Database Triggered Events in Rails.

rubyonrails-talk
1

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!

2

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 - the search engine for concert, theatre & sports tickets.

David Harkness wrote: