I found two links on these exchanges. https://www.rabbitmq.com/federated-exchanges.html and https://www.rabbitmq.com/ae.html but could not get it what Author was trying to say. Has anyone idea related to these two Exchange and one more question.
Is there any exchange in Which if client with routing key is not found then message is not discarded instead stored in a queue and when related routing key is found then it is ready to fetch?
Federated exchanges are used for replicating messages from one RabbitMQ server to another, in possibly remote machine.
The alternate exchange is there in order to route messages to that exchange in case the message couldn't be routed, because there are no bindings matching the message routing key. Of course you have to create said exchange, and then add it as alternate of the exchange where you publish your messages.
Using the alternate exchange and binding a queue to it, then you can get those messages that can't be routed into a queue and consume them, but there's no functionality to later re-route them once you have added the missing routing key. What you can do is just consume those messages and republish them.
