Backgroundrb and Bj serve different purposes. The new backgroundrb is
a complete rewrite by Hemant that throws out drb and uses an event
driven styel of programming. It really is very stable now and it's
main focus is on doing jobs that require reporting status in your
rails app. Like if you want to fetch some news feeds and report a
progress bar via ajax polling in your app. Bdrb works very well for
this and other more real time background jobs.


  Bj is a work queue. You just shove jobs into the queue which is a
database table and the Bj daemon will run through them and call each
job one at a time. But you can also have Bj daemons on each node in a
cluster of servers and have them all pulling from the same queue. Bj
jobs are just shell commands. So your actual jobs can be ruby scripts,
shell scripts, or script/runner calls.  The main idea behind Bj is
that you could throw 100K jobs at it and it will just do them as fast
as it can one at a time without overwhelming the system all at once.


  So both of these tools are very solid now, they just serve different
purposes. Backgroiundrb is more for real time jobs and status reports
as well as having a very nice cron like scheduler for jobs.  Bj is
more of a work queue that is persistent.


  Hope that clears things up, Both of these tools are great for
different circumstances.

Cheers-
- Ezra Zygmuntowicz
-- Founder & Software Architect
-- ezra@engineyard.com
-- EngineYard.com

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I am sure that my queue has messages, but a call to ReceiveMessage returned none. What could be the problem?

Due to the distributed nature of the queue, a weighted random set of machines is sampled on a ReceiveMessage call. That means only the messages on the sampled machines are returned. If the number of messages in the queue is small (less than 1000), it is likely you will get fewer messages than you requested. If the number of messages in the queue is extremely small, you might not receive any messages in a particular ReceiveMessage response. Your application should be prepared to poll the queue until a message is received. Note that with the 2008-01-01 version of Amazon SQS, you’re charged for each request you make, so set your polling frequency with that in mind.