MQTT Support, Messages Load Balancing and Delivery Guarantees

[WalManas]

Hello,

According to the documentation, ejabberd supports both MQTT 3.1.1 and 5 without providing a client library or any more details about what is exactly supported in MQTT. I have a couple of questions about the MQTT support.

1. Does ejabberd support MQTT shared subscriptions? If not, is there is any way in ejabberd to load balance messages over multiple clients such that a message is only consumed by one consumer among a group of consumers subscribing to the same node/topic?
2. Does ejabberd support MQTT durable subscriptions? If not, does ejabberd keeps messages around for a failed consumer so it can consume them upon recovery?
3. Does ejabberd support all of MQTT Quality of Services (QoS 0, QoS 1 and QoS 2)? If not, what are the delivery guarantees from a sender to ejabberd XMPP? I mean, if a sender sends a message, is there's away to get a delivery receipt from the server? What does the sender do in case such a receipt is not received? and if the server receives a message two times due to some failure, does it de-duplicate it?

Thanks in advance, and sorry for any inconvenience.

Wael.