# Database Triggered Events in Rails

**URL:** <https://www.ruby-forum.com/t/database-triggered-events-in-rails/132308>\
**Category:** Rails\
**Created:** [March 19, 2008, 1:35am UTC](https://www.ruby-forum.com/t/database-triggered-events-in-rails/132308 "2008-03-19T01:35:19Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![divotdave](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/bbe5ce/32.png) [@divotdave](https://www.ruby-forum.com/u/divotdave)\
**Post date:** [March 19, 2008, 1:35am UTC](https://www.ruby-forum.com/t/database-triggered-events-in-rails/132308/1 "2008-03-19T01:35:19Z")

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I’m creating a message queue system, (think JMS message queue)

Basically, I’ll be firing off an http request as soon as a row appears  
in a database.

Now in past implementations I’ve done the following.

1. Polled the database every 0.10 seconds.
2. If something was there to work, I’d tag it as complete.
3. Create a separate thread. (no further database hits will made)
4. Run my Net::HTTP.get\_response(), which takes from 0.00001 to 600  
seconds to complete.
5. Write output to some log file.

What’s gotten me into trouble now, is I want to do touch the database.  
Which creates all sorts of havoc in rails when threaded.

I’m pondering using BackgroundDB, but it looks like it’s meant for slow  
running tasks, not thousands of messages flying back and forth.

I was also thinking of, not touching the database in the thread, but  
posting the results back to a separate instance of the rails app, and  
let that instance handle the writes to the database. This seems kludgey  
though.

I’ve heard that merb, and some of those are threadsafe, maybe I can have  
this piece of it, using that instead?

Or perhaps something else.

Thanks for any response!

---

<div class="post-metadata">

**Author:** ![divotdave](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/bbe5ce/32.png) [@divotdave](https://www.ruby-forum.com/u/divotdave)\
**Post date:** [March 19, 2008, 2:57am UTC](https://www.ruby-forum.com/t/database-triggered-events-in-rails/132308/2 "2008-03-19T02:57:09Z")

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Hi David,

I may have not quite understood what you are trying to achieve, but I’ll  
have a bash at this.

Rather than using rails for the whole solution, you could try a daemon  
process [could be ruby, php, python, java, C… does not really matter]  
monitoring your db, when you find an interesting record, then execute  
another thread to handle both the db updates & the request to your rails  
site.

Another way, if your db allows it, you could try a trigger that performs  
the db operations, then shelling out to a command prompt to execute the  
http request to your rails site [unless you can access a http request  
within your db’s psql]

Both ways would work on windows & unix, and would be simplier & more  
reliable in my opinion.

rgds,

- matt.

[http://www.tickex.com](http://www.tickex.com) - the search engine for concert, theatre & sports  
tickets.

David H. wrote:

> I’m creating a message queue system, (think JMS message queue)
> 
> Basically, I’ll be firing off an http request as soon as a row appears  
> in a database.
> 
> Now in past implementations I’ve done the following.
> 
> 1. Polled the database every 0.10 seconds.
> 2. If something was there to work, I’d tag it as complete.
> 3. Create a separate thread. (no further database hits will made)
> 4. Run my Net::HTTP.get\_response(), which takes from 0.00001 to 600  
> seconds to complete.
> 5. Write output to some log file.
> 
> What’s gotten me into trouble now, is I want to do touch the database.  
> Which creates all sorts of havoc in rails when threaded.
> 
> I’m pondering using BackgroundDB, but it looks like it’s meant for slow  
> running tasks, not thousands of messages flying back and forth.
> 
> I was also thinking of, not touching the database in the thread, but  
> posting the results back to a separate instance of the rails app, and  
> let that instance handle the writes to the database. This seems kludgey  
> though.
> 
> I’ve heard that merb, and some of those are threadsafe, maybe I can have  
> this piece of it, using that instead?
> 
> Or perhaps something else.
> 
> Thanks for any response!