Multi-node MQTT server

[raj-cg]

We are trying to implement a high-availability MQTT service using mochi, If a persistence layer of Redis is added then multiple nodes of mochi should be able to connect to the same Redis backend and retain session data in Redis,

Also is there a need for sticky sessions when working with load balancers?

Is there any additional work required to create a HA setup?
Please let me know if I missed anything here.

[dhruvjain99]

How do you plan to pass messages around for scenarios in which clients are on different nodes for which the message needs to be routed?

[RohanDoshi21]

What could the different approaches be?

I was thinking of

1. Broadcasting all publish messages to each node. ( filter out based upon if client is connected to me, avoid loops but not further broadcasting if processing a broadcasted message )

2. Using Redis Pub-Sub. ( Each node will be a redis client subscriber ), but this doesn't guarantee message delivery.

3. Using Redis streams, and clearing out old messages periodically / clearing out messages after grp ack is received.

Stuck at making a design decision, trying to create a clustered setup, for a college project!
Any thoughts upon this @dhruvjain99 @raj-cg @wind-c

[wind-c]

Comqtt's cluster capability was developed based on mochi-co/mqtt v2.0.
It uses gossip for node discovery and raft for data(subscribe/unsubscribe) consistency synchronization. It uses redis to store inflight, retain messages and subscriptions across nodes.Publish messages are routed to the corresponding node according to the subscription table. For reference.

[torntrousers]

Comqtt's cluster capability was developed based on mochi-co/mqtt v2.0. It uses gossip for node discovery and raft for data(subscribe/unsubscribe) consistency synchronization. It uses redis to store inflight, retain messages and subscriptions across nodes.Publish messages are routed to the corresponding node according to the subscription table. For reference.

@wind-c - sounds really interesting - why not come up with some PR proposals to get that merged in here?