shard the pending-updates-list queue

services/document-updater/app.js

@@ -34,7 +34,7 @@ app.use(Metrics.http.monitor(logger))
 app.use(bodyParser.json({ limit: Settings.maxJsonRequestSize }))
 Metrics.injectMetricsRoute(app)
 
-DispatchManager.createAndStartDispatchers(Settings.dispatcherCount || 10)
+DispatchManager.createAndStartDispatchers(Settings.dispatcherCount)
 
 app.param('project_id', (req, res, next, projectId) => {
   if (projectId != null && projectId.match(/^[0-9a-f]{24}$/)) {

services/document-updater/app/js/DispatchManager.js

@@ -20,13 +20,21 @@ const logger = require('logger-sharelatex')
 const Keys = require('./UpdateKeys')
 const redis = require('@overleaf/redis-wrapper')
 const Errors = require('./Errors')
+const _ = require('lodash')
 
 const UpdateManager = require('./UpdateManager')
 const Metrics = require('./Metrics')
 const RateLimitManager = require('./RateLimitManager')
 
 module.exports = DispatchManager = {
-  createDispatcher(RateLimiter) {
+  createDispatcher(RateLimiter, queueShardNumber) {
+    let pendingListKey
+    if (queueShardNumber === 0) {
+      pendingListKey = 'pending-updates-list'
+    } else {
+      pendingListKey = `pending-updates-list-${queueShardNumber}`
+    }
+
     const client = redis.createClient(Settings.redis.documentupdater)
     var worker = {
       client,
@@ -35,11 +43,8 @@ module.exports = DispatchManager = {
           callback = function (error) {}
         }
         const timer = new Metrics.Timer('worker.waiting')
-        return worker.client.blpop('pending-updates-list', 0, function (
-          error,
-          result
-        ) {
-          logger.log('getting pending-updates-list', error, result)
+        return worker.client.blpop(pendingListKey, 0, function (error, result) {
+          logger.log(`getting ${queueShardNumber}`, error, result)
           timer.done()
           if (error != null) {
             return callback(error)
@@ -103,15 +108,9 @@ module.exports = DispatchManager = {
   createAndStartDispatchers(number) {
     const RateLimiter = new RateLimitManager(number)
     return (() => {
-      const result = []
-      for (
-        let i = 1, end = number, asc = end >= 1;
-        asc ? i <= end : i >= end;
-        asc ? i++ : i--
-      ) {
-        const worker = DispatchManager.createDispatcher(RateLimiter)
-        result.push(worker.run())
-      }
+      const result = _.times(number, function (shardNumber) {
+        return DispatchManager.createDispatcher(RateLimiter, shardNumber).run()
+      })
       return result
     })()
   }

services/document-updater/config/settings.defaults.js

@@ -171,7 +171,7 @@ module.exports = {
   maxJsonRequestSize:
     parseInt(process.env.MAX_JSON_REQUEST_SIZE, 10) || 8 * 1024 * 1024,
 
-  dispatcherCount: process.env.DISPATCHER_COUNT,
+  dispatcherCount: process.env.DISPATCHER_COUNT || 10,
 
   mongo: {
     options: {

services/document-updater/test/acceptance/js/helpers/DocUpdaterClient.js

@@ -1,5 +1,6 @@
 let DocUpdaterClient
 const Settings = require('settings-sharelatex')
+const _ = require('lodash')
 const rclient = require('@overleaf/redis-wrapper').createClient(
   Settings.redis.documentupdater
 )
@@ -26,6 +27,15 @@ module.exports = DocUpdaterClient = {
     rclientSub.on('message', callback)
   },
 
+  _getPendingUpdateListKey() {
+    const shard = _.random(0, Settings.dispatcherCount)
+    if (shard === 0) {
+      return 'pending-updates-list'
+    } else {
+      return `pending-updates-list-${shard}`
+    }
+  },
+
   sendUpdate(projectId, docId, update, callback) {
     rclient.rpush(
       keys.pendingUpdates({ doc_id: docId }),
@@ -39,7 +49,12 @@ module.exports = DocUpdaterClient = {
           if (error) {
             return callback(error)
           }
-          rclient.rpush('pending-updates-list', docKey, callback)
+
+          rclient.rpush(
+            DocUpdaterClient._getPendingUpdateListKey(),
+            docKey,
+            callback
+          )
         })
       }
     )

services/document-updater/test/unit/js/DispatchManager/DispatchManagerTests.js

@@ -64,7 +64,8 @@ describe('DispatchManager', function () {
       this.client = { auth: sinon.stub() }
       this.redis.createClient = sinon.stub().returns(this.client)
       return (this.worker = this.DispatchManager.createDispatcher(
-        this.RateLimiter
+        this.RateLimiter,
+        0
       ))
     })
 
@@ -129,7 +130,7 @@ describe('DispatchManager', function () {
         })
       })
 
-      return describe("with a 'Delete component' error", function () {
+      describe("with a 'Delete component' error", function () {
         beforeEach(function () {
           this.UpdateManager.processOutstandingUpdatesWithLock = sinon
             .stub()
@@ -145,6 +146,28 @@ describe('DispatchManager', function () {
           return this.callback.called.should.equal(true)
         })
       })
+
+      describe('pending updates list with shard key', function () {
+        beforeEach(function (done) {
+          this.client = {
+            auth: sinon.stub(),
+            blpop: sinon.stub().callsArgWith(2)
+          }
+          this.redis.createClient = sinon.stub().returns(this.client)
+          this.queueShardNumber = 7
+          this.worker = this.DispatchManager.createDispatcher(
+            this.RateLimiter,
+            this.queueShardNumber
+          )
+          this.worker._waitForUpdateThenDispatchWorker(done)
+        })
+
+        it('should call redis with BLPOP with the correct key', function () {
+          this.client.blpop
+            .calledWith(`pending-updates-list-${this.queueShardNumber}`, 0)
+            .should.equal(true)
+        })
+      })
     })
 
     return describe('run', function () {