AJAX responses

[Bob]

Does anyone know if it's possible to do multiple AJAX responses to a
single request in Rails? I did some googling but didn't find anything
extremely helpful.

Thanks.

[Marnen Laibow-Koser]

What do you mean? One HTTP request gets one response. That's the way
the protocol works

>
> Thanks.

Best,
-- 
Marnen Laibow-Koser
http://www.marnen.org
mar...@marnen.org
--
Posted via http://www.ruby-forum.com/.

[Peter De Berdt]

On 10 Feb 2010, at 17:18, Marnen Laibow-Koser wrote:

Does anyone know if it's possible to do multiple AJAX responses to a

single request in Rails?  I did some googling but didn't find anything

extremely helpful.

What do you mean?  One HTTP request gets one response.  That's the way 
the protocol works

Indeed, every HTTP request only yields one response. What you are looking for is a PeriodicalExecuter or PeriodicalUpdater (javascript polling every xx seconds). Another way to go is a push notification system, which is more difficult to implement and host (forget about hosting it on a shared host). Juggernaut or Comet should help you out there. But unless you really know what you are doing, the periodical execution way is going to give you the least amount of problems.

Best regards

Peter De Berdt

[Bob]

I have a class that compares invoice totals for a month and calculates
the dollars saved. The downside is it takes about 1 second per
invoice per month to calculate so it's taking a considerable amount of
time to display a complete report especially if you run it for a two
year period (48 seconds). What I was hoping to do is to make an AJAX
request for the report and respond with each row (or month in this
case) of the comparison table as they finish calculating. I had a
feeling this would be pretty problematic to do...

[Peter De Berdt]

In my opinion, there's three ways to go about this:

1. Pregenerate reports in low traffic/low CPU usage times, like overnight. Since you are making monthly invoicing reports, the reports should stay the same anyway. When the user requests a certain range, assemble the cached pieces into on nice report.

2. Fire a PeriodicalExecuter to a controller method. The first time, it starts the report generation in a background process, every subsequent request will load the generated report lines into the view

3. Use Juggernaut or Comet to push the data to the client. Fire an event to start the report generation in a background process and then route to the clients that are subscribed to the right Juggernaut/Comet channel.

Personally, unless realtime reports are an absolute necessity, I would just go for a nightly report generation cron tab. It will provide the best experience to your end user and won't put a serious strain on the server overall during peak traffic times.