[Hawkular-dev] cmdgw forwarding messages from bus to UI

[Jiri Kremser]

Hello,
  when creating the topology graph, the nice feature would be to see the newly added resources in inventory in a real-time. Currently, the approach on many places in UI is polling with long intervals. Each 20 seconds the url list, app server list or topology is updated with the fresh data. 

We have the server-side bus in place into which inventory events when anyone is 'CRUDing' the entities, I believe alerts are being sent there, etc. Also we have the cmdgw module for dealing with the bus-agent-ui communication, it uses the WebSockets for full-duplex comm. From what I've seen it works like this:

1) ui initializes the WS connection
2) server stores the session, correlation id is the session id
3) later on ui invokes a command with some id
4) once the command is done the ui is notified by the server side (no polling, real server push)
+ some magic with bus (bus works here as a glue with the other components)

What would be imho really useful would be not only using the web socket layer for sending the responses on previously requested operations but also having the ability to send the notification to whoever cares on the ui (without any former explicit action in the ui). I mean events like "something bad happened". After talking with Peter, the better correlation id here is the tenant id, because we don't want to leak the information among the tenants. So if the server keeps the info which session id was created for which tenant we are almost there.

pros:
* alerts can be displayed immediately (no need to wait 20 seconds for the refresh)
* no polling = no wasting with resources
* cool demos

cons:
* switching the persona needs to be handled, but it's doable

What do you think?

jk