Can I delay HTTP response in rails?

Question

I'm new in Rails 4. I want to delay HTTP response.

I thought the 'respond_to' method is enable to respond to HTTP request.

However, When I removed the 'respond_to' method, The rails controller automatically responded to request.

Below is my step for this.

Send HTTP Request in view

[index.html.erb]
<script>
var ready = function() {
    alert('this is function');
}
var aquery = function() {
    $.ajax({
        type : "POST",
        url : "app/subaction",
    });
}

$(document).on('ready page:load', aquery); 
</script>

Receive HTTP Request in Controller

class AppController < ApplicationController
   def subaction
     (Nothing here...)
   end
end

subaction.js.erb

$('#div_id').empty().append("Complete response ...");

In this step, response was executed automatically although there is not "respond_to" method.

Can I delay the response ??? Can you explain request-response operation in rails ?

Thank you...

Why do you want to delay the respons? Are you playing mind games with the user? — Boris Stitnicky, Aug 11 '14 at 05:44
I want to update all user's view. In fact, users send ajax request to server and the server periodically respond to the request(in this part, I need to delay response). For example, In shopping mall site, If I buy all products, other users have to see sold out message in the site without refreshing WEB page. — JY Choi, Aug 11 '14 at 05:55
See if this helps you: http://stackoverflow.com/questions/21579023/get-live-logs-in-front-end-on-rails-application — Uri Agassi, Aug 11 '14 at 06:36
Um.. My intention is the concept like Timer.. So periodically respond to request..So, the answer about "until when" is the periodical response. I want to know why response was executed in controller without "respond_to", "render" method..Thank you.. — JY Choi, Aug 11 '14 at 08:01

score 1 · Accepted Answer · answered Aug 11 '14 at 11:06

The main reason Rails renders a response by default is because the documentation says so. Rails follows a philosophy of 'convention over configuration', which means it tries to help you out in ways that keep the code you write to a minimum. Most of the time you want your controller actions to render a view, so Rails does that for you.

You can use a number of techniques to delay responses. The simplest is to use Ruby's sleep method to introduce a delay:

class AppController < ApplicationController
   def subaction
     sleep 3 # Wait for 3 seconds before responding
   end
end

This might be useful when testing how your app behaves over a slow internet connection, but should probably be avoided in production code. Fast apps make happy users.

You could also use the ActionController::Live module, introduced in Rails 4.0.2. It allows you to stream data to the client, but consuming the stream can be tricky. jQuery waits for the response to complete before firing callbacks, so you'll have to use something else to process the stream.

This is similar to Websockets, an emerging streaming standard. There's some support available for websockets in Rails, but it's not universally supported by browsers.

Another alternative is to switch the delay to the frontend. You can use JavaScript's setTimeout or setInterval to call some code after a delay:

setTimeout(function() { 
    alert("I run once, after 4 seconds");
}, 4000);
setInterval(function() { 
    alert("I run every two seconds");
}, 2000);

If you're trying to check for updates, you might be tempted to use setInterval, but you may find it more flexible to use setTimeout to schedule a one-off check of the server. You can then include a time delay from the server which specifies how long to wait before asking again.

Can I delay HTTP response in rails?

1 Answers1