How to Rescue Timeout Issues (Ruby, Rails)

How to rescue timeout issues (Ruby, Rails)

Depending on how you use the library, there are different ways to rescue the exception.

In the library

Assuming you created a wrapper to access some kind of web service, you can have the wrapper rescue the exception and always return a "safe" data.

In the action

If you call a specific method in the action and the method success is a requirement for the action, then you can rescue it in the action.
In the following example I rescue the error and show a specific template to handle the problem.

def action
  perform_external_call
rescue Timeout::Error => e
  @error = e
  render :action => "error"
end

In the controller

If the method call can occur in many different actions, you might want to use rescue_from.

class TheController < ApplicationController

  rescue_from Timeout::Error, :with => :rescue_from_timeout

  protected

  def rescue_from_timeout(exception)
    # code to handle the issue
  end

end

rescueing from a timeout error on ruby on rails

I normally like to include all the code in the rescue_from block for readability:

class ApplicationController < ActionController::Base
  ...
  rescue_from Timeout::Error do |e|
    ## log e if needed
    return redirect_to users_root_path

  end

  ...
end

That should work as intended (I don't even know if the return is needed)

rescue Exception not rescuing Timeout::Error in net_http

As you probably know already, calling raise inside a rescue block will raise the exception to the caller.
Since Timeout::Error is an Interrupt in ruby 1.8*, the timeout exception raised by net_http gets handled in the rescue SystemExit, Interrupt block rather than in the following rescue Exception => e.

To verify that Timeout::Error is an Interrupt, just evaluate Timeout::Error.ancestors. What you get out of that is the hierarchy of classes Timeout::Error inherits from.

*this is no longer the case in ruby1.9.

Ruby Timeout::timeout doesn't fire Exception and doesn't return what documented

Your code is correct

require 'timeout'
begin
  complete_results = Timeout.timeout(1) do      
   sleep(2)
  end
rescue Timeout::Error
  puts 'Print me something please'
end

does print out "print me something please".

Try the basic code as above. If that works, you have an issue in platform.search.

Rescue_from doesn't rescue Timeout::Error from views or helpers

I ran into the same problem. I'm using Rails 3 + Rack::Timeout and trying to rescue_from in ApplicationController.

I ended up using this ...

rescue_from Exception do |exception|
  if exception.is_a?(Timeout::Error) || /execution expired/ =~ exception.message
    # rescued from timeout error
  end
  raise
end

UPDATE

I patched the rack-timeout gem to properly return Timeout::Error. It was a threading issue. Official gem has been updated: https://github.com/kch/rack-timeout

The new preferred method is below. In general, it's not a great idea to rescue from Exception and should be avoided if possible.

class ApplicationController < ActionController::Base
  rescue_from Timeout::Error, with: :handle_timeout

  def handle_timeout(exception)
    # handle timeout error
  end
end

Handling Timeout error

Well, that's expected behaviour of Timeout. If the block takes too long, its execution gets terminated and an exception thrown.

You would probably like to catch the exception and handle it appropriately:

require 'timeout'
begin
  status = Timeout::timeout(5) {
    # Something that should be interrupted if it takes too much time...
  }
rescue Timeout::Error
  puts 'That took too long, exiting...'
end

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