From: tamouse mailing lists <tamouse.lists@...>
Date: 2013-01-25T06:47:01+09:00
Subject: Re: How to DRY this up?

On Thu, Jan 24, 2013 at 11:55 AM, Robert Klemme
<shortcutter@googlemail.com> wrote:
> On Thu, Jan 24, 2013 at 6:29 PM, Jesús Gabriel y Galán
> <jgabrielygalan@gmail.com> wrote:
>> On Thu, Jan 24, 2013 at 6:18 PM, tamouse mailing lists
>> <tamouse.lists@gmail.com> wrote:
>>> I have some API calls I'm making, all with the following sort of
>>> begin-rescue-end wrapper:
>>>
>>> (pseudo-code)
>>>
>>> retries = 0
>>> begin
>>>   response = SomeAPI.api_method1(:request => { 'ThisId' => this_id })
>>> rescue API::Exception => e
>>>   retries.succ
>
> That #succ won't do anything because the result is not stored.
>
>>>   sleep( retries * 5 )
>>>   retry unless retries > 2
>
> You are sleeping too much here because after the last attempt you are
> sleeping as well.  Reason is that the decision to retry is made after
> sleeping. Grouping that in an if end would be better.
>
>>> end
>>>
>>> where there are multiple api_methods and request forms. Seems like I
>>> should be able to DRY this instead of doing this everywhere I have to
>>> make this sort of API call.
>>
>> You could create a method for it (untested):
>>
>> def call_with_retries obj, method, *args, retries=2
>>   begin
>>     response = obj.send(method, *args)
>>   rescue API::Exception => e
>>     retries -= 1
>>     sleep( retries * 5 )
>>     retry unless retries < 0
>>   end
>> end
>>
>> and call it like
>>
>> call_with_retries SomeApi, :api_method1, :request => { 'ThisId' => this_id }
>>
>> You could also pass the exception to rescue, or just rescue
>> StandardError, and also pass the time to sleep.
>> Hope this gives you some ideas.
>
> I'd rather put the code to invoke into a block because it gives much
> more flexibility and separates concerns:
>
> def retry_code(retries = 2)
>   count ||= 0
>   yield
> rescue API::Exception => e
>   count += 1
>
>   if count <= retries
>     sleep count * 5
>     retry
>   end
> end
>
> response = retry_code { SomeAPI.api_method1(:request => { 'ThisId' =>
> this_id }) }
>
> Kind regards
>
> robert
>
> --
> remember.guy do |as, often| as.you_can - without end
> http://blog.rubybestpractices.com/
>

Thanks, robert -- I very much like your version.