Re: [Rails] Forcing browser redirects on a Ruby on Rails application

[Colin Law]

On 19 April 2013 07:00, karan verma <karan....@gmail.com> wrote:
> Hi
>
> I am building a Rails application which aims at facilitating two users to
> collaborate on a web page based on their user id. The user matching process
> is a controlled one since the app is for research purposes. To support the
> same I am also building an admin interface which will allow the admin to
> match two users so that both of them are redirected to a certain webpage.
>
> How can I force the user browsers to redirect to a common page, that I
> selected?

You could save the redirect requirement in a table in the database,
with an appropriate relationship with the user, then use a before
filter in the controller to check whether a redirect is required and
do it.

Colin

[karan verma]

Thanks for the reply Colin. 

We do not know the user ids before hand. They will sign up for the research study, and the admin will decide which users to pair among the ones online. One user may be paired with three to four other users one after another. I want to have the admin control over the process so that we could pair a user with a third online user if one from the original pair got offline and did not return. So the decision about which url to redirect to must be made dynamically. 

Do you think the Table approach would still work in the above scenario? 

I was thinking of building some sort of a polling mechanism (i'm not super clear on how to do that as I am relatively new) where the browsers contact the server to confirm their online status. However I was confused as to how I could redirect two browsers to a common url.

I found this on stack-overflow: http://stackoverflow.com/questions/199099/how-to-manage-a-redirect-request-after-a-jquery-ajax-call/1534662#1534662 

Which seems to be a promising solution. What do you think? 

[Colin Law]

On 19 April 2013 09:43, karan verma <karan....@gmail.com> wrote:

Please don't top post it makes it difficult to follow the thread.
Insert your reply at appropriate points in the previous message.
Thanks

> Thanks for the reply Colin.
>
> We do not know the user ids before hand. They will sign up for the research
> study, and the admin will decide which users to pair among the ones online.
> One user may be paired with three to four other users one after another. I
> want to have the admin control over the process so that we could pair a user
> with a third online user if one from the original pair got offline and did
> not return. So the decision about which url to redirect to must be made
> dynamically.
>
> Do you think the Table approach would still work in the above scenario?
>
> I was thinking of building some sort of a polling mechanism (i'm not super
> clear on how to do that as I am relatively new) where the browsers contact
> the server to confirm their online status. However I was confused as to how
> I could redirect two browsers to a common url.
>
> I found this on stack-overflow:
> http://stackoverflow.com/questions/199099/how-to-manage-a-redirect-request-after-a-jquery-ajax-call/1534662#1534662
> Which seems to be a promising solution. What do you think?

Do you need the redirect to happen immediately the admin decides that
it should happen? My solution (with a before_filter) will only
redirect the next time the user requests a page. If you want it to
happen immediately then yes, you will need to poll the server from the
current page in the browser, using javascript.

Colin

[karan verma]

On 19 April 2013 09:43, karan verma <karan....@gmail.com> wrote:

Please don't top post it makes it difficult to follow the thread.
Insert your reply at appropriate points in the previous message.
Thanks

 

 Sure will keep that in mind. 

 

Do you need the redirect to happen immediately the admin decides that
it should happen?  My solution (with a before_filter) will only
redirect the next time the user requests a page.  If you want it to
happen immediately then yes, you will need to poll the server from the
current page in the browser, using javascript.

  Yes I need it to happen immediately the admin decides that it should happen. To implement the polling mechanism how can I enable the javascript to talk to the rails server? 

[Colin Law]

On 19 April 2013 20:28, karan verma <karan....@gmail.com> wrote:
> ..

> Yes I need it to happen immediately the admin decides that it should
> happen. To implement the polling mechanism how can I enable the javascript
> to talk to the rails server?

That is a javascript issue rather than a rails one. Have a look at
the javascript setTimeout function. However if you want to write
sophisticated web apps you really need a good knowledge of javascript.
I suggest working through some tutorials. Probably jQuery.

Colin

[Martin Gogov]

The table approach would still work: a subtask you need to solve is how
to allocate a unique URL to a bunch of user ids and then redirect them
to the new URL when the timeout expires.

I second Colin's suggestion to use Javascript polling and the setTimeout
function, if it's not critical for the users to wait for 10 seconds to
be redirected to the right URL.

If it's very critical to redirect users quickly and waiting 10 secs is
too long, you can try 5 secs. You could also explore the approach of
implementing a push mechanism (I guess you can read discussions like
this one
http://stackoverflow.com/questions/219868/client-notification-should-i-use-an-ajax-push-or-poll
to get you started). Choosing between the two is a tradeoff of 1) how
much time do you want to spend coding/researching the topic, 2) what are
the actual user requirements for your app, 3) how much load would the
server take.

Good luck,
Martin

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[karan verma]

Thanks Martin and Colin. 

With your help and reading some stack overflow posts i've arrived at a solution that meets my need best. I'm posting it here so that it might be useful for other users. 

Since I wanted the users to be redirected in real time to a URL chosen by the admin or an algorithm in real time. I needed a solution that could push updates from the server to browser. Also sometimes, accompanied by events from the browser that may be relayed to other browser. 

The status quo presents three approaches: 

1. Nodejs server + Redis + Socket.io- The following blog post has all the details and was incredibly useful. http://liamkaufman.com/blog/2013/02/27/adding-real-time-to-a-restful-rails-app/

2. Server Sent Events and Ajax: The following post by the creator of Juggernaut explains how useful SSE could be and the reason why he killed Juggernaut. http://blog.alexmaccaw.com/killing-a-library

3. Pusher: pusher.com 

I started with the first option (Nodejs) after hearing a ton of good things about it. But finally realized that running Redis, Nodejs, Rails and Socket.io would be an overkill. A complicated solution. I also read about hosting issues with Socket.io on heroku. Although I use Amazon Ec2, i didn't wanted to take a chance. 

I decided against SSE because they are not supported Internet Explorer. Moreover unlike websockets they are half duplex and thus might not be the best approach to implement presence, chat rooms or any other application that requires full duplex communication. 

I finally decided on using the third alternative. Pusher, although being a paid option has a sandbox plan that suits my current needs. Moreover, it has great APIs for implementing realtime presence which greatly suits my purpose. The documentation is very easy to follow as well. 

I hope this helps someone in the future. 

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Karan