Rabbit MQ amqplib error “No channels left to allocate”

今天在查看node.js服務日誌的時候發現amqplib模塊報錯No channels left to allocate。是服務沒有複用通道，創建了太多的channel導致該問題，通過調試找到報錯的位置，在amqplib/lib/connection.js中freshChannel函數中報錯。
具體代碼如下：

// I use an array to keep track of the channels, rather than an
// object. The channel identifiers are numbers, and allocated by the
// connection. If I try to allocate low numbers when they are
// available (which I do, by looking from the start of the bitset),
// this ought to keep the array small, and out of 'sparse array
// storage'. I also set entries to null, rather than deleting them, in
// the expectation that the next channel allocation will fill the slot
// again rather than growing the array. See
// http://www.html5rocks.com/en/tutorials/speed/v8/
C.freshChannel = function(channel, options) {
  var next = this.freeChannels.nextClearBit(1);
  if (next < 0 || next > this.channelMax)
    throw new Error("No channels left to allocate");
  this.freeChannels.set(next);
  //
  此處省略多行代碼
  //
};

可以看出當創建的通道大於channelMax就會拋出該異常。而該channelMax的值是跟rabbitmq server協商來的。
調試在amqplib/lib/connection.js中afterStartOk函數，該函數用於根據服務器端傳入的數據來設置channelMax,heartbeat等通訊參數，函數代碼如下：

  function afterStartOk(reply) {
    switch (reply.id) {
    case defs.ConnectionSecure:
      bail(new Error(
        "Wasn't expecting to have to go through secure"));
      break;
    case defs.ConnectionClose:
      bail(new Error(fmt("Handshake terminated by server: %s",
                         closeMsg(reply))));
      break;
    case defs.ConnectionTune:
      var fields = reply.fields;//服務器段返回的通訊參數
      tunedOptions.frameMax =
        negotiate(fields.frameMax, allFields.frameMax);
      tunedOptions.channelMax =
        negotiate(fields.channelMax, allFields.channelMax);   //在這裏設置最大通道數
      tunedOptions.heartbeat =
        negotiate(fields.heartbeat, allFields.heartbeat);
      send(defs.ConnectionTuneOk);
      send(defs.ConnectionOpen);
      expect(defs.ConnectionOpenOk, onOpenOk);
      break;
    default:
      bail(new Error(
        fmt("Expected connection.secure, connection.close, " +
            "or connection.tune during handshake; got %s",
            inspect(reply, false))));
      break;
    }
  }

在我這個環境下服務器返回的最大通道數爲2047，由此最多可以創建2047個通道。