-attempt several times with
+                    // exponentially longer waits between each attempt.
+                    commentJob.attempts(config.commentAttempts);
+                    commentJob.backoff({
+                        type: 'exponential'
+                    });
+
+                    // If the comment is rejected after several attempts, log an
+                    // error.
+                    commentJob.on('failed', function() {
+                        logger.error('Error posting comment to line ' + line + ' of ' + file.filename + ' in ' + originRepo + ' pull request #' + prNumber);
+                    });
+
+                    commentJob.save(function(error) {
+                        if (error) return logger.error(error);
+                    });
                 });
 
             });

package.json

@@ -3,7 +3,6 @@
     "main": "app.js",
     "private": true,
     "scripts": {
-        "start": "node ./bin/www",
         "postinstall": "./gulp --gulpfile gulpfile-prod.js build",
         "test": "./gulp test"
     },
@@ -34,6 +33,7 @@
         "express": "^4.8.6",
         "gulp": "^3.8.11",
         "gulp-marked": "^1.0.0",
+        "kue": "^0.9.4",
         "newrelic": "^1.21.1",
         "nunjucks": "^1.3.4",
         "octonode": "^0.7.1",

redisQueue.js

@@ -0,0 +1,32 @@
+/**
+ * Return an instance of the Kue queue singleton.
+ *
+ * This file is only needed to work around bug #681 of Kue:
+ * https://github.com/Automattic/kue/issues/681
+ *
+ * Once the bugfix is shipped, we'll be able to get the queue with much less
+ * code, making this file unnecessary:
+ *
+ *     var kue = require('kue');
+ *     var redisQueue = kue.createQueue({
+ *         redis: process.env.REDIS_URL
+ *     });
+ */
+
+var kue = require('kue');
+var url = require('url');
+
+var parsedRedisURL = url.parse(process.env.REDIS_URL);
+
+var config = {
+    redis: {
+        port: parseInt(parsedRedisURL.port),
+        host: parsedRedisURL.hostname
+    }
+};
+
+if (parsedRedisURL.auth) {
+    config.redis.auth = parsedRedisURL.auth.replace(/.*?:/, '');
+}
+
+module.exports = kue.createQueue(config);

tests/tests.js

@@ -1,15 +1,20 @@
 'use strict';
 
-// Set environment variables that will be read during testing. These values will
-// be read in config.js, so they need to be set before the file is loaded.
+// Set environment variables that will be needed during testing. These values
+// will be read in config.js, so they need to be set before the file is loaded.
 var testedTrackingID = '654321';
 process.env.TRACKING_ID = testedTrackingID;
+process.env.REDIS_URL = 'redis://localhost';
+process.env.COMMENT_WAIT = 0; // The comment wait is only needed in production to avoid tripping a GitHub spam protection system
 
 // Pretend that we're running in production mode so that we can test
 // production-only features like Google Analytics tracking. This value is read
 // in app.js, so it needs to be set before the file is loaded.
 process.env.NODE_ENV = 'production';
 
+// Process Redis tasks
+require('../worker');
+
 var fs = require('fs');
 var path = require('path');
 

worker.js

@@ -0,0 +1,25 @@
+'use strict';
+
+var commenter = require('./commenter');
+var config = require('./config');
+var redisQueue = require('./redisQueue');
+
+var lastCommentTimestamp = 0;
+
+// Process comment jobs
+// Pause for commentWait milleseconds between comment submissions
+redisQueue.process('comment', function(job, done) {
+    var now = Date.now();
+    var waitRemaining = 0;
+
+    var nextCommentTimestamp = lastCommentTimestamp + parseInt(config.commentWait);
+
+    if (nextCommentTimestamp > now) {
+        waitRemaining = nextCommentTimestamp - now;
+    }
+
+    setTimeout(function() {
+        commenter.postPullRequestComment(job.data.commentURL, job.data.comment, job.data.filename, job.data.sha, job.data.line, done);
+        lastCommentTimestamp = Date.now(); // Use a new, fresh timestamp
+    }, waitRemaining);
+});