Say you have a web page that is supposed to continuously update the
positions of ships in the ocean or something similar. I am wondering
what is a good approach for this ? The page updates automatically
without the user hitting any buttons or clicking on anything.
What occurs to me is a timer that goes off in JavaScript every couple
of seconds and sends a request to the Rails server. The Rails server
may send back a Javascript call or a series of calls with some data in
order to update the position of the ships. Basically the ships
positions are maintained on the server which gets live feeds of where
the ships are.
I have done similar types of things such as periodically_update() in
rails. Sometimes these polling type things get carried away and tons
of them get sent to the server. It could be that say there are 10
clients and each of them sends a request every couple of seconds so
now you have basically that many more requests and so on. Also if the
server gets behind on requests, the client keeps on sending them. For
whatever reason, it seems like a pain in the neck these types of
polling actions. They seem to clutter up the log file really bad and
possibly slow everything down in some situations. but I am not sure if
there is any other way to do this ?
If not is there a more optimal way to approach the polling I wonder ?
positions are maintained on the server which gets live feeds of where
possibly slow everything down in some situations. but I am not sure
if
there is any other way to do this ?
If not is there a more optimal way to approach the polling I wonder ?
I’ll add another railscast that appeared a few weeks later that might
make implementing a push server even
easier:#316 Private Pub - RailsCasts
What is the basic concept here ? Is this standard HTML/Javascript ?
Everything in HTTP seems counter to that I have seen, so I am missing
something ?
Web technology has advanced quite a bit over the years. One feature of
HTML5 is Websockets, which allow a persistent connection with the
server and thus allowing the server to push data to the client without
any client interaction or workarounds like polling with a certain
interval.
Frameworks like Faye use Websockets when available and fall back to
alternative methods for older browsers (a Flash-based socket or long
polling, which is not the same as interval polling).
Simply put (it’s actually a bit more complex) the following happens:
User loads the page
Javascript opens a persistent socket to the Faye server (using a
named channel if you want it to)
From your Rails app, you send messages to the Faye server, which
automatically distributes it to all client connections for that
particular channel.
The Railscasts explain the concept quite nicely IIRC.
