fix: prevent packets leaks in cluster env

aedes.js

@@ -79,10 +79,19 @@ function Aedes (opts) {
   this.brokers = {}
 
   const heartbeatTopic = $SYS_PREFIX + that.id + '/heartbeat'
+  const birthTopic = $SYS_PREFIX + that.id + '/birth'
+
   this._heartbeatInterval = setInterval(heartbeat, opts.heartbeatInterval)
 
   const bufId = Buffer.from(that.id, 'utf8')
 
+  // in a cluster env this is used to warn other broker instances
+  // that this broker is alive
+  that.publish({
+    topic: birthTopic,
+    payload: bufId
+  }, noop)
+
   function heartbeat () {
     that.publish({
       topic: heartbeatTopic,
@@ -141,6 +150,19 @@ function Aedes (opts) {
     done()
   })
 
+  this.mq.on($SYS_PREFIX + '+/birth', function brokerBorn (packet, done) {
+    const brokerId = packet.payload.toString()
+
+    // reset duplicates counter
+    if (brokerId !== that.id) {
+      for (const clientId in that.clients) {
+        delete that.clients[clientId].duplicates[brokerId]
+      }
+    }
+
+    done()
+  })
+
   this.mq.on($SYS_PREFIX + '+/new/clients', function closeSameClients (packet, done) {
     const serverId = packet.topic.split('/')[1]
     const clientId = packet.payload.toString()

test/events.js

@@ -1,6 +1,7 @@
 'use strict'
 
 const { test } = require('tap')
+const mqemitter = require('mqemitter')
 const { setup, connect, subscribe } = require('./helper')
 const aedes = require('../')
 
@@ -16,9 +17,49 @@ test('publishes an hearbeat', function (t) {
     const id = message.topic.match(/\$SYS\/([^/]+)\/heartbeat/)[1]
     t.equal(id, broker.id, 'broker id matches')
     t.same(message.payload.toString(), id, 'message has id as the payload')
+    cb()
   })
 })
 
+test('publishes birth', function (t) {
+  t.plan(4)
+
+  const mq = mqemitter()
+  const brokerId = 'test-broker'
+  const fakeBroker = 'fake-broker'
+  const clientId = 'test-client'
+
+  mq.on(`$SYS/${brokerId}/birth`, (message, cb) => {
+    t.pass('broker birth received')
+    t.same(message.payload.toString(), brokerId, 'message has id as the payload')
+    cb()
+  })
+
+  const broker = aedes({
+    id: brokerId,
+    mq
+  })
+
+  broker.on('client', (client) => {
+    t.equal(client.id, clientId, 'client connected')
+    // set a fake counter on a fake broker
+    process.nextTick(() => {
+      broker.clients[clientId].duplicates[fakeBroker] = 42
+      mq.emit({ topic: `$SYS/${fakeBroker}/birth`, payload: Buffer.from(fakeBroker) })
+    })
+  })
+
+  mq.on(`$SYS/${fakeBroker}/birth`, (message, cb) => {
+    process.nextTick(() => {
+      t.equal(!!broker.clients[clientId].duplicates[fakeBroker], false, 'client duplicates has been resetted')
+      cb()
+    })
+  })
+
+  const s = connect(setup(broker), { clientId })
+  t.teardown(s.broker.close.bind(s.broker))
+})
+
 ;['$mcollina', '$SYS'].forEach(function (topic) {
   test('does not forward $ prefixed topics to # subscription - ' + topic, function (t) {
     t.plan(4)

test/retain.js

@@ -275,7 +275,7 @@ test('new QoS 0 subscribers receive QoS 0 retained messages when clean', functio
   })
 
   clock.setTimeout(() => {
-    t.equal(broker.counter, 8)
+    t.equal(broker.counter, 9)
   }, 200)
 })
 
@@ -315,7 +315,7 @@ test('new QoS 0 subscribers receive downgraded QoS 1 retained messages when clea
     })
   })
   broker.on('closed', function () {
-    t.equal(broker.counter, 7)
+    t.equal(broker.counter, 8)
   })
 })