Redis pubsub with node js and web socket for Notification / Feed like system

[saurabh joshi]

Hi,

I am trying looking at various ways to develop Notification / Feed like system. Following approach is the one I am trying to implement.

Nodejs + websockets(socket.io) -> 

To maintain/ have persistent connection between client/user/receiver and server. This will allow for real time notification.

Redis pubsub -> As a key value store + mechanism(i.e. pubsub) through which node server can receiver latest message for given channels and depending on user subscriptions can forward to user using web socket connection.

Some articles I am following ->

how-disqus-went-realtime-with-165k-messages-per-second

bluemix-node-redis-app

highly-available-real-time-notifications - flicker.net

nodejs-three-ways -

Problem ->

After reading through these articles I am trying to use redis pubsub + node + socket.io. On reading posts in this group now I am somewhat doubtful about my understanding of redis pubsub and possibly the above mentioned articles.

1. Is my requirement a valid use case of redis pubsub.
2. Notifications delivered to user need to be persisted as after system has recorved from shutdown/ failure , user should get all pending notifications.
3. Actions/code that generates the notifications for example say a comment is added to some entity, is written in java and that action is stored in relational database like MySql/Oracle.Also these notifications need to be generated based on number of rules. So how do I publish / write notification data to 'pub' part of redis pubsub mechanism. 
4. The subscribers of channels/topics are called client. what is mean by client ? Some process/thread running on node or any server or it is the actual entity which will finally receive the notification like web app / APNS.
5. If not this then what is the better approach for this kind of project.

Need help. Please comment if also need any more clarification.

Thanks  

Saurabh.