Re: [jruby-user] Concurrency issues with JRuby on Rails

Chason -

Interesting. I've done some fun stuff with concurrency under Rails, but
my stuff didn't deal with database connections in threads. So, I don't
don't have direct experience to help you here. This (long) blog post,
https://bibwild.wordpress.com/2014/07/17/activerecord-concurrency-in-rails4-avoid-leaked-connections/,
looks like it might be relevant to what you are seeing.

- Bruce

On Mon, Jan 19, 2015, at 05:11 PM, Chason Choate wrote:
> Hey Bruce,
>
> Thanks for the quick response.
> 1. The rails server is only taking 2-5 connections at this point in
>    time. We're testing atm. * No there are not many concurrent
>    connections. * The requests do take a significant amount of time
>    20+ seconds. (Returning json data hitting many different apis)
> 2. I am not aware of any AR calls outside of the typical rails
>    controller actions. * There may be a db leak but how do I tell? Is
>    there a variable, etc I can debug to print that info out? Remaining
>    connections perhaps?
> 3. I could increase the pool higher but with the info above there is
>    most likely a leak or something going wrong with the connection
>    pool.
>
> We are also using threading in the action that is causing the issue.
> But we have used the "with_connection" block before making any
> database calls in the thread.
>
> On Mon, Jan 19, 2015 at 3:43 PM, Bruce Adams
> <[email protected]> wrote:
>> __
>> It sounds like the twenty database connection you are allowing are
>> all in use for more than 15 seconds.
>>
>> Is your Rails server under much load? (Are there many, concurrent
>> requests? Are a bunch of those requests taking a long time (several
>> seconds) to complete?) Is there a chance that your application is
>> leaking database connections? That is, might their be code paths
>> where a connection is taken from the database connection pool, but
>> never returned to the pool?
>>
>> Can you increase the size of your database connection pool?
>>
>>
>> - Bruce
>>
>>
>> P.S. For what it's worth, I recommend a low checkout_timeout,
>>      specifically one second. I don't what a user request waiting
>>      around for resources. Fifteen seconds is a very long time for a
>>      user to wait for a web request. I'd rather give the user (and my
>>      own error logs) a message quickly when I run out of resources.
>>      With an error message, I get earlier notice that something isn't
>>      quite right.
>>
>> On Mon, Jan 19, 2015, at 04:28 PM, Chason Choate wrote:
>>> Hello there,
>>>
>>> I'm running into some concurrency issues and need some help. I'm
>>> currently using JRuby 1.7.12 and Rails 4.1.1. Every now and then i'm
>>> getting this error:
>>>
>>> ActiveRecord::ConnectionTimeoutError (could not obtain a database
>>> connection within 15.000 seconds (waited 15.001 seconds)):
>>> vendor/bundle/jruby/1.9/gems/activerecord-4.1.1/lib/active_record/connection_adapters/abstract/connection_pool.rb:190:in
>>> `wait_poll'
>>>
>>> Our database pool is set to 20 and a checkout_timeout of 15.
>>>
>>> Has anyone seen this issue before?
>>> --
>>> Thanks, Chason Choate
>>
>
>
>
> --
> Thanks, Chason Choate