diff --git a/lib/connectionQueue.js b/lib/connectionQueue.js
new file mode 100644
index 00000000..f2bf9c8c
--- /dev/null
+++ b/lib/connectionQueue.js
@@ -0,0 +1,75 @@
+'use strict'
+
+const EventEmitter = require('events').EventEmitter
+
+/**
+ * Queuing Class for connection queuing
+ */
+
+const ConnectionQueueEvent = {
+  Tick: 'Tick'
+}
+
+class ConnectionQueue extends EventEmitter {
+  constructor (maximumLength, triggerTimeInterval = 10) {
+    super()
+    this.max = maximumLength
+    this.triggerTime = triggerTimeInterval
+    this.queue = []
+    this.lock = false
+
+    this.on(ConnectionQueueEvent.Tick, () => {
+      if (this.lock) return
+      setImmediate(() => {
+        this.process()
+      })
+    })
+  }
+
+  start () {
+    if (this.eventTrigger) return
+    this.eventTrigger = setInterval(() => {
+      this.emit(ConnectionQueueEvent.Tick)
+    }, this.triggerTime)
+  }
+
+  stop () {
+    if (this.eventTrigger) {
+      clearInterval(this.eventTrigger)
+      this.eventTrigger = null
+    }
+  }
+
+  /**
+   * push a promisify-task to queue
+   * @param task {Promise}
+   * @returns {boolean} if success return true, otherwise flase
+   */
+  push (task) {
+    if (this.queue.length >= this.max) return false
+    this.queue.push(task)
+    this.start()
+    return true
+  }
+
+  process () {
+    if (this.lock) return
+    this.lock = true
+    if (this.queue.length <= 0) {
+      this.stop()
+      this.lock = false
+      return
+    }
+    const task = this.queue.shift()
+
+    const finishTask = () => {
+      this.lock = false
+      setImmediate(() => {
+        this.process()
+      })
+    }
+    task().then(finishTask).catch(finishTask)
+  }
+}
+
+exports.ConnectionQueue = ConnectionQueue
diff --git a/test/connectionQueue.test.js b/test/connectionQueue.test.js
new file mode 100644
index 00000000..589d865b
--- /dev/null
+++ b/test/connectionQueue.test.js
@@ -0,0 +1,130 @@
+/* eslint-env node, mocha */
+'use strict'
+
+const assert = require('assert')
+const sinon = require('sinon')
+
+const ConnectionQueuing = require('../lib/connectionQueue').ConnectionQueue
+
+describe('ConnectionQueue', function () {
+  let clock
+
+  beforeEach(() => {
+    clock = sinon.useFakeTimers({
+      toFake: ['setInterval']
+    })
+  })
+
+  afterEach(() => {
+    clock.restore()
+    sinon.restore()
+  })
+
+  it('should not accept more than maximum task', () => {
+    const queue = new ConnectionQueuing(2)
+    const task = async () => {
+    }
+
+    queue.start()
+    assert(queue.push(task))
+    assert(queue.push(task))
+    assert(queue.push(task) === false)
+  })
+
+  it('should run task every interval', (done) => {
+    const runningClock = []
+    const queue = new ConnectionQueuing(2)
+    const task = async () => {
+      runningClock.push(clock.now)
+    }
+    queue.start()
+    assert(queue.push(task))
+    assert(queue.push(task))
+    clock.tick(5)
+    setTimeout(() => {
+      clock.tick(5)
+    }, 1)
+    setTimeout(() => {
+      clock.tick(5)
+    }, 2)
+    setTimeout(() => {
+      clock.tick(5)
+    }, 3)
+    queue.stop()
+
+    setTimeout(() => {
+      assert(runningClock.length === 2)
+      done()
+    }, 10)
+  })
+
+  it('should not crash when repeat stop queue', () => {
+    const queue = new ConnectionQueuing(2, 10)
+    try {
+      queue.stop()
+      queue.stop()
+      queue.stop()
+      assert.ok(true)
+    } catch (e) {
+      assert.fail(e)
+    }
+  })
+
+  it('should run process when queue is empty', (done) => {
+    const queue = new ConnectionQueuing(2, 100)
+    const processSpy = sinon.spy(queue, 'process')
+    queue.start()
+    clock.tick(100)
+    setTimeout(() => {
+      assert(processSpy.called)
+      done()
+    }, 1)
+  })
+
+  it('should run process although error occurred', (done) => {
+    const queue = new ConnectionQueuing(2, 100)
+    const failedTask = sinon.spy(async () => {
+      throw new Error('error')
+    })
+    const normalTask = sinon.spy(async () => {
+    })
+    queue.start()
+    assert(queue.push(failedTask))
+    assert(queue.push(normalTask))
+    clock.tick(100)
+    setTimeout(() => {
+      clock.tick(100)
+    }, 1)
+    setTimeout(() => {
+      // assert(queue.queue.length === 0)
+      assert(failedTask.called)
+      assert(normalTask.called)
+      done()
+    }, 5)
+  })
+
+  it('should ignore trigger when event not complete', (done) => {
+    const queue = new ConnectionQueuing(2, 10)
+    const processSpy = sinon.spy(queue, 'process')
+    const longTask = async () => {
+      return new Promise((resolve) => {
+        setInterval(() => {
+          resolve()
+        }, 50)
+      })
+    }
+    queue.start()
+    queue.push(longTask)
+    clock.tick(10)
+    setTimeout(() => {
+      clock.tick(10)
+    }, 0)
+    setTimeout(() => {
+      clock.tick(10)
+    }, 1)
+    setTimeout(() => {
+      assert(processSpy.calledOnce)
+      done()
+    }, 2)
+  })
+})
diff --git a/test/realtime.test.js b/test/realtime.test.js
index e3d00f5d..718b4a86 100644
--- a/test/realtime.test.js
+++ b/test/realtime.test.js
@@ -701,5 +701,9 @@ describe('realtime', function () {
       })
     })
 
+    describe('permission', function () {
+
+    })
+
   })
 })