RabbitMQ備用交換機和死信隊列設置出現type 'longstr' but current is none

 AlternateExchange是RabbitMQ中自定義的備用交換機的名稱

Channel shutdown: channel error; protocol method: #method<channel.close>(reply-code=406, reply-text=PRECONDITION_FAILED - inequivalent arg 'alternate-exchange' for exchange 'FruitDirectExchange' in vhost '/': received the value 'AlternateExchange' of type 'longstr' but current is none, class-id=40, method-id=10)

原因：queue已經存在，但是啓動時試圖設定一個 x-dead-letter-exchange 參數，這和服務器上的定義不一樣，server 不允許所以報錯。如果刪除 queue 重新 declare 則不會有問題。或者通過 policy 來設置這個參數也可以不用刪除隊列。