nsqadmin: update in real-time

[pilwon]

It'd be great if we could see the numbers in nsqadmin (ex: Depth, Memory + Disk, Messages, Channels, etc.) updated in real-time via websocket.

[paddycarver]

Chiming in here quick: websockets are unnecessary for this, as you don't need two way communication. Just use Server Sent Events. They're trivial to implement in Go.

[mreiferson]

updated title :)

[paddycarver]

They also are easier to operate. No worrying about reconnect logic, they mostly "just work" for streaming updates.

[jamesfzhang]

👍

[zygis]

+1

[stephens2424]

Websockets have marginally more support across browsers (latest IE versions being the notable one missing from Server Sent Events).

http://caniuse.com/#search=server vs http://caniuse.com/#search=websocket

Does anybody have any significant opinion on which to use, with that in mind?

[mreiferson]

I would say whichever is simpler to implement - I'm not terribly concerned about IE compatibility, for example.

[paddycarver]

I'd say SSE--implementing it in Go is trivial, the client-side code is simpler (no need to manage connection state, etc.) and the main advantage of WS (the client can talk to the server) isn't something nsqadmin actually needs.

[allgeek]

It's less elegant than a full SSE implementation, but as part of #323 it should be trivial to implement an automatic refresh on a configurable timer, with the client re-polling for new data over the nsqadmind REST endpoints. I think SSE should be tackled in a separate commit for this issue after that initial refactoring, but welcome input in #323 if there are any suggestions/concerns with that sort of interim solution.